MIC2937A, MIC29371, MIC29372 Datasheet by Microchip Technology

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EIIIIIREU
MIC2937A/29371/29372 Micrel, Inc.
May 2006 1 MIC2937A/29371/29372
Features
High output voltage accuracy
Guaranteed 750mA output
Low quiescent current
Low dropout voltage
Extremely tight load and line regulation
Very low temperature coefficient
Current and thermal limiting
Input can withstand –20V reverse battery and +60V posi-
tive transients
Error flag warns of output dropout
Logic-controlled electronic shutdown
Output programmable from 1.24V to 26V(MIC29372)
Available in TO-220, TO-263, TO-220-5, and TO-263-5
packages.
Applications
Battery Powered Equipment
Cellular Telephones
Laptop, Notebook, and Palmtop Computers
PCMCIA VCC and VPP Regulation/Switching
Bar Code Scanners
Automotive Electronics
SMPS Post-Regulator/ DC to DC Modules
High Efficiency Linear Power Supplies
Pin Configuration
GROUND OUTPUTINPUT
TO-220-5 Package
(MIC29371/29372BT/WT)
TO-220 Package
(MIC2937A-xxBT/WT)
General Description
The MIC2937A family are “bulletproof” efficient voltage regu-
lators with very low dropout voltage (typically 40mV at light
loads and 300mV at 500mA), and very low quiescent current
(160µA typical). The quiescent current of the MIC2937A in-
creases only slightly in dropout, thus prolonging battery life.
Key MIC2937A features include protection against reversed
battery, fold-back current limiting, and automotive “load dump”
protection (60V positive transient).
The MIC2937 is available in several configurations. The
MIC2937A-xx devices are three pin fixed voltage regulators
with 3.3V, 5V, and 12V outputs available. The MIC29371 is
a fixed regulator offering logic compatible ON/OFF switching
input and an error flag output. This flag may also be used as
a power-on reset signal. A logic-compatible shutdown input
is provided on the adjustable MIC29372, which enables the
regulator to be switched on and off.
TO-263 Package
(MIC2937A-xxBU/WU)
GROUND OUTPUTINPUT
TO-263-5 Package
(MIC29371/29372BU/WU)
Five Lead Package Pin Functions:
MIC29371 MIC29372
1) Error Adjust
2) Input Shutdown
3) Ground Ground
4) Output Input
5) Shutdown Output
The TAB is Ground on the TO-220 and TO-263 packages.
MIC2937A/29371/29372
750mA Low-Dropout Voltage Regulator
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
21 3
1 2 3 4 5
21 3
1 2 3 4 5
ng Information
MIC2937A/29371/29372 Micrel, Inc.
MIC2937A/29371/29372 2 May 2006
Ordering Information
Part Number Voltage Junction Temp. Range Package
Standard RoHS Compliant*
MIC2937A-3.3BU MIC2937A-3.3WU 3.3V –40ºC to +125ºC TO-263-3
MIC2937A-3.3BT MIC2937A-3.3WT 3.3V –40ºC to +125ºC TO-220-3
MIC2937A-5.0BU MIC2937A-5.0WU 5.0V –40ºC to +125ºC TO-263-3
MIC2937A-5.0BT MIC2937A-5.0WT 5.0V –40ºC to +125ºC TO-220-3
MIC2937A-12BU MIC2937A-12WU 12V –40ºC to +125ºC TO-263-3
MIC2937A-12BT MIC2937A-12WT 12V –40ºC to +125ºC TO-220-3
MIC29371-3.3BU MIC29371-3.3WU 3.3V –40ºC to +125ºC TO-263-5
MIC29371-3.3BT MIC29371-3.3WT 3.3V –40ºC to +125ºC TO-220-5
MIC29371-5.0BU MIC29371-5.0WU 5.0V –40ºC to +125ºC TO-263-5
MIC29371-5.0BT MIC29371-5.0WT 5.0V –40ºC to +125ºC TO-220-5
MIC29371-12BU MIC29371-12WU 12V –40ºC to +125ºC TO-263-5
MIC29371-12BT MIC29371-12WT 12V –40ºC to +125ºC TO-220-5
MIC29372BU MIC29372WU ADJ –40ºC to +125ºC TO-263-5
MIC29372BT MIC29372WT ADJ –40ºC to +125ºC TO-220-5
* RoHS compliant with ‘high-melting solder exemption.
