ZXLD381 Datasheet by Diodes Incorporated

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Product Line (:1 MIX IncoRPonA'rEn SOT23-3 V“ E I] Gm, VME l/I IV ({
ZXLD381
ZXLD381
Document number: DS32188 Rev. 3 - 2
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SINGLE OR MULTI CELL LED DRIVER SOLUTION
Summary
The ZXLD381 is a single cell LED driver designed for applications where step-up voltage conversion from a very low input
voltage is required. These applications mainly operate from 1.5V or 1.2V cells. The IC generates constant current pulses that
are ideal for driving single or multiple LEDs over a wide range of operating voltages.
The ZXLD381 uses a PFM control technique to drive an internal switching transistor which a low saturation resistance. This
ensures high efficiency, even for input voltages as low as 1V.
The IC can start up under full load and operates down to an input voltage of only 0.9V.
The ZXLD381 is offered in the space saving SOT23 package or in die form, offering an excellent cost vs performance solution
for single cell LED driving applications.
Features
85% Efficiency
User adjustable output current
Single cell operation (0.9V minimum)
Low saturation voltage switching transistor
SOT23-3 package
Available also in Die form
Simple Application circuit
Application
LED flashlights and torches
LED backlights
White LED driver
Pin Assignments
SOT23-3
(Top View)
Typical Application Circuit
L1
LED
ZXLD381
GND
V
OUT
V
CC
V
IN
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ZXLD381
ZXLD381
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Block Diagram
Fig 1. ZXLD381 Block Diagram
Pin Description
Pin No. Name Description
1 GND Ground
2 VOUT Switch output external inductor/LED
3 VCC Supply voltage, generally Alkaline, NiMH or NiCd single cell
ZXLD381
GN D
VOUT
VC C L1
1.5V
LED
Cof fCon
Pulse
Control
Rsense
ZH'EX ® Insonnonnrsn
ZXLD381
ZXLD381
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Absolute Maximum Ratings
Parameter Rating Unit
Supply Voltage (VCC) -0.6 to 10 V
Output Voltage (VOUT) -0.6 to 20 V
Supply Current 20 mA
Output Switch Current 800 mA
Power Dissipation SOT23-3 450 mW
Power Dissipation Die 1 W
Operating Temperature Range 0 to 85 °C
Storage Temperature Range -55 to 150 °C
Electrical Characteristics Measured at TAMB = 25°C, L = 4.7µH and VCC = 1.5V unless otherwise specified.
Parameter Conditions Limits Units
Min Typ. Max
Supply Voltage Operating Range L = 10μH 0.9 2.2 V
Minimum Supply Start-up Voltage L = 10μH 0.8 0.9 V
Switch Current At turn-off 250 320 400 mA
Switch Saturation Voltage IOUT = 200mA 100 300 mV
Switch Leakage Current VOUT = 20V 40 70 120 µA
Mean LED Current VLED = 3.5V 40 55 70 mA
Efficiency VLED = 3.5V 85 %
Operating Frequency VLED = 3.5V 350 kHz
Discharge Pulse Width 0.7 1.5 2.5 µs
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ZXLD381
ZXLD381
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Device Description
The ZXLD381 is a simple PFM, DC-DC controller combined with a high performance internal switching transistor, enabling the
production of a high efficiency boost converter for use in single cell applications. A block diagram is shown for the ZXLD381 in
Fig 1.
When power is applied, an oscillator within the pulse control block forces the internal switching transistor to switch on to start
an energy charge cycle. The low saturation voltage switch pulls the VOUT pin close to ground which forces the supply voltage
across the external inductor L1. This causes a current to build up, storing energy in the inductor. During this phase, switch
current and supply voltage are monitored and used by the pulse control circuit to determine the optimum drive conditions and
on-time. At the end of the energy charge cycle, the internal switch is turned off rapidly, interrupting the current flow through L1
which causes the voltage on VOUT to rise dramatically. When the voltage on VOUT reaches the load LED's forward (on)
voltage, the inductor current is transferred from the internal switch to the LED, starting the energy discharge cycle. With the
voltage across the inductor reversed, the current flowing through it (and the LED) now falls. When the inductor current reaches
zero, the voltage on the VOUT pin falls back towards VCC. This action is sensed by the pulse control circuit, which initiates the
next energy charge cycle. Except for low level losses, all the energy stored in the inductor during a charge cycle will be
channeled to the load LED during the following discharge cycle.
