LTC2903-1 Datasheet by Analog Devices Inc.

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1
LTC2903-1
29031f a
■
Multivoltage Systems
■
Optical Networking Systems
■
Cell Phone Base Stations
■
Network Servers
Precision Quad Supply
Monitor in 6-Lead SOT-23
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
Ultralow Voltage Reset: V
CC
= 0.5V Guaranteed
■
Monitor Four Inputs Simultaneously
3.3V, 2.5V, 1.8V, ADJ (LTC2903-A1)
5V, 3.3V, 2.5V, 1.8V (LTC2903-B1)
5V, 3.3V, 1.8V, –5.2V (LTC2903-C1)
3.3V, ADJ, ADJ, ADJ (LTC2903-D1)
5V, ADJ, ADJ, ADJ (LTC2903-E1)
■
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage over Temperature
■
10% (A1, B1, C1) and 5% (D1, E1) Undervoltage
Monitoring
■
Low Supply Current: 20µA Typical
■
200ms Reset Time Delay
■
Active Low Open-Drain RST Output
■
Power Supply Glitch Immunity
■
Low Profile (1mm) SOT-23 (ThinSOT
TM
) Package
The LTC
®
2903-1 monitors up to four supply voltages. The
common reset output remains low until all four inputs
have been in compliance for 200ms. Voltage thresholds
maintain ±1.5% accuracy over temperature (with respect
to the monitored voltage). The LTC2903-1 features an
open-drain RST output with a weak internal pullup.
Internal supply voltage (V
CC
) is generated from the greater
voltage on the V1, V2 inputs. V
CC
= V1 for LTC2903-D1 and
LTC2903-E1. The RST output is guaranteed to sink at least
5µA (V
OL
= 0.15V) for V
CC
down to 0.5V and will typically
conduct current down to 0V. Quiescent current is 20µA
typical, making the LTC2903-1 ideal for power conscious
systems. The LTC2903-1 is available in a 6-lead low profile
(1mm) SOT-23 package.
ThinSOT is a trademark of Linear Technology Corporation.
V
IN
, INPUT SUPPLY VOLTAGE (V)
0
RESET PIN VOLTAGE (V)
0.06
0.08
0.10
0.8
2903 TA01b
0.04
0.02
0.05
0.07
0.09
0.03
0.01
00.20.1
1µA
0.40.3 0.6 0.7 0.9
0.5 1
2µA
5µA
20µA
V
IN
= V1 = V2 = V3
LTC2903-B1
10µA
Low Voltage Reset Pull-Down Performance
vs External Pull-Up Current and Input Supply Voltage
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
V1
GND
V2
RST
V4
V3
LTC2903-B1
C1
0.1µF
1.8V
C2
0.1µF
2903 TA01
2.5V
3.3V
5V
DC/DC
CONVERTER
SYSTEM
LOGIC
HBSOLUTE flXI U flflTl G WU UUU L7 LJFJW
2
LTC2903-1
29031f a
ABSOLUTE MAXIMUM RATINGS
W
WW
U
PACKAGE/ORDER INFORMATION
W
UU
V1, V2 ...................................................... –0.3V to 6.5V
V3 ................................................. 2.7V or (V
CC
+ 0.3V)
V4 (LTC2903-A1, -B1, -D1, -E1) ...............–0.3V to 6.5V
V4 (LTC2903-C1) .................................... –6.5V to 0.3V
RST ........................................................ – 0.3V to 6.5V
Operating Temperature Range
LTC2903C-X1 .......................................... 0°C to 70°C
LTC2903I-X1 ...................................... –40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART NUMBER
(Notes 1, 2, 3)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
LTC2903CS6-A1
LTC2903CS6-B1
LTC2903CS6-C1
LTC2903CS6-D1
LTC2903CS6-E1
LTC2903IS6-A1
LTC2903IS6-B1
LTC2903IS6-C1
LTC2903IS6-D1
LTC2903IS6-E1
T
JMAX
= 125°C, θ
JA
= 230°C/W
V1 1
GND 2
V2 3
6 RST
5 V4
4 V3
TOP VIEW
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
S6 PART MARKING
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT33
3.3V, 10% Reset Threshold V1 Input Threshold ●2.871 2.921 2.970 V
V
RT25
2.5V, 10% Reset Threshold V2 Input Threshold ●2.175 2.213 2.250 V
V
RT18
1.8V, 10% Reset Threshold V3 Input Threshold ●1.566 1.593 1.620 V
V
RTA
Adjustable Reset Threshold V4 Input Threshold ●0.492 0.500 0.508 V
(LTC2903-A1) The ● denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT50
5V, 10% Reset Threshold V1 Input Threshold ●4.350 4.425 4.500 V
V
RT33
3.3V, 10% Reset Threshold V2 Input Threshold ●2.871 2.921 2.970 V
V
RT25
2.5V, 10% Reset Threshold V3 Input Threshold ●2.175 2.213 2.250 V
V
RT18
1.8V, 10% Reset Threshold V4 Input Threshold ●1.566 1.593 1.620 V
(LTC2903-B1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC = 5V unless otherwise noted.