w ( Symbol Parameter Conditions Min Typical Max Units —2 2 ‘l M‘CZQS7A712 and 29371712 only 71.5 1 5 —3 3 \l —4 4 AVD Ouipui Voiiage (Note 2) 20 100 ppm/”C AT 350 AvD Lme Reguiahon vN : v , +1v Io 26V 0.03 010 % vD 0.40 AVD Load Reguiahon \L: 510 SOOmA 0.04 0 16 % W Note 3 0.30 VN , V Dropoui Voiiage \L : SmA 80 150 mV 750 Ground Pm Curreni \L : SmA 160 250 0A ‘L Ground Pm VN : 0 5V less ihan designed V Y 200 500 0A Note 5 \D i , Curreni Lxmxi V ,:0V 1.1 15 A AVD Thermai Reguiahon (Note 7) 0.05 0 2 %/W APD e Ouipui Noise L :10pF 400 W RMS
MIC2937A/29371/29372 Micrel, Inc.
May 2006 3 MIC2937A/29371/29372
Electrical Characteristics
Limits in standard typeface are for TJ = 25°C and limits in boldface apply over the full operating temperature range. Unless other-
wise specified, VIN = VOUT + 1V, IL = 5mA, CL = 10µF. The MIC29372 are programmed for a 5V output voltage, and VSHUTDOWN ≤ 0.6V
(MIC29371-xx and MIC29372 only).
Symbol Parameter Conditions Min Typical Max Units
VO Output Voltage Variation from factory trimmed VOUT –1 1 %
Accuracy –2 2
5mAIL ≤ 500mA –2.5 2.5
MIC2937A-12 and 29371-12 only: –1.5 1.5
–3 3
5mA IL ≤ 500mA –4 4
ΔVO Output Voltage (Note 2) 20 100 ppm/°C
ΔT Temperature Coef. Output voltage > 10V 80 350
ΔVO Line Regulation VIN = VOUT + 1V to 26V 0.03 0.10 %
VO 0.40
ΔVO Load Regulation IL = 5 to 500mA 0.04 0.16 %
VO (Note 3) 0.30
VIN VO Dropout Voltage IL = 5mA 80 150 mV
(Note 4) 180
IL = 100mA 200
Output voltage > 10V 240
IL = 500mA 300
Output voltage > 10V 420
IL = 750mA 370 600
750
IGND Ground Pin Current IL = 5mA 160 250 µA
(Note 5) 300
IL = 100mA 1 2.5 mA
3
IL = 500mA 8 13
16
IL = 750mA 15 25
IGNDDO Ground Pin VIN = 0.5V less than designed VOUT 200 500 µA
Current at Dropout (VOUT ≥ 3.3V)
(Note 5) IO = 5mA
ILIMIT Current Limit VOUT = 0V 1.1 1.5 A
(Note 6) 2
ΔVO Thermal Regulation (Note 7) 0.05 0.2 %/W
ΔPD
en Output Noise CL = 10µF 400 µV RMS
Voltage
(10Hz to 100kHz) CL = 100µF 260
IL = 100mA
Absolute Maximum Ratings
Power Dissipation (Note 1)...............................................Internally Limited
Lead Temperature (Soldering, 5 seconds).........................................260°C
Storage Temperature Range.............................................–65°C to +150°C
Operating Junction Temperature Range ..........................–40°C to +125°C
TO-220 θJC .....................................................................................2.5°C/W
TO-263 θJC .....................................................................................2.5°C/W
Input Supply Voltage..............................................................–20V to +60V
Operating Input Supply Voltage..................................................2V to 26V
Adjust Input Voltage (Notes 9 and 10).................................–1.5V to +26V
Shutdown Input Voltage .......................................................–0.3V to +30V
Error Comparator Output Voltage.........................................–0.3V to +30V
Across the full operating temperature, the minimum input voltage range for
full output current is 4.3V to 26V. Output will remain in-regulation at lower
output voltages and low current loads down to an input of 2V at 25°C.