The current fed into the load LED has a sawtooth waveform, the average (DC) value of which is kept constant by the pulse
control circuit for varying supply voltage and temperature. It is possible to change the output current given by the ZXLD381 by
changing the value of inductor L1. The larger the inductance of L1, the lower the output current. A table/graph showing the
relationship between inductance and output current is given later in this datasheet. Since the output current of the ZXLD381 is
a sawtooth waveform, its peak value is substantially larger than the DC/average value. The table also provides this data.
The internal switching transistor has a minimum collector-emitter breakdown voltage of 20V and this sets the maximum load
voltage allowable. The minimum value is set by a feature of the pulse control circuit that requires the load voltage to be at least
0.8V greater than VCC. (The device will function with load voltages smaller than this but output current regulation will be
impaired.) Higher than nominal load voltages will lower the average (DC) output current generated for a given inductor value.
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ZXLD381
ZXLD381
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Typical Characteristics
0
10
20
30
40
50
60
70
80
90
100
0.8 11.2
1.4 1.6 1.8 2
2.2µH
3.3µH
4.7µH
6.8µH
10µH
15µH
22µH
47µH
I (mA)
OUT
V (V)
I vs. V for L = 2.2µH to 47µH
CC
OUT(AVERAGE) CC
0
10
20
30
40
50
60
70
80
90
100
0.8 1 1.2 1.4 1.6 1.8 2
22µH
3.3µH
4.7µH
6.8µH
10µH
15µH
2.2µH
Efficiency (%)
V (V)
Efficiency vs. V for L = 2.2µH to 47µH
CC
CC
47µH
0
50
100
150
200
250
300
350
0.8 1 1.2 1.4 1.6 1.8 2
V (V)
I vs. V for L = 2.H to 4H
CC
IN CC
I (mA)
IN
2.2µH
3.3µH
4.7µH
6.8µH
10µH
15µH
22µH
47µH
Channel-1 (Upper): I @ 100mA/cm
Channel-2 (Lower): V @ 1V/cm
Timebase: 500ns/cm
Operating Waveforms for L = 4.7µH, V = 1.5V
LED
OUT
CC
Notes: VLED = 3.5V for all graphs
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ZXLD381
ZXLD381
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Typical Characteristics (Cont.)
0
50
100
150
200
250
300
350
400
450
0.8 1 1.2 1.4 1.6 1.8 2
V (V)
f vs. V for L = 47µH
CC
OSC CC
f (kHz)
OSC
Notes: VLED = 3.5V for all graphs
Insonnonnrsn Product Line at ZH'EX L ILED(peak) ILED(avg) luH) (mm mm vac L1 47 35 6.5 22 80 15 —.— ‘s. zxww vour 15 120 20 10 190 30 Z E LED 6.8 260 45 N: 4.7 380 55 3.3 510 67 2.2 640 76 '- ILED (uH) (mA) vcc Ll 47 5 _ D‘ 22 13.5 - m: zxum‘ vour W 15 18 SZ E LED 10 27 6.8 41 MD 4.7 50 3.3 61 2.2 69
ZXLD381
ZXLD381
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Application Examples
Standard Operating Mode
Notes: VLED = 3.5V
Low Ripple LED Current Mode
Notes: VLED = 3.5V, D1 = ZHCS1000, C1 = 1F (low ESR)
roduct Line 01 ‘15,” m5® IncoRPoRATEn
ZXLD381
ZXLD381
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Ordering Information
Part Number Package Part Mark Tape Width
(mm) Quantity
(per reel)
ZXLD381FHTA SOT23 381 8 3000
Package Outline Dimensions
Dim. Millimeters Inches Dim. Millimeters Inches
Min. Max. Min. Max. Min. Max. Min. Max.
A - 1.12 - 0.044 e1 1.90 NOM 0.075 NOM
A1 0.01 0.10 0.0004 0.004 E 2.10 2.64 0.083 0.104
b 0.30 0.50 0.012 0.020 E1 1.20 1.40 0.047 0.055
c 0.085 0.20 0.003 0.008 L 0.25 0.60 0.0098 0.0236
D 2.80 3.04 0.110 0.120 L1 0.45 0.62 0.018 0.024
e 0.95 NOM 0.037 NOM - - - - -
E
e
L
e1
D
A
c
E1
L1
A1
b
3leads
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ZXLD381
ZXLD381
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IMPORTANT NOTICE
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes
without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or
trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume
all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated
website, harmless against all damages.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
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indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.
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LIFE SUPPORT
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
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use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
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