LTAFV
LTAJN
LTAJQ
LTBMX
LTBMZ
LTAFW
LTAJP
LTAJR
LTBMY
LTBNB
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT50
5V, 10% Reset Threshold V1 Input Threshold ●4.350 4.425 4.500 V
V
RT33
3.3V, 10% Reset Threshold V2 Input Threshold ●2.871 2.921 2.970 V
V
RT18
1.8V, 10% Reset Threshold V3 Input Threshold ●1.566 1.593 1.620 V
V
RT52N
–5.2V, 10% Reset Threshold V4 Input Threshold ●–4.524 –4.602 –4.680 V
(LTC2903-C1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC = 5V unless otherwise noted.
L7UHN§GB
3
LTC2903-1
29031f a
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
V1
V1 Input Current (Note 4) V1 = 3.3V (LTC2903-A1, LTC2903-D1) ●20 80 µA
V1 = 5V (LTC2903-B1, LTC2903-C1, ●25 80 µA
LTC2903-E1)
I
V2
V2 Input Current (Note 4) V2 = 2.5V (LTC2903-A1) ●830 µA
V2 = 3.3V (LTC2903-B1, LTC2903-C1) ●10 30 µA
V2 = 0.55V (LTC2903-D1, LTC2903-E1) ●±30 nA
I
V3
V3 Input Current V3 = 1.8V (LTC2903-A1, LTC2903-C1) ●830 µA
V3 = 2.5V (LTC2903-B1) ●10 30 µA
V3 = 0.55V (LTC2903-D1, LTC2903-E1) ●±30 nA
I
V4
V4 Input Current V4 = 0.55V (LTC2903-A1) ●±30 nA
V4 = 1.8V (LTC2903-B1) ●24 µA
V4 = –5.2V (LTC2903-C1) ●–3 –6 µA
V4 = 0.55V (LTC2903-D1, LTC2903-E1) ●±30 nA
t
RST
Reset Time-Out Period ●140 200 260 ms
t
UV
V
X
Undervoltage Detect to RST V
X
Less Than Threshold V
RTX
by 150 µs
More Than 1%
V
OH
Output Voltage High RST (LTC2903-1) (Note 5) I
RST(DN)
= –1µA (LTC2903-A1, ●V2 – 1 V
LTC2903-B1, LTC2903-C1)
(LTC2903-D1, LTC2903-E1) ●V1 – 1 V
V
OL
Output Voltage Low RST (Note 6) V
CC
= 0.2V, I
RST
= 0.1µA●560 mV
V
CC
= 0.5V, I
RST
= 5µA●10 150 mV
V
CC
= 1V, I
RST
= 200µA●25 300 mV
V
CC
= 3V, I
RST
= 2500µA●100 300 mV
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 3.3V unless otherwise noted.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
Note 3: The internal supply voltage (V
CC
) is generated from the greater
voltage on the V1 and V2 inputs. V
CC
= V1 for options D1 and E1.
Note 4: Under typical operating conditions, quiescent current is drawn
from the V1 input. When V2 exceeds V1, V2 supplies the quiescent
current. V1 only for options D1 and E1.
Note 5: The RST output pin on the LTC2903-1 has an internal pull-up to
V2 (for options A1, B1 and C1) of typically 10µA. However, for faster rise
times or for V
OH
voltages greater than V2, use an external pull-up resistor.
The internal pull-up is connected to V1 for options D1 and E1.
Note 6: For options A1, B1 and C1, the RST pulldown current is derived
from V1, V2 and V3. For options D1 and E1, pulldown strength is derived
from V1.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT33
3.3V, 5% Reset Threshold V1 Input Threshold ●3.036 3.086 3.135 V
V
RTAV2
V2 Adjustable Threshold V2 Input Threshold ●0.492 0.500 0.508 V
V
RTAV3
V3 Adjustable Threshold V3 Input Threshold ●0.492 0.500 0.508 V
V
RTAV4
V4 Adjustable Threshold V4 Input Threshold ●0.492 0.500 0.508 V
(LTC2903-D1) The ● denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT50
5V, 5% Reset Threshold V1 Input Threshold ●4.600 4.675 4.750 V
V
RTAV2
V2 Adjustable Threshold V2 Input Threshold ●0.492 0.500 0.508 V
V
RTAV3
V3 Adjustable Threshold V3 Input Threshold ●0.492 0.500 0.508 V
V
RTAV4
V4 Adjustable Threshold V4 Input Threshold ●0.492 0.500 0.508 V
(LTC2903-E1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC = 5V unless otherwise noted.
