A Product Line of
Diodes Incorporated
ZXLD1356
High accuracy 550mA, 60V LED driver with internal switch
Description
The ZXLD1356 is a continuous mode
inductive step-down converter, designed for
driving single or multiple series connected
LEDs efficiently from a voltage source higher
than the LED voltage. The device operates
from an input supply between 6V and 60V and
provides an externally adjustable output
current of up to 550mA. Depending upon
supply voltage and external components, this
can provide up to 30 watts of output power.
The ZXLD1356 includes the output switch and
a high-side output current sensing circuit,
which uses an external resistor to set the
nominal average output current.
Output current can be adjusted above, or
below the set value, by applying an external
control signal to the 'ADJ' pin.
The ADJ pin will accept either a DC voltage or a
PWM waveform. Depending upon the control
frequency, this will provide either a continuous
(dimmed) or a gated output current. Soft-start
can be forced using an external capacitor from
the ADJ pin to ground.
Applying a voltage of 0.2V or lower to the ADJ
pin turns the output off and switches the device
into a low current standby state.
Features
•
•
•
•
•
•
•
•
Typically better than 0.8% output current
accuracy
Available in thermally enhanced DFN
package
Simple and with low part count
Single pin on/off and brightness control
using DC voltage or PWM
PWM resolution up to 1000:1
High efficiency (up to 97%)
Wide input voltage range: 6V to 60V
Inherent open-circuit LED protection
Applications
•
•
•
•
•
•
•
•
•
Low voltage halogen replacement LEDs
Automotive lighting
Low voltage industrial lighting
LED back-up lighting
Illuminated signs
Emergency lighting
SELV lighting
LCD TV backlighting
Refrigeration lights
Pin connections
Typical application circuit
D1
V
IN
(24V)
Rs
0.36
LX
1
GND
2
ADJ
3
TSOT23-5
Top view
5
V
IN
LX
1
GND
2
6
V
IN
5
GND
4
I
SENSE
DFN633
Top view
4
I
SENSE
ADJ
3
L1
C1
4.7 F
V
IN
I
SENSE
LX
100nF
ADJ
ZXLD1356
GND
GND
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ZXLD1356
Absolute maximum ratings (voltages to GND unless otherwise stated)
Input voltage (V
IN
)
I
SENSE
voltage (V
SENSE
)
LX output voltage (V
LX
)
Adjust pin input voltage (V
ADJ
)
Switch output current (I
LX
)
Power dissipation (P
tot
)
(Refer to package thermal de-rating curve on page 26)
-0.3V to +60V (65V for 0.5 sec)
+0.3V to -5V (measured with respect to V
IN
)
-0.3V to +60V (65V for 0.5 sec)
-0.3V to +6V
0.65A
SOT23-5; 1W : DFN; 1.8W
-40 to 125°C
-55 to 150°C
150°C
Operating temperature (T
OP
)
Storage temperature (T
ST
)
Junction temperature (T
j MAX
)
These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure. Operation
at the absolute maximum ratings, for extended periods, may reduce device reliability.
Thermal resistance
Junction to ambient (R
JA
)
Junction to board (R
ΨJB
)
Junction to case (R
JC
)
TSOT23-5
82°C/W
33°C/W
-
DFN
44°C/W
-
14°C/W
Electrical characteristics
(test conditions: V
IN
=24V, T
amb
=25°C unless otherwise stated)
(a)
Symbol
V
IN
V
SU
V
SD
I
INQoff
I
INQon
Parameter
Input voltage
Internal regulator start-up threshold
Internal regulator shutdown threshold
Quiescent supply current
with output off
Quiescent supply current
with output switching
(c)
ADJ pin grounded
4.4
Conditions
See note
(b)
Min.
6
Typ.
4.85
4.75
65
1.6
108
Max.
60
5.2
Unit
V
V
V
A
mA
V
SENSE
ADJ pin floating,
L=68 H, 3 LEDs,
f = 360kHz
Mean current sense threshold voltage Measured on I
SENSE
pin
(Defines LED current setting accuracy)
with respect to V
IN
V
ADJ
= 1.25V; V
IN
=18V
Sense threshold hysteresis
I
SENSE
pin input current
Internal reference voltage
V
SENSE
= V
IN
-0.2
Measured on ADJ pin
with pin floating
195
200
205
mV
V
SENSEHYS
I
SENSE
V
REF
±15
4
1.25
50
0.3
V
ADJ
falling
0.15
0.2
2.5
0.27
10
%
A
V
ppm/°C
V
V
V
REF
/ T Temperature coefficient of V
REF
V
ADJ
V
ADJoff
External control voltage range on ADJ
pin for DC brightness control
(d)
DC voltage on ADJ pin to switch
device from active (on) state to
quiescent (off) state
NOTES:
(a) Production testing of the device is performed at 25°C. Functional operation of the device and parameters specified over
a -40°C to +105°C temperature range, are guaranteed by design, characterization and process control.
