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ZXLD1362ET5TA

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P25
ZXLD1362
Document number: DS33472 Rev. 6 - 2
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ZXLD1362
Typical Characteristics (cont.)
Lx on-resistance vs die temperature
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
-50 0 50 100 150 200
Die Tempe rature (C)
On-resistance (Oh
m
s)
7V
9V
12V
20V
30V
Lx on-resistance vs supply voltage
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 5 10 15 20 25 30 35
Supply Voltage (V)
On-resistance (Ohm s)
-40C
20C
150C
Vadj vs Temperature
1.244
1.246
1.248
1.25
1.252
1.254
1.256
1.258
1.26
1.262
-50 0 50 100 150 200
Temperature (C)
Vadj (V)
7V
9V
12V
20V
30V
ZXLD1362
Document number: DS33472 Rev. 6 - 2
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ZXLD1362
Application Information
Setting Nominal Average Output Current with External Resistor R
S
The nominal average output current in the LED(s) is determined by the value of the external current sense resistor (R
S
) connected between V
IN
and I
SENSE
and is given by:
I
OUTnom
= 0.1/R
S
[for R
S
> 0.1]
The table below gives values of nominal average output current for several preferred values of current setting resistor (R
S
) in the typical
application circuit shown on page 1:
R
S
(Ω)
Nominal Average
Output Current
(mA)
0.1 1000
0.13 760
0.15 667
The above values assume that the ADJ pin is floating and at a nominal voltage of V
REF
(= 1.25V). Note that R
S
= 0.1 is the minimum allowed
value of sense resistor under these conditions to maintain switch current below the specified maximum value.
It is possible to use different values of R
S
if the ADJ pin is driven from an external voltage. (See next section).
Output Current Adjustment by External DC Control Voltage
The ADJ pin can be driven by an external dc voltage (V
ADJ
), as shown, to adjust the output current to a value above or below the nominal
average value defined by R
S
.
GND
ZXLD1362
ADJ
GND
+
DC
The nominal average output current in this case is given by:
I
OUTdc
= (V
ADJ
/1.25) x (100mV/R
S
) [for 0.3< V
ADJ
<2.5V]
Note that 100% brightness setting corresponds to V
ADJ
= V
REF
. When driving the ADJ pin above 1.25V, R
S
must be increased in proportion to
prevent I
OUTdc
exceeding 1A maximum.
The input impedance of the ADJ pin is 50kΩ ±25% for voltages below V
REF
and 14.2kΩ ±25% for voltages above V
REF
+100mV.
Output Current Adjustment by PWM Control
Directly driving ADJ input
A Pulse Width Modulated (PWM) signal with duty cycle D
PWM
can be applied to the ADJ pin, as shown below, to adjust the output current to a
value above or below the nominal average value set by resistor R
S
:
PWM
GND
0V
V
ADJ
GND
ZXLD1362
ADJ
ZXLD1362
Document number: DS33472 Rev. 6 - 2
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ZXLD1362
Application Information (cont.)
Driving the ADJ Input via Open Collector Transistor
The recommended method of driving the ADJ pin and controlling the amplitude of the PWM waveform is to use a small NPN switching transistor
as shown below:
PWM
GND
ZXLD1362
ADJ
GND
This scheme uses the 50k resistor between the ADJ pin and the internal voltage reference as a pull-up resistor for the external transistor.
Driving the ADJ Input from a Microcontroller
Another possibility is to drive the device from the open drain output of a microcontroller. The diagram below shows one method of doing this:
GND
ZXLD1362
ADJ
MCU
3.3k
If the NMOS transistor within the microcontroller has high Gate / Drain capacitance, this arrangement can inject a negative spike into ADJ input
of the 1362 and cause erratic operation but the addition of a Schottky clamp diode (cathode to ADJ) to ground and inclusion of a series resistor
(3.3k) will prevent this. See the section on PWM dimming for more details of the various modes of control using high frequency and low
frequency PWM signals.
Shutdown Mode
Taking the ADJ pin to a voltage below 0.2V for more than approximately 100µs will turn off the output and supply current to a low standby level
of 20µA nominal.
Note that the ADJ pin is not a logic input. Taking the ADJ pin to a voltage above V
REF
will increase output current above the 100% nominal
average value. (See page 18 graphs for details).
Soft-Start
An external capacitor from the ADJ pin to ground will provide a soft-start delay, by increasing the time taken for the voltage on this pin to rise to
the turn-on threshold and by slowing down the rate of rise of the control voltage at the input of the comparator. Adding capacitance increases
this delay by approximately 200µs/nF. The graph below shows the variation of soft-start time for different values of capacitor.
40 60020 80100120
CAPACITANCE (nF)
Soft Start Time vs. Capacitance from
ADJ Pin to Ground
16
14
12
10
4
2
0
-2
8
6
S
O
F
T
S
T
A
R
T
T
IM
E
(
m
s
)
V
IN
= 24V, R
S
= 0.1, L = 68µH, 22nF on ADJ
Soft-start operation. Output current (Ch2) and LX voltage (Ch1)
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ZXLD1362ET5TA

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Buy ZXLD1362ET5TA
Manufacturer:
Diodes Incorporated
Description:
LED Lighting Drivers 1A/60V LED DRIVER
Lifecycle:
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