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LTC2903-1
29031f a
TYPICAL PERFOR A CE CHARACTERISTICS
UW
5V Threshold Voltage
vs Temperature
TEMPERATURE (°C)
–50
4.350
THRESHOLD VOLTAGE, V
RT50
(V)
4.375
4.400
4.450
4.425
4.500
4.475
–25 02550
29031 G01
75 100
TEMPERATURE (°C)
–50
2.875
THRESHOLD VOLTAGE, V
RT33
(V)
2.900
2.925
2.950
2.975
–25 02550
29031 G02
75 100
TEMPERATURE (°C)
–50
THRESHOLD VOLTAGE, V
RT25
(V)
2.250
2.235
2.220
2.205
2.190
2.175
–25 02550
29031 G03
75 100
3.3V Threshold Voltage
vs Temperature
2.5V Threshold Voltage
vs Temperature
1.8V Threshold Voltage
vs Temperature
ADJ Threshold Voltage
vs Temperature
–5.2V Threshold Voltage
vs Temperature
TEMPERATURE (°C)
–50
THRESHOLD VOLTAGE, V
RT18
(V)
1.625
1.615
1.595
1.605
1.575
1.585
1.565 –25 02550
29031 G04
75 100
TEMPERATURE (°C)
–50
THRESHOLD VOLTAGE, V
RTA
(V)
0.510
0.505
0.500
0.495
0.490 –25 02550
29031 G05
75 100
TEMPERATURE (°C)
–50
THRESHOLD VOLTAGE, V
RT52N
(V)
–4.530
–4.555
–4.605
–4.580
–4.630
–4.655
–4.680 –25 02550
29031 G06
75 100
Supply Currents
vs Temperature (LTC2903-A1)
TEMPERATURE (°C)
–50
0
IVX (µA)
5
10
15
20
IV1
IV2
IV3
30
–25 02550
29031 G07
75 100
25
V1 = 3.3V
V2 = 2.5V
V3 = 1.8V
Supply Currents
vs Temperature (LTC2903-B1)
TEMPERATURE (°C)
–50
0
IVX (µA)
5
10
15
20
IV1
IV2 IV3
IV4
30
–25 02550
29031 G08
75 100
25
V1 = 5V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
Supply Currents
vs Temperature (LTC2903-C1)
TEMPERATURE (°C)
–50
30
25
20
15
10
5
0
–5 25 75
29031 G09
–25 0 50 100
I
VX
(µA)
I
V1
I
V2
I
V3
I
V4
V1 = 5V
V2 = 3.3V
V3 = 1.8V
V4 = –5.2V
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LTC2903-1
29031f a
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Transient Duration
vs Comparator Overdrive
Reset Time-Out Period
vs Temperature
RST Output Voltage with 10k
Pull-Up to V1
RST Output Voltage with
10k Pull-Up to V1
RESET COMPARATOR OVERDRIVE (% OF VRTX)
0.1
250
TYPICAL TRANSIENT DURATION (µs)
300
350
400
1 10 100
29031 G10
200
150
50
0
100
RESET OCCURS
ABOVE CURVE
TEMPERATURE (°C)
–50
140
RESET TIME-OUT PERIOD, tRST (ms)
160
180
200
220
260
–25 02550
29301 G11
75 100
240
V1 (V)
0
RST OUTPUT VOLTAGE (V)
3.0
4.0
5.0
4
29031 G12
2.0
1.0
2.5
3.5
4.5
1.5
0.5
010.5 21.5 3 3.5 4.5
2.5 5
V1 = V2 = V3
LTC2903-B1, -C1
V1 (V)
0
RST OUTPUT VOLTAGE (V)
0.15
0.20
0.25
0.30
0.8
29301 G13
0.10
0.05
00.2 0.4 0.6 1.0
0.7
0.1 0.3 0.5 0.9
V1 ONLY
V1 = V2 = V3
Low Voltage Reset Pull-Down
Performance vs External Pull-Up
Current and Input Supply Voltage
V
IN
, INPUT SUPPLY VOLTAGE (V)
0
RESET PIN VOLTAGE (V)
0.06
0.08
0.10
0.8
29031 G14
0.04
0.02
0.05
0.07
0.09
0.03
0.01
00.20.1
1µA
0.40.3 0.6 0.7 0.9
0.5 1
2µA
5µA
20µA
V
IN
= V1 = V2 = V3
10µA
RST Current Sink Capability