MIC2937A/29371/29372 Micrel, Inc.
MIC2937A/29371/29372 4 May 2006
Electrical Characteristics (Continued)
MIC29372
Parameter Conditions Min Typical Max Units
Reference Voltage 1.223 1.235 1.247 V
1.210 1.260 V max
Reference Voltage (Note 8) 1.204 1.266 V
Adjust Pin 20 40 nA
Bias Current 60
Reference Voltage (Note 7) 20 ppm/°C
Temperature
Coefficient
Adjust Pin Bias 0.1 nA/°C
Current Temperature
Coefficient
Error Comparator
Output Leakage VOH = 26V 0.01 1.00 µA
Current 2.00
Output Low VIN = 4.5V 150 250 mV
Voltage IOL = 250µA 400
Upper Threshold (Note 9) 40 60 mV
Voltage 25
Lower Threshold (Note 9) 75 95 mV
Voltage 140
Hysteresis (Note 9) 15 mV
Shutdown Input
Input Logic Voltage 1.3 V
Low (ON) 0.7
High (OFF) 2.0
Shutdown Pin VSHUTDOWN = 2.4V 30 50 µA
Input Current 100
VSHUTDOWN = 26V 450 600 µA
750
Regulator Output (Note 10) 3 10 µA
Current in Shutdown 20
MIC29371
MIC29371/MIC29372
FEEDEAC
MIC2937A/29371/29372 Micrel, Inc.
May 2006 5 MIC2937A/29371/29372
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not
apply when operating the device outside of its rated operating conditions. The maximum allowable power dissipation is a function of the
maximum junction temperature, TJ (MAX), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum
allowable power dissipation at any ambient temperature is calculated using: P(MAX) = (TJ(MAX) – TA) / θJA. Exceeding the maximum allowable
power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
Note 2: Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 3: Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to
heating effects are covered by the thermal regulation specification.
Note 4: Dropout Voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value
measured at 1V differential. At low values of programmed output voltage, the minimum input supply voltage of 4.3V over temperature must
be taken into account. The MIC2937A operates down to 2V of input at reduced output current at 25°C.
Note 5: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current
plus the ground pin current.
Note 6: The MIC2937A family features fold-back current limiting. The short circuit (VOUT = 0V) current limit is less than the maximum
current with normal output voltage.
Note 7: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, exclud-
ing load or line regulation effects. Specifications are for a 200mA load pulse at VIN = 20V (a 4W pulse) for T = 10ms.
Note 8: VREF ≤ VOUT ≤ (VIN – 1 V), 4.3V ≤ VIN ≤ 26V, 5mA < IL ≤ 750 mA, TJ ≤ TJ MAX.
Note 9: Comparator thresholds are expressed in terms of a voltage differential at the Adjust terminal below the nominal reference voltage
measured at 6V input (for a 5V regulator). To express these thresholds in terms of output voltage change, multiply by the error amplifier
gain = VOUT /VREF = (R1 + R2)/R2. For example, at a programmed output voltage of 5V, the Error output is guaranteed to go low when
the output drops by 95 mV x 5V/1.235 V = 384 mV. Thresholds remain constant as a percent of VOUT as VOUT is varied, with the dropout
warning occurring at typically 5% below nominal, 7.7% guaranteed.
Note 10: Circuit of Figure 3 with R1 ≥ 150kΩ. VSHUTDOWN ≥ 2V and VIN ≤ 26V,VOUT = 0.
Note 11: When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode
clamped to ground.
Note 12: Maximum positive supply voltage of 60V must be of limited duration (< 100ms) and duty cycle ( ≤ 1%). The maximum continu-
ous supply voltage is 26V.
