ZETEX ZXLD383

A Product Line of
Diodes Incorporated
ZXLD383
Single or multi cell LED driver with enable/rectifier input for solar
charged lamp applications
Description
Summary
The ZXLD383 is a single or multi cell LED
driver designed for applications requiring
step-up voltage conversion from a very low
input voltage. The IC generates constant
current pulses that are ideal for driving single
or multiple LEDs over a wide range of
operating voltages. It includes an on/off
enable input that can be driven directly from
a photocell array or an open collector/drain
logic output. The enable input features an
ultra-low voltage drop diode to ground,
eliminating the need for a photocell array
isolation diode in Garden Light applications.
The ZXLD383 uses a PFM control technique to
drive an internal switching transistor which
exhibits a low saturation resistance. This
ensures high efficiency, even for input voltages
as low as 1.0V.
Features
Applications
•
85% efficiency
•
Garden lights
•
User adjustable output current
•
Door/pathway illumination
•
Single cell operation
•
LED flashlight and torches
•
Low saturation voltage
•
LED backlights
•
TSOT23-5 package
•
White LED driver
•
Available also in die form
•
Gated boost supply generator
•
Simple application circuit
The IC can start up under full load and operates
down to an input voltage of below 0.9V.
The ZXLD383 is offered in the space saving
TSOT23-5 package or in die form, offering an
excellent cost vs performance solution for
single cell LED driving applications.
Z XLD 383
EN A
5
1
VC C
D iode A rray
GN D
NC
L1
2
3
4
VOU T
N I MH
1. 2V
LE D
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ZXLD383
Absolute maximum ratings
Supply Voltage (Vcc)
Output Voltage (Vout)
Enable Voltage (Vena)
Supply Current
Output Switch Current
Power Dissipation (TSOT23-5)
Power Dissipation Die
Operating Temperature Range
Storage Temperature Range
-0.6V to 6V
-0.6V to 20V
-1V to 3.5V
20mA
800mA
450mW
1W
-20°C to +85°C
-55°C to +150°C
Electrical Characteristics
Measured at TAMB = 25°C, L = 6.8uH, IENA = 0 and VCC = 1.5V unless otherwise specified.
Parameter
Conditions
Supply Voltage
Operating Range
Minimum Supply
Start-up Voltage
Supply Current
Quiescent
Supply Current
Shutdown
Supply Current
Under-Voltage
L = 10uH
Switch Current
Switch Saturation
Voltage
Switch Leakage
Current
Mean LED Current
Efficiency
At turn-off
IOUT = 200mA
Operating
Frequency
Discharge Pulse
Width
VLED = 3.5V
Enable Input
Threshold
Enable Input
Current
Enable Input
Voltage
L = 10uH
2
VENA = VCC – 0.8V
Limits
Typ
250
V
0.8
0.9
V
4
8
mA
17
30
uA
20
uA
400
300
mA
mV
10
uA
65
mA
%
320
100
VOUT = 20V, VENA = 0V
VLED = 3.5V
VLED = 3.5V
40
Units
Max
3.3
VCC = 0.6V
50
85
330
kHz
0.7
1.5
2.5
us
VCC -
VCC -
VCC -
V
VENA = 0.2V
0.8
0
0.6
-11
0.2
-20
uA
IENA = -20mA
0
-90
-250
mV
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Min
0.9
2
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ZXLD383
Typical characteristics
ZX L D383 Efficie n cy vs V C C
ZX L D383 I O U T(AV E R AG E ) vs V C C
90
100
80
90
80
70
70
4.7uH
Efficien cy (% )
I OU T (m A )
60
6.8uH
50
10uH
40
22uH
4.7uH
60
6.8uH
10uH
50
22uH
40
47uH
47uH
30
30
20
20
10
10
0
0
0.8
1
1.2
1.4
1.6
1.8
0.8
2
1
1.2
1.4
1.6
1.8
2
V C C (V )
V C C (V )
ZX L D383 I IN vs V C C
ZX LD383 P e a k_I IN vs V C C
250
500
450
200
400
350
4.7uH
150
4.7uH
300
I IN ( m A )
I IN ( m A )
6.8uH
10uH
22uH
100
6.8uH
250
10uH
22uH
200
47uH
47uH
150
50
100
50
0
0
0.8
1
1.2
1.4
1.6
1.8
2
0.8
V C C (V )
1
1.2
1.4
1.6
1.8
2
V C C (V )
ZX LD383 V ( E N A) vs I E N A
For V CC = 0.8, 1.0, 1.2 a nd 1.4V
Z X L D 38 3 O p era tin g W a vefo rm s fo r L = 6.8u H , V C C = 1.5V
450
400
350
V E NA (m V)
300
0.8V
250
1.0V
200
1.2V
1.4V
150
100
50
Channel -1 (Upper): I [email protected] 100mA/cm
Channel -2 (Lower): [email protected] 1V/cm
Timebase: 500ns/cm
0
0
10
20
30
40
50
IV E N A (m A )
Note VLED = 3.5V for all graphs
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ZXLD383
Device description
The ZXLD383 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. It includes a dual function Enable input which serves both as an operation
inhibit control and an ultra-low voltage drop isolation diode for battery charging purposes in
Garden Light applications. A block diagram is shown for the ZXLD383 in Figure 1.