vs VCC
V
CC
(V)
0
I
RST
(mA)
9
12
15
1.5 2.5 5
29031 G15
6
3
00.5 1 23 3.5 4 4.5
V
OL
= 0.4V
V
OL
= 0.2V
RST Voltage Output Low
vs RST Sink Current
IRST (mA)
0
0
VOL (V)
0.3
0.9
1.2
1.5
10 20 25 45
29031 G16
0.6
515 30 35 40
LTC2903-A1, -E1
V1 = 3.3V 85°C25°C
–45°C
I
RST
(mA)
0
0
V
OL
(V)
0.3
0.9
1.2
1.5
10 20 60
29031 G16
0.6
30 40 50
LTC2903-B1, -C1, -D1
V1 = 5V
85°C
25°C
–45°C
RST Voltage Output Low
vs RST Sink Current
Supply Currents vs Temperature
TEMPERATURE (°C)
–50
0
IV1 (µA)
5
10
15
20
25
–25 02550
29031 G20
75 100
LTC2903-E1
LTC2903-D1
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LTC2903-1
29031f a
V
RST
(V)
0
I
RST
(µA)
29031 G22
–20
–10
12
0
–80
–70
–60
–50
–40
–30
3456
LTC2903-E1
LTC2903-D1
TYPICAL PERFOR A CE CHARACTERISTICS
UW
RST Pull-Up Current vs V2
RST Pull-Up Current vs External
Pull-Down Voltage on RST
V2 (V)
0
IRST (µA)
–50
–70
–90
4
29031 G18
–30
–10
–40
–60
–80
–20
010.5 21.5 3 3.5 4.5
2.5 5
VRT25 VRT33
LTC2903-A1, -B1, -C1
V1, V3, V4 ABOVE THRESHOLD
V
RST
(V)
0
I
RST
(µA)
–35
1.5
29031 G19
–20
–10
0.5 1 2
–5
0
–40
–30
–25
–15
2.5 3 3.5
LTC2903-B1, -C1
LTC2903-A1
RST Pull-Up Current vs V1
RST Pull-Up Current vs External
Pull-Down Voltage on RST
V1 (V)
0
I
RST
(µA)
–50
–70
–80
4
29031 G21
–30
–10
–40
–60
–20
010.5 21.5 3 3.5 4.5
2.5 5.55
LTC2903-D1, -E1
V2, V3, V4 ABOVE THRESHOLD
LTC2903-D1
LTC2903-E1
L7UHN§GB
7
LTC2903-1
29031f a
TI I G DIAGRA
UWW
V
RTX
t
UV
t
RST
1.5V
29031 TD
V
X
RST
UU
U
PI FU CTIO S
V1 (Pin 1): Voltage Input 1. Internal V
CC
is generated from
the greater voltage on the V1 and V2 inputs. V
CC
= V1 for
options D1 and E1. Bypass this pin to ground with a 0.1µF
(or greater) capacitor.
GND (Pin 2): Ground.
V2 (Pin 3): Voltage Input 2. Internal V
CC
is generated from
the greater voltage on the V1 and V2 inputs. V
CC
= V1 for
options D1 and E1. For option A1, B1, C1 bypass this pin
to ground with a 0.1µF (or greater) capacitor. V2 is an
adjustable input for options D1 and E1. See Table 1b for
recommended ADJ resistor values.
V3 (Pin 4): Voltage Input 3. This input assists the RST pull-
down circuitry below 1V (for options A1, B1 and C1 only).
V3 is an adjustable input for options D1 and E1. See Table
1b for recommended ADJ resistor values.
V4 (Pin 5): Voltage Input 4. Table 1 lists the recommended
ADJ resistor values for options A1, B1 and C1. See Table
1b for options D1 and E1.
RST (Pin 6): Reset Logic Output. Pulls low when any volt-
age input is below reset threshold and held low for 200ms
after all voltage inputs exceed threshold. The pin contains
a weak pull-up to V2 (V1 for options D1 and E1). Use an
external pull-up for faster rise times or output voltages
greater than V2 (V1 for options D1 and E1).