FEEDBACK
SENSE
Q15A
OUT
Q24
Q26
R27
V TAP
R28
R18
20 k
Q25
Q23
Q22
R15
100 k
R16
30 k
Q29
Q28
R17
10
R21 8 Ω
R17
12 k
Q31
Q30
R23 60 k Ω
SHDN
R24
50 k
R22
150 k
Q21
Q19
C2
40 pF
R14
350
k Ω
Q14
R13
100
k Ω
Q18
R12
110
k Ω
Q20
Q9
Q15B
Q8
Q7
R11
20.6
k Ω
Q5
R8
31.4 k
R10
150
k Ω
R9
27.8 k
Q11
Q12
Q13
R6
140
k Ω
R5
180
k Ω
R4
13 k
R3
50 k
Q2
C1
20
pF
Q4
Q3
R11
18
k Ω
Q6
Q1
10
R1
20 k
R2
50 k
Q41
R30
30
k Ω
Q40
Q34
GND
Q36
Q37
R25
2.8 k
Q38
ERROR
R26
60 k
Q39
Q42
Q16
Q17
50 k
10 k
IN
DENOTES CONNECTION ON
MIC2937A-xx AND MIC29371-xx
VERSIONS ONLY
Schematic Diagram
GROUND CURRENT (mA) OUTPUT VOLTAGE (v) Dropout Voltage Dropout Voltage F‘XED 5v VERSION F‘XED 5v Dropout \XED 5v 20 JD 0 m 20 \NPUT VOLTAGE (v)
MIC2937A/29371/29372 Micrel, Inc.
MIC2937A/29371/29372 6 May 2006
Typical Characteristics
0
100
200
300
400
500
0 200 400 600 800
)V
m(
EGATLOV
T
UO
PO
RD
OUTPUT CURRENT (mA)
Dropout Voltage
vs. Output Current
0
100
200
300
400
500
600
700
-60 -30 0 30 60 90 120 150
)Vm
(
EGAT
L
OVTUOPORD
TEMPERATURE (°C)
Dropout Voltage
vs. Temperature
LOAD
0
1
2
3
4
5
6
0 1 2 3 4 5 6
)
V
(
EGATLO
V
TUPTUO
INPUT VOLTAGE (V)
Dropout
Characteristics
I
LOAD
= 5mA
I
LOAD
= 750mA
0.1
1
10
30
1 10 100 1000
)A
m
(TNERRU
CDN
UORG
OUTPUT CURRENT (mA)
Ground Current
vs. Output Current
0
50
100
150
200
012345678
(TN
E
RR
UCDN
UORG µ )
A
SUPPLY VOLTAGE (V)
Ground Current
vs. Supply Voltage
FIXED 5V VERSION
I
LOAD = 5mA
0
5
10
15
20
25
30
0 2 4 6 8 10
)Am(TNERRUCDNUORG
INPUT VOLTAGE (V)
Ground Current
vs. Supply Voltage
FIXED 5V
I
LOAD = 750mA
0.00
0.05
0.10
0.15
0.20
0.25
-60 -30 0 30 60 90 120 150
)Am(T
N
ERRUCDN
UO
RG
TEMPERATURE (°C)
Ground Current
vs. Temperature
I
LOAD
= 5mA
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
-60 -30 0 30 60 90 120 150
)
A
m
(T
N
ER
R
UC
DNUO
R
G
TEMPERATURE (°C)
Ground Current
vs. Temperature
LOAD
0
5
10
15
20
25
30
-60 -30 0 30 60 90 120 150
)A
m(T
NE
R
R
U
CD
N
UO
RG
TEMPERATURE (°C)
Ground Current
vs. Temperature
LOAD
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
-60 -30 0 30 60 90 120 150
)
A(T
NE
R
R
UC
TEMPERATURE (°C)
Short Circuit and Maximum
Current vs. Temperature
V
OUT
= V
NOMINAL
0.5V
V
OUT
= 0V
FIXED 5V
VERSION
-100
0
100
200
300
400
500
-30 -20 -10 0 10 20 30
(
TNERRUCDNUORG µ )A
INPUT VOLTAGE (V)
Ground Current
vs. Input Voltage
R
LOAD
= 100
3.20
3.22
3.24
3.26
3.28
3.30
3.32
3.34
3.36
3.38
3.40
-60 -30 0 30 60 90 120 150
)V(EGA
T
LOVTUPTU
O
TEMPERATURE (°C)
Fixed 3.3V Output Voltage
vs. Temperature
ENABLE CURRENT (VA) MI629371/Z Shmdown Currem \ VrV \\ v:2v FREQUENCY (Hz 100x10 >
MIC2937A/29371/29372 Micrel, Inc.