VC C
L1
Z XLD 383
D iode A rray
VOU T
EN A
P uls e
C ont rol
N I MH
1. 2V
LE D
Dch
C on
Cof f
R s ens e
GN D
Figure 1 - ZXLD383 block diagram
With power applied and the enable pin held at VCC, 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 and is
combined with the output of an off-period timer to initiate the next energy charge cycle. Except
for low level losses, all the energy stored in the inductor during a charge cycle is channelled 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 ZXLD383 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
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ZXLD383
output current of the ZXLD383 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 0.5V 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.
The Enable pin inhibits the operation of the output switch if held at a potential of Vcc-0.8V or
lower. It also includes a diode to ground which allows the input to be wired directly to a photocell
array that will then both enable operation of the converter when in darkness and charge the IC’s
power source in daylight conditions. The diode function is performed by an active circuit that
gives an ultra low forward voltage drop (typically less than 0.1V at 20mA). This allows the use of
a lower output voltage photocell array (lower cost) without degrading performance.
Application Examples
Apart from the Garden Light application circuit shown on the front page of this datasheet, the
ZXLD383 may be used in many other ways. The following circuits and notes show some other
possibilities and give typical performance details.
Standard operating mode
The following circuit demonstrates how few components are required to produce a light source
using the ZXLD383. Operating from a single cell, this simple circuit is suited for use in car key
fobs, novelty products etc. where small size and low cost are critical aspects.
By directly wiring the Ena pin to Vcc, the part is permanently enabled once a power supply is
provided. The ZXLD383 is highly tolerant of supply ripple so no decoupling of Vcc should be
needed in a compactly constructed circuit. Also, the part’s capability of operating with a Vcc
below 0.9V means that this simple circuit will make the best use of available battery capacity.
The attached table shows the average LED currents that can be obtained using a range of inductor
values. Also shown are the peak currents required to achieve the given currents.
Z XLD 383
EN A
GN D
NC
1
5
I LE D (peak )
I LE D (avg)
(uH )
(m A )
(m A )
L1
2
3
L
VC C
4
VOU T
1. 5V
LE D
47
45
8.5
22
100
17.3
10
210
34
6.8
330
50
4.7
415
63
Note VLED = 3.5V
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ZXLD383
Low ripple LED current mode
It is possible that the peak LED current required to achieve a given average current is either too
high for the LED of choice or it leads to some loss of efficiency (due to LED resistance losses). In
these cases, just two extra low cost components can be added to provide a low ripple current
supply for the LED. The Schottky diode D1 and capacitor C1 rectifies and smoothes the output of
the ZXLD383 giving a low ripple current supply to the load LED. Of course, this circuit could also
be used to power loads other than LEDs.
Z XLD 383
EN A
GN D
1
5
VC C
L1
2
D1
NC
4
3
VOU T
C1
1. 5V
LE D
L
I LE D
(uH )
(m A )
47
7.5
22
15.5
10
31
6.8
46
4.7
58
Note: VLED =3.5V, D1=ZHCS1000, C1 = 1uF (low ESR)
Buck-boost mode
Simple boost converters can run into problems when the input supply voltage is similar to or
exceeds the intended load voltage as there is usually a direct current path from the power source
through to the load via the boost inductor. This path does not require switching action and so is
uncontrolled. When using the ZXLD383, this problem can be avoided by wiring the cathode of the
load LED to Vcc rather than ground. Without switching action, the LED is reverse-biased and so
no current can flow. When switching, the anode of the LED is driven to Vcc + Vf(led). The higher
than normal output voltage reduces the available output current as described earlier and this is
shown in the typical data provided.