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8
LTC2903-1
29031f a
(LTC2903-C1)
BLOCK DIAGRA S
W
1
V1
3
V2
4
V3
5
V4
2
GND
–
+
–
+
–
+
–
+
RESET DELAY GENERATOR
200ms
DELAY
LOW VOLTAGE
PULL-DOWN
BANDGAP
REFERENCE
V1
V2
V3
V2
RST
10µA
6
29031 BD3
POWER
DETECT
V1
V2
V
CC
V1
V2
V3
V4
5V
3.3V
1.8V
–5.2V
MONITORED VOLTAGES
(LTC2903-A1, LTC2903-B1)
1
V1
3
V2
4
V3
5
V4
2
GND
–
+
–
+
–
+
–
+
RESET DELAY GENERATOR
200ms
DELAY
LOW VOLTAGE
PULL-DOWN
BANDGAP
REFERENCE
V1
V2
V3
V4
A1
3.3V
2.5V
1.8V
ADJ
B1
5V
3.3V
2.5V
1.8V
MONITORED VOLTAGES
V1
V2
V3
V2
RST
10µA
6
29031 BD1
POWER
DETECT
V1
V2
V
CC
0.5V
BLOCK DIHGB — —Vcc zooms ,3 > DELAV LOW VOLTAGE V' _ PULLVDDWN @ , :53 MOMTURED VDLTAGES m v1 3 av 5v v2 ADJ ADJ v3 ADJ ADJ BAMDGAP ADJ ADJ «E { REFERENCE w residesibe L7LJHN§GB zsnzu a 9
9
LTC2903-1
29031f a
(LTC2903-D1, LTC2903-E1)
BLOCK DIAGRA S
W
V
CC
1
V1
3
V2
4
V3
5
V4
2
GND
–
+
–
+
–
+
–
+
RESET DELAY GENERATOR
200ms
DELAY
LOW VOLTAGE
PULL-DOWN
BANDGAP
REFERENCE
V1
V2
V3
V4
D1
3.3V
ADJ
ADJ
ADJ
E1
5V
ADJ
ADJ
ADJ
MONITORED VOLTAGES
V1
V1
RST
10µA
6
29031 BD2
POWER
DETECT
V1
0.5V
APPLICATIO S I FOR ATIO
WUUU
Power-Up
The LTC2903-1 issues a logic low on the RST output when
an input supply voltage resides below the prescribed
threshold voltage. Ideally, the RST logic output would
remain low with the input supply voltage down to zero
volts. Most supervisors lack pull-down capability below
1V. The LTC2903-1 power supply supervisors incorporate
a new low voltage pull-down circuit that can hold the RST
line low with as little as 200mV of input supply voltage on
V1, V2 or V3 (V1 only for options D1 and E1). The pull-down
circuit helps maintain a low impedance path to ground,
reducing the risk of floating the RST node to undetermined
voltages. Such voltages may trigger external logic causing
erroneous reset operation(s). Furthermore, a mid-scale
voltage could cause external circuits to operate in the
middle of their voltage transfer characteristic, consuming
more quiescent current than normal. These conditions
could cause serious system reliability problems.
When V1, V2 and V3 are ramped simultaneously (for
options A1, B1 and C1 only), the reset pull-down current
increases up to three times the current that may be pulled
with a single input. Figure 1 demonstrates the reset pin
V
CC
(V)
10
I
RST
(µA)
1000
10000
0 0.8 1.2
29031 F01
1
0.40.2 1.00.6
100 V1 = V2 = V3 V1 ONLY
T
A
= 25°C
V
RST
= 0.3V
CC
Figure 1. RST Pull-Down Current vs VCC
M'PHmoN I : PART / L7L'Um
10
LTC2903-1
29031f a
APPLICATIO S I FOR ATIO
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Triple Adjustable Options (LTC2903-D1, LTC2903-E1)
LTC2903-D1 and LTC2903-E1 provide 3 adjustable in-
puts: V2, V3 and V4. The V1 threshold is 3.086V (3.3V,
5%) for option D1 and 4.675 (5V, 5%) for option E1. For
each supply monitored by an adjustable input, connect an
external resistor divider (R1 and R2) between the positive
voltage being sensed and ground. The tap point for each
divider is then connected to each adjustable input. All
adjustable inputs are compared to an internal 0.5V
reference.
Figure 3 shows how each adjustable input is configured.
Calculate the trip voltage from:
VV
R
R
TRIP
=+
⎛
⎝
⎜⎞
⎠
⎟
05 1 1
2
.
Figure 3. Setting the Positive Adjustable Trip Point
V1 (V)
0
0
RST OUTPUT VOLTAGE (V)
0.1
0.3
0.4
0.5
0.7
0.1 0.5 0.7
29031 F02
0.2
0.6
0.4 0.9 1.0
0.2 0.3 0.6 0.8
TA = 25°C
V1 ONLY
COMPETITION
PART
V1 = V2 = V3
–
+
0.5V
29031 F03
V4
V
TRIP
R1
LTC2903-A1
R2
+
–
Figure 2. RST Output Voltage with a 10k Pull-Up to V1
(Enlarged Area of Detail)
current sinking ability for single supply and triple supply-
tracking applications. Figure 2 shows a detailed view of the
reset pin voltage with a 10k pull-up resistor to V1.