May 2006 7 MIC2937A/29371/29372
0
25
50
75
100
125
-60 -30 0 30 60 90 120 150
(
TNE
R
R
UC
ELBANE µ )
A
TEMPERATURE (°C)
MIC29371/2 Shutdown Current
vs. Temperaure
V
EN
= 5V
V
EN
= 2V
-300
-150
0
150
300
∆ )Vm(TUPTUO
-250
0
250
500
750
1000
-5 0 5 10
)Am(TUPTUO
TIME (ms)
Load Transient
C
OUT
= 10
µ
F
5mA
-200
-100
0
100
200
∆ )Vm(TUPTUO
-250
0
250
500
750
1000
-5 0 5 10
)Am(TUPTUO
TIME (ms)
Load Transeint
OUT
µ
5mA
0
10
20
30
40
50
-60 -30 0 30 60 90 120 150
)An(
T
N
ER
RUCN
I
PTSUJDA
TEMPERATURE (°C)
MIC29372/3 Adjust Pin
Current vs. Temperature
I
LOAD
= 1mA
-40
-20
0
20
40
∆ )
V
m(T
U
PTUO
4
6
8
10
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
)V(TUP
N
I
TIME (ms)
Line Transient
C
OUT
= 10
µ
F
IL = 5mA
-10
0
10
20
∆ )
V
m(T
U
PTU
O
4
6
8
10
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
)V(
TUPN
I
TIME (ms)
Line Transient
OUT
µ
IL = 5mA
0.01
0.1
1
10
01
x1 0
01
x01 0
01x001 0
01
x1 3
01x01 3
01
x001 3
01x1 6
(ECN
AD
EP
MI
TU
P
TU
O)
FREQUENCY (Hz)
Output Impedance
vs. Frequency
I
LOAD
= 10mA
gram dep ERROR t voltage fl ERROR ERROR * ERROR
MIC2937A/29371/29372 Micrel, Inc.
MIC2937A/29371/29372 8 May 2006
Applications Information
External Capacitors
A 10µF (or greater) capacitor is required between the MIC2937A
output and ground to prevent oscillations due to instability. Most
types of tantalum or aluminum electrolytics will be adequate;
film types will work, but are costly and therefore not recom-
mended. Many aluminum electrolytics have electrolytes that
freeze at about –30°C, so solid tantalums are recommended
for operation below –25°C. The important parameters of the
capacitor are an effective series resistance of about or
less and a resonant frequency above 500kHz. The value of
this capacitor may be increased without limit.
At lower values of output current, less output capacitance is
required for output stability. The capacitor can be reduced to
0.5µF for current below 10mA or 0.15µF for currents below
1 mA. Adjusting the MIC29372 to voltages below 5V runs the
error amplifier at lower gains so that more output capacitance
is needed. For the worst-case situation of a 750mA load at
1.23V output (Output shorted to Adjust) a 22µF (or greater)
capacitor should be used.
The MIC2937A/29371 will remain in regulation with a minimum
load of 5mA. When setting the output voltage of the MIC29372
version with external resistors, the current through these resis-
tors may be included as a portion of the minimum load.
A 0.1µF capacitor should be placed from the input to ground
if there is more than 10 inches of wire between the input and
the AC filter capacitor or if a battery is used as the input.
Error Detection Comparator Output (MIC29371)
A logic low output will be produced by the comparator when-
ever the MIC29371 output falls out of regulation by more than
approximately 5%. This figure is the comparator’s built-in
offset of about 75mV divided by the 1.235V reference volt-
age. (Refer to the block diagram on Page 1). This trip level
remains “5% below normal” regardless of the programmed
output voltage of the MIC29371. For example, the error flag
trip level is typically 4.75V for a 5V output or 11.4V for a 12V
output. The out of regulation condition may be due either to
low input voltage,extremely high input voltage, current limit-
ing, or thermal limiting.