LE D
Z XLD 383
3V
EN A
GN D
NC
1
5
VC C
L1
2
3
4
L
ILE D
(uH )
(m A )
47
5.5
22
10.3
10
23.2
6.8
36.7
4.7
46.2
VOU T
Note: VLED =3.5V
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ZXLD383
Low ripple buck-boost mode
The output of the Buck-Boost converter can be rectified and smoothed as with the standard circuit
to give a low ripple output to improve LED efficiency or to give a DC output for other loads.
C1
LE D
Z XLD 383
3V
EN A
GN D
1
5
VC C
L1
2
L
ILE D
(uH )
(m A )
47
5
22
9.7
10
21.7
6.8
34
4.7
43
D1
NC
3
4
VOU T
Note: VLED =3.5V, D1=ZHCS1000, C1 = 1uF (low ESR)
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ZXLD383
Pin descriptions
Pin No.
1
2
3
4
5
Name
ENA
GND
NC
VOUT
VCC
Description
Enable / Photodiode array battery charge input
Ground
Not connected (internally open circuit)
Switch output external inductor/LED
Supply voltage, generally Alkaline, NiMH or NiCd single cell
Pinout diagram
ZXLD383
ENA 1
5
VCC
4
VOUT
GND 2
NC 3
TSOT23-5
Top view
Ordering information
Device
Reel size
(inches)
Reel width
(mm)
Quantity per reel
Device mark
7”
8
3,000
383
ZXLD383ET5TA
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ZXLD383
Packaging information - TSOT23-5
Dim.
Millimeters
Inches
Dim.
Millimeters
Min.
Max.
Inches
Min.
Max.
Min.
Max.
Min.
Max.
A
-
1.00
-
0.0393
E1
1.60 BSC
0.062 BSC
A1
0.01
0.10
0.0003
0.0039
e
0.95 BSC
0.037 BSC
A2
0.84
0.90
0.0330
0.0354
e1
1.90 BSC
0.074 BSC
b
0.30
0.45
0.0118
0.0177
L
C
0.12
0.20
0.0047
0.0078
L2
D
2.90 BSC
0.114 BSC
E
2.80 BSC
0.110 BSC
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Q
9
0.10
0.60
0.25 BSC
4o
12o
0.0039
0.0236
0.010 BSC
4o
12o
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ZXLD383
Definitions
Product change
Diodes Incorporated reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or
service. Customers are solely responsible for obtaining the latest relevant information before placing orders.
Applications disclaimer
The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for
the user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is
assumed by Diodes Inc. with respect to the accuracy or use of such information, or infringement of patents or other intellectual property
rights arising from such use or otherwise. Diodes Inc. does not assume any legal responsibility or will not be held legally liable (whether
in contract, tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business,
contract, opportunity or consequential loss in the use of these circuit applications, under any circumstances.
Life support
Diodes Zetex 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
labelling 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.
Reproduction
The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the
company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a
representation relating to the products or services concerned.
Terms and Conditions
All products are sold subjects to Diodes Inc. terms and conditions of sale, and this disclaimer (save in the event of a conflict between the
two when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement.
For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Diodes sales office.
Quality of product
Diodes Zetex Semiconductors Limited is an ISO 9001 and TS16949 certified semiconductor manufacturer.
To ensure quality of service and products we strongly advise the purchase of parts directly from Diodes Incorporated or one of our
regionally authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com or www.diodes.com.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales channels.
ESD (Electrostatic discharge)
Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices.
The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent
of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time.
Devices suspected of being affected should be replaced.
Green compliance
Diodes Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or
exceeding regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to reduce the use of hazardous substances and/or emissions.
All Diodes Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance
with WEEE and ELV directives.
Product status key:
“Preview”
Future device intended for production at some point. Samples may be available
“Active”
Product status recommended for new designs
“Last time buy (LTB)”
Device will be discontinued and last time buy period and delivery is in effect
“Not recommended for new designs” Device is still in production to support existing designs and production
“Obsolete”
Production has been discontinued
Datasheet status key:
“Draft version”
This term denotes a very early datasheet version and contains highly provisional information, which
may change in any manner without notice.
“Provisional version”
This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance.
However, changes to the test conditions and specifications may occur, at any time and without notice.
“Issue”
This term denotes an issued datasheet containing finalized specifications. However, changes to
specifications may occur, at any time and without notice.
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