The LTC2903-1 supervisors derive their internal supply
voltage (V
CC
) automatically from the greater voltage on the
V1 and V2 inputs (V
CC
= V1 for options D1 and E1). With
all supply inputs above threshold, the quiescent current
drawn from V
CC
is 20µA (typ).
Supply Monitoring
The LTC2903-1 accurately monitors four inputs in a small
6-lead SOT-23 package. The low voltage reset output
includes an integrated 200ms reset delay timer. The reset
line pulls high 200ms after all voltage inputs exceed their
respective thresholds. The reset output remains low dur-
ing power-up, power-down and brownout conditions on
any of the voltage inputs.
as L7UHN§GB
11
LTC2903-1
29031f a
Table 1a contains suggested 1% resistor values for the
ADJ inputs to obtain nominal –11.5% thresholds. Connect
unused supervisor inputs to the highest supply voltage
available.
Table 1a. Suggested 1% Resistor Values for the –11.5% ADJ Inputs
V
SUPPLY
(V) V
TRIP
(V) R1 (kΩ) R2(kΩ)
12 10.75 2050 100
10 8.95 1690 100
8 7.15 1330 100
7.5 6.7 1240 100
6 5.38 976 100
5 4.435 787 100
3.3 2.935 487 100
3 2.66 432 100
2.5 2.2 340 100
1.8 1.605 221 100
1.5 1.325 165 100
1.2 1.065 113 100
1 0.884 76.8 100
0.9 0.795 59 100
Table 1b contains suggested 1% resistor values for the
ADJ inputs to obtain nominal –6.5% thresholds.
Table 1b. Suggested 1% Resistor Values for the –6.5% ADJ Inputs
V
SUPPLY
(V) V
TRIP
(V) R1 (kΩ) R2(kΩ)
12 11.25 2150 100
10 9.4 1780 100
8 7.5 1400 100
7.5 7 1300 100
6 5.6 1020 100
5 4.725 845 100
3.3 3.055 511 100
3 2.82 464 100
2.5 2.325 365 100
1.8 1.685 237 100
1.5 1.410 182 100
1.2 1.120 124 100
1.0 0.933 86.6 100
0.9 0.840 68.1 100
0.8 0.750 49.9 100
0.7 0.655 30.9 100
0.6 0.561 12.1 100
Implications of Threshold Accuracy
Specifying system voltage margin for worst-case opera-
tion requires consideration of three factors: power supply
tolerance, IC supply voltage tolerance and supervisor re-
set threshold accuracy. Highly accurate supervisors ease
the design challenge by decreasing the overall voltage
margin required for reliable system operation. Consider a
5V system with a ±10% power supply tolerance band.
System ICs powered by this supply must operate reliably
within this band (and a little more, as explained below).
The bottom of the supply tolerance band, at 4.5V (5V –
10%), is the exact voltage at which a
perfectly accurate
supervisor generates a reset. Such a perfectly accurate
supervisor does not exist—the actual reset threshold may
vary over a specified band (±1.5% for the LTC2903-1 su-
pervisors). Figure 4 shows the typical relative threshold
accuracy for all four inputs, over temperature.
With this variation of reset threshold in mind, the nominal
reset threshold of the supervisor resides
below
the mini-
mum supply voltage, just enough so that the reset thresh-
old band and the power supply tolerance bands do not
overlap. If the two bands overlap, the supervisor could
generate a false or nuisance reset when the power supply
remains within its specified tolerance band (say, at 4.6V).
Adding half of the reset threshold accuracy spread (1.5%)
to the ideal 10% thresholds puts the LTC2903-1 thresh-
olds at 11.5% (typ) below the nominal input voltage. For
example, the 5V typical threshold is 4.425V, or 75mV
below the ideal threshold of 4.500V. The guaranteed
threshold lies in the band between 4.500V and 4.350V
over temperature.
APPLICATIO S I FOR ATIO
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Figure 4. LTC2903 Typical Threshold Accuracy vs Temperature
TEMPERATURE (°C)
–50
–1.5
TYPICAL THRESHOLD ACCURACY (%)
–1.0
–0.5
0
0.5
25 75 100
29031 F04
1.0
1.5
–25 0 50
Ann am Sun 25a mm in WPIDALTRANSIENT DURATION is) n m I m w RESET COMPARATOR OVERDRNE ('34, OF vm) Figure 5. Typical Transient Duralinn vs 0v Required in Trip Camparalnr 12
12
LTC2903-1
29031f a
APPLICATIO S I FOR ATIO
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The powered system must work reliably down to the
lowest voltage in the threshold band or risk malfunction
before the reset line falls. In the 5V example, using the
1.5% accurate supervisor, the system ICs must work
down to 4.35V. System ICs working with a ±2.5% accurate
supervisor must operate down to 4.25V, increasing the
required system voltage margin and the probability of
system malfunction.