Figure 1 is a timing diagram depicting the ERROR signal
and the regulated output voltage as the MIC29371 input is
ramped up and down. The ERROR signal becomes valid (low)
at about 1.3V input. It goes high at about 5V input (the input
voltage at which VOUT = 4.75). Since the MIC29371’s dropout
voltage is load-dependent (see curve in Typical Performance
Characteristics), the input voltage trip point (about 5V) will
vary with the load current. The output voltage trip point (ap-
proximately 4.75V) does not vary with load.
* SEE APPLICATIONS INFORMATION
Figure 1. ERROR Output Timing
The error comparator has an NPN open-collector output which
requires an external pull-up resistor. Depending on system
requirements, this resistor may be returned to the 5V output
or some other supply voltage. In determining a value for this
resistor, note that while the output is rated to sink 250µA, this
sink current adds to battery drain in a low battery condition.
Suggested values range from 100k to 1MΩ. The resistor is
not required if this output is unused.
Programming the Output Voltage (MIC29372)
The MIC29372 may programmed for any output voltage be-
tween its 1.235V reference and its 26V maximum rating. An
external pair of resistors is required, as shown in Figure 3.
The complete equation for the output voltage is
VOUT = VREF x { 1 + R1/R2 } – |IFB| R1
where VREF is the nominal 1.235 reference voltage and IFB is
the Adjust pin bias current, nominally 20nA. The minimum rec-
ommended load current of 1µA forces an upper limit of 1.2MΩ
on the value of R2, if the regulator must work with no load (a
condition often found in CMOS in standby), IFB will produce
a –2% typical error in VOUT which may be eliminated at room
temperature by trimming R1. For better accuracy, choosing
R2 = 100k reduces this error to 0.17% while increasing the
resistor program current to 12µA. Since the MIC29372 typically
draws 100µA at no load with SHUTDOWN open-circuited,
this is a negligible addition.
Reducing Output Noise
In reference applications it may be advantageous to reduce
the AC noise present at the output. One method is to reduce
the regulator bandwidth by increasing the size of the output
capacitor. This is relatively inefficient, as increasing the capaci-
tor from 1µF to 220µF only decreases the noise from 430µV
to 160µVRMS for a 100kHz bandwidth at 5V output. Noise can
be reduced by a factor of four with the adjustable regulators
*
*
OUTPUT
VOLTAGE
INPUT
VOLTAGE
ERROR NOT
VALID
NOT
VALID
5V
1.3V
4.75V
“>7 UT H g m Dulgul n 3 av ‘ 5 av
MIC2937A/29371/29372 Micrel, Inc.
May 2006 9 MIC2937A/29371/29372
Automotive Applications
The MIC2937A is ideally suited for automotive applications
for a variety of reasons. It will operate over a wide range of
input voltages with very low dropout voltages (40mV at light
loads), and very low quiescent currents (100µA typical). These
features are necessary for use in battery powered systems,
such as automobiles. It is a “bulletproof” device with the abil-
ity to survive both reverse battery (negative transients up to
20V below ground), and load dump (positive transients up to
60V) conditions. A wide operating temperature range with low
temperature coefficients is yet another reason to use these
versatile regulators in automotive designs.
Figure 2. MIC2937A-5.0 Fixed +5V Regulator Figure 3. MIC29372 Adjustable Regulator
Typical Applications
Figure 5. MIC29372 5.0V or 3.3V Selectable Regulator with
Shutdown.
Figure 4. MIC29372 Wide Input Voltage Range Current Limiter
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
SHUTDOWN PIN LOW= ENABLE OUTPUT. Q1 ON = 3.3V, Q1 OFF = 5.0V.