(b) V
IN
> 16V to fully enhance output transistor. Otherwise out current must be derated - see graphs. Operation at low
supply may cause excessive heating due to increased on-resistance. Tested at 7V guaranteed for 6V by design.
(c) Static current of device is approximately 700 A, see Graph, Page 17
(d) 100% brightness corresponds to V
ADJ
= V
ADJ(nom)
= V
REF
. Driving the ADJ pin above V
REF
will increase the V
SENSE
.
threshold and output current proportionally.
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ZXLD1356
Electrical characteristics
(test conditions: V
IN
=24V, T
amb
=25°C unless otherwise stated)
(
cont.)
Symbol
V
ADJon
Parameter
DC voltage on ADJ pin to switch
device from quiescent (off) state
to active (on) state
Resistance between ADJ pin
and V
REF
Continuous LX switch current
LX Switch ‘On’ resistance
LX switch leakage current
PWM frequency <300Hz 0.001
PWM amplitude = V
REF
Measured on ADJ pin
See note
(*)
Time taken for output
current to reach 90% of
final value after voltage
on ADJ pin has risen
above 0.3V
Requires external
capacitor 22nF. See
graphs for more details
ADJ pin floating
L = 68 H (0.36 )
I
OUT
= 0.55A @ V
LED
=
3.6V
Driving 3 LEDs
LX switch ‘ON’
LX switch ‘OFF’
1000:1
5:1
2
ms
@ I
LX
= 0.55A
0.5
Conditions
V
ADJ
rising
Min.
0.2
Typ.
0.25
Max.
0.3
Unit
V
R
ADJ
I
LXmean
R
LX
I
LX(leak)
0< V
ADJ
< V
REF
V
ADJ
> V
REF
+100mV
30
10.4
50
14.2
65
18
0.55
0.75
5
1
k
k
A
A
D
PWM(LF)
Duty cycle range of PWM signal
applied to ADJ pin during low
frequency PWM dimming mode
Brightness control range
DC
ADJ (*)
DC Brightness control range
T
SS
Start up time
f
LX
Operating frequency
(See graphs for more detail)
360
130
(†)
70
(†)
800
500
0.3
0.7
kHz
ns
ns
ns
kHz
T
ONmin
T
OFFmin
Minimum switch ‘ON’ time
Minimum switch ‘OFF’ time
T
PWmin_REC
Recommended minimum switch LX switch 'ON' or ‘OFF’
pulse width
Recommended maximum
f
LXmax
operating frequency
D
LX
Recommended duty cycle range
of output switch at f
LXmax
NOTES:
(*) Ratio of maximum brightness to minimum brightness before shutdown V
REF
= 1.25/0.3. V
REF
externally driven to 2.5V,
ratio 10:1.
(†) Parameters are not tested at production. Parameters are guaranteed by design, characterization and process control.
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ZXLD1356
Pin description
LX
1
GND
2
ADJ
3
TSOT23-5
Top view
5
V
IN
LX
1
GND
2
6
5
4
DFN633
Top view
V
IN
GND
I
SENSE
4
I
SENSE
ADJ
3
Name
LX
GND
ADJ
Pin no.
TSOT
DFN
Description
Drain of NDMOS switch
Ground (0V)
Multi-function On/Off and brightness control pin:
• Leave floating for normal operation.(V
ADJ
= V
REF
= 1.25V giving
nominal average output current I
OUTnom
= 0.2V/R
S
)
• Drive to voltage below 0.2V to turn off output current
• Drive with DC voltage (0.3V < V
ADJ
< 2.5V) to adjust output current
from 25% to 200% of I
OUTnom
• Connect a capacitor from this pin to ground to set soft-start time.
Soft start time increases approximately 0.2ms/nF
Connect resistor R
S
from this pin to V
IN
to define nominal average
output current I
OUT
nom = 0.2V/R
S
(Note: R
SMIN
= 0.36 with ADJ pin open-circuit)
Input voltage (6V to 60V). Decouple to ground with 4.7 F or higher
X7R ceramic capacitor close to device
Not internally connected. Connect to ground plane to improve thermal
efficiency
1
2
3
1
2,4
3
I
SENSE
4
5
V
IN
Tab
5
6
Ordering information
Device
ZXLD1356ET5TA
ZXLD1356DACTC
Reel size
(inches)
7”
13”
Reel width
(mm)
8
12
Quantity
per reel
3,000
3,000
Device mark
1356
1356
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ZXLD1356
D1
V
IN
R
S
L1
5
V
IN
4
I
SENSE
1
LX
5V
C1
4.7 F
Voltage
regulator
R1
-
+
0.2V
-
+
Low voltage
detector
MN
Adj
3
R4
50K
R5
20K
600KHz
R2
-
+
D1
1.25V
-
+
1.35V
R3
Gnd
2
Figure 1
Block diagram - pin connection for TSOT package
Issue 2 - September 2008
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