In any supervisory application, supply noise riding on the
monitored DC voltage can cause spurious resets, particu-
larly when the monitored voltage approaches the reset
threshold. A less than desirable but commonly used
technique used to mitigate this problem adds hysteresis to
the input comparator. The amount of added hysteresis,
usually specified as a percentage of the trip threshold,
effectively degrades the advertised accuracy of the part.
To maintain high accuracy, the LTC2903-1 does not use
hysteresis.
To minimize spurious resets while maintaining threshold
accuracy, the LTC2903-1 employs two forms of noise
filtering. The first line of defense incorporates proprietary
tailoring of the comparator transient response. Transient
events receive electronic integration in the comparator
and must exceed a certain magnitude and duration to
cause the comparator to switch. Figure 5 illustrates the
typical transient duration versus comparator overdrive
(as a percentage of the trip threshold V
RT
) required to trip
the comparators. Once any comparator is switched, the
reset line pulls low. The reset time-out counter starts once
all inputs return above threshold. The nominal reset delay
time is 200ms. The counter clears whenever any input
drops back below threshold. This reset delay time effec-
tively provides further filtering of the voltage inputs. A
noisy input with frequency components of sufficient mag-
nitude above f = 1/t
RST
= 5Hz holds the reset line low,
preventing oscillatory behavior on the reset line.
Although all four comparators have built-in glitch filtering,
use bypass capacitors on the V1 and V2 inputs because
the greater of V1 or V2 supplies the V
CC
(options A1, B1
and C1) for the part (a 0.1µF ceramic capacitor satisfies
most applications). Apply filter capacitors on the V3 and
V4 inputs in extremely noisy situations. Options D1 and E1
require a bypass capacitor only on V1. Apply filter capaci-
tors on V2, V3 and V4 adjustable inputs in extremely noisy
situations.
Reset Output Rise and Fall Time Estimation
The reset output line contains a weak pull-up current
source to the V2 supply (V1 for options D1 and E1). Use
an external pull-up resistor when the output needs to pull
to another voltage and/or when the reset output needs a
faster rise time. The open-drain output allows for wired-
OR connections when more than one signal needs to pull
down on the reset line. Estimate output rise time for the
open-drain output without an external pull-up using:
t
RISE
≈ 2.2 • R
PU
• C
LOAD
where R
PU
is the on-resistance of the pull-up transistor
and C
LOAD
is the external load capacitance on the pin. At
room temperature, the average R
PU
is approximately
50kΩ. When externally pulling up to voltages higher than
V2 (V1 for options D1 and E1), an internal network
automatically protects the weak pull-up circuitry from
reverse currents.
The reset output has very strong pull-down capability.
Estimate the output fall time using:
t
FALL
≈ 2.2 • R
PD
• C
LOAD
where R
PD
is the on-resistance of the pull-down transistor
and C
LOAD
is the external load capacitance on the pin. At
room temperature, the average R
PD
is approximately 40Ω.
With a 150pF load capacitance the reset line can pull down
in about 13ns.