C
BYPASS
1
2 R
1
• 200 Hz
π
with a bypass capacitor across R1, since it reduces the high
frequency gain from 4 to unity. Pick
or about 0.01µF. When doing this, the output capacitor must
be increased to 10µF to maintain stability. These changes
reduce the output noise from 430µV to 100µVRMS for a 100
kHz bandwidth at 5V output. With the bypass capacitor added,
noise no longer scales with output voltage so that improve-
ments are more dramatic at higher output voltages.
GND
+VIN
OUT
V
V
10µF
+
IN
V
OUT = 5V
IN
OUT
GND ADJUST
SHUTDOWN
V
V
SHUTDOWN
INPUT
OUT
V
1.2V 26V
1
R .01
µF
10µF
2
R
1.23V
REF
V
VOUT = VREF x (1 + )
1
R
2
R
OFF
ON
OUT
GND ADJUST
V
VIN
+VIN
VOUT VIN
SHUTDOWN
V
GND
OUT
+VIN
ADJUST
SHUTDOWN
INPUT
100pF
2N2222
1%
300k Ω
+5V to +7V
1%
180k Ω
+
10µF
470 k
OFF
ON
5V
3.3V
220k Ω
1%
VCC OUT
Input Output
0 3.3V
1 5.0V
‘ A > 04 ‘ V F 1 T I » 2L mm m \ 1‘ pr: Mm «1N m m c A um 434:1 «:97 D __ A1 A] UUUC EUUU U303 I O bl HD47 D053 “94 1345 , 92 51 we Dun; can: um 63 H 031:) D623 1466:) 138/: auym \J/ ‘ J1 man man 2232 am L1 0090 Dm— 2206 E794 00‘ K HMS DUES H43 1397 L 11 1135: u3e1 5915 9193 K 1 E 0400 nos: 10160 10668 0' 1 e was um 2:13 ass? 1 4 r 004 no“ 114 13 4L am. Plans '1 2 3 U] 3‘ ID' 3‘ ID' , o7 1~ 7' 1- 7- T03 WEW S1DE v1;w 1 113 u- 11 u- a- 04 w 22‘ 111‘ 22~ 11 was a 1 139/ was u nae - sane w v nan: ms Re: NOTE: FOOT ,ENGTH USWG GAL ”LANE MET—10D MEASJRE . T 0010". M Yep v1.3.1 1m v1“ up 1 “L4 a O 1 pm: 7 V A b 121 E1 0 E” M L 1: 1 i C1 .7 L 1, n, 7 1 A \«o :1 w w 15m 11 5 mm mm wgawyims 0 1n'
MIC2937A/29371/29372 Micrel, Inc.
MIC2937A/29371/29372 10 May 2006
Package Information
3-Pin TO-263 (U)
3-Pin TO-220 (T)
¥ 4 ¥ MM V m MAX 1 J 4319 4597 CA OA I Ru. 4. u. a. TCP V‘EW S‘DE V‘EW 1 mus Rec 77/.7 REC Lam Re: u254 REP ACTE ‘ PACKAGE UUTUNE ExcEUWE 0F MOLD mm a MmE EURR 2 PACKAGE OLTUNE \NCLVSWE or wao TH‘CKNESS 3 FOOT LENGTH MEASJREJ n \NTERCPT Pew BETWEEN 2mm A & LEAD smmE A PACKAGE mp MARK w EE m mp CENTER an LOWE: EErr 00>:wa M -c- S‘DE V‘EW Z BOWOM V‘EW m W m V \ u n / V V H1 . m U L Cl J1 V 2 7. l 3 4 E- » in DFSB RrF ” E‘ L ‘ ‘ D 48s New Nae For)! Lerng usmg gauge was ns'Jvufl wwwgmu uum'
MIC2937A/29371/29372 Micrel, Inc.
May 2006 11 MIC2937A/29371/29372
1
θ
θ1
3
θ
4θ
1
θ
2
θ
3
θ
4θ
2θ
1θ
5-Pin TO-263 (U)
5-Pin TO-220 (T)
MIC2937A/29371/29372 Micrel, Inc.
MIC2937A/29371/29372 12 May 2006
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 1999 Micrel, Inc.

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