Figure 5. Typical Transient Duration vs Overdrive
Required to Trip Comparator
RESET COMPARATOR OVERDRIVE (% OF V
RTX
)
0.1
250
TYPICAL TRANSIENT DURATION (µs)
300
350
400
1 10 100
29031 F05
200
150
50
0
100
RESET OCCURS
ABOVE CURVE
T
A
= 25°C
v$?.___ LIT $3.11 LT L7UHN§GB
13
LTC2903-1
29031f a
TYPICAL APPLICATIO S
U
V1
GND
V2
SYSTEM RESET
1V
(VTRIP = 0.884V)
1.8V
RST
V4
V3
3.3V
2.5V
1
2
3
6
5
4
LTC2903-A1
R2
100k
2903 TA02
C1
0.1µF
C2
0.1µF
R1
76.8k
Quad Supply Monitor with Adjustable Input
Fixed Quad Supply Monitor with LED Indication on RST
V1
GND
V2
SYSTEM RESET
1.8V
2.5V
RST
V4
V3
5V
3.3V
1
2
3
6
5
4
LTC2903-B1
LED
1k
5V
2903 TA05
C1
0.1µF
C2
0.1µF
.||- IIl-Iww $ II|»'w»< $="" l7="" ljfjw="">
14
LTC2903-1
29031f a
TYPICAL APPLICATIO S
U
Quad Supply Monitor with Unused Input Pulled Above Threshold
V1
GND
V2
SYSTEM RESET
–5.2V
RST
V4
V3
5V
3.3V
1
2
3
6
5
4
LTC2903-C1
2903 TA03
C1
0.1µF
C2
0.1µF
Quad Supply Monitor with 3 Adjustable Inputs Monitoring
5% Supplies
V1
GND
SYSTEM RESET
12V
(V
TRIP
= 11.25V)
2.5V
(V
TRIP
= 2.325V)
RST
V4
V2 V3
3.3V
1.8V
(V
TRIP
= 1.685V)
1
2
6
5
34
LTC2903-D1
100k
2903 TA06
C1
0.1µF2150k
100k100k
365k
237k
385MAX + u 20 950 f I DATUM ‘A ¢ I 9‘ L, u an 7 n 50 T ‘ ‘ NOTE I DIMENSIONS ARE W MILLIMETERS 2 DRAWING NOT TO SCALE 3 DIMENSIONS ARE INCLUSIVE 0F PLAN 4 DIMENSIONSARE EXCLUSIVE OF MOLD 5 MOLD FLASH SHALL NOT EXCEED u 25 5 JEDEC PACKAGE REFERENCE Is M049 L7UHN§GB
15
LTC2903-1
29031f a
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.30 – 0.45
6 PLCS (NOTE 3)
DATUM ‘A’
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302
2.90 BSC
(NOTE 4)
0.95 BSC
1.90 BSC
0.80 – 0.90
1.00 MAX 0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
PIN ONE ID
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
3.85 MAX
0.62
MAX
0.95
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
|| || § L7 LJFJW
16
LTC2903-1
29031f a
© LINEAR TECHNOLOGY CORPORATION 2003
LT/TP 1004 1K • PRINTED IN THE USA
PART NUMBER DESCRIPTION COMMENTS
LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65 Threshold
LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.9V Threshold
LTC699 5V Supply Monitor and Watchdog Timer 4.65 Threshold
LTC1232 5V Supply Monitor, Watchdog Timer and Pushbutton Reset 4.37V/4.62V Threshold
LTC1326 Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ 4.725V, 3.118V, 1V Thresholds (±0.75%)
LTC1326-2.5 Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%)
LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI t
FAIL
Timing Specifications
LTC1726-2.5 Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ Adjustable RESET and Watchdog Time Outs
LTC1726-5 Micropower Triple Supply Monitor for 5V, 3.3V and ADJ Adjustable RESET and Watchdog Time Outs
LTC1727-2.5/LTC1727-5 Micropower Triple Supply Monitors with Open-Drain Reset Individual Monitor Outputs in MSOP
LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitors with Open-Drain Reset 5-Lead SOT-23 Package
LTC1728-2.5/LTC1728-5 Micropower Triple Supply Monitors with Open-Drain Reset 5-Lead SOT-23 Package
LTC1985-1.8 Micropower Triple Supply Monitor with Push-Pull Reset Output 5-Lead SOT-23 Package
LTC2900 Quad Voltage Monitor in MSOP 16 User Selectable Combinations,
±1.5% Threshold Accuracy
LTC2901 Quad Voltage Monitor with Watchdog 16 User Selectable Combinations, Adjustable Timers
LTC2902 Quad Voltage Monitor with RST Disable 16 User Selectable Combinations, Adjustable Tolerance
LTC2904/LTC2905/ Precision Dual Supply Monitors Pin Selectable Thresholds
LTC2906/LTC2907
LTC2908 Precision Six Supply Monitor 8-Lead SOT-23 and DFN Packages
LTC2920-1/LTC2920-2 Single/Dual Power Supply Margining Controller <0.4% Margin Voltage Precision
LTC2921/LTC2922 Power Supply Trackers with Input Monitors 3 (LTC2921) and 5 (LTC2922) Remote Sense Switches
LTC2923 Power Supply Tracking Controller Tracks Up and Down, Supply Sequencing
RELATED PARTS
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
TYPICAL APPLICATIO
U
Quad Supply Monitor with Manual Reset Button
GND
V2
V4
V3
3.3V
2.5V
LTC2903-A1
RSTV1 SYSTEM RESET
1.8V
3.3V
R2
100k
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
R1
2050k
R3
10k
2903 TA04
C1
0.1µF
C2
0.1µF
R
ESD
*
10k
MANUAL
RESET BUTTON
(NORMALLY OPEN)
12V
(V
TRIP
= 10.75V)