ZXLD1356ET5TA Diodes Zetex, ZXLD1356ET5TA Datasheet - Page 5

• Manufacturer Part Number: ZXLD1356ET5TA
• Description: IC LED DRIVR WHITE BCKLGT TSOT-5
• Manufacturer: Diodes Zetex
• Type: Backlight, White LEDr

Specifications of ZXLD1356ET5TA

• Topology: PWM, Step-Down (Buck)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Automotive, Backlight
• Type - Secondary: High Brightness LED (HBLED), White LED
• Frequency: 500kHz
• Voltage - Supply: 6 V ~ 60 V
• Voltage - Output: 60V
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 550mA
• Internal Switch(s): Yes
• Efficiency: 97%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ZXLD1356ET5TR

Device Description
The device, in conjunction with the coil (L1) and current sense resistor (R
converter.
Device operation
Operation can be best understood by assuming that the ADJ pin of the device is unconnected and the voltage on this pin (V
appears directly at the (+) input of the comparator.
When input voltage V
circuit. Under this condition, the (-) input to the comparator is at ground and its output is high. This turns MN on and switches
the LX pin low, causing current to flow from V
V
R1 by the current sense circuit and produces a proportional current in internal resistors R2 and R3. This produces a ground
referred rising voltage at the (-) input of the comparator. When this reaches the threshold voltage (V
switches low and MN turns off. The comparator output also drives another NMOS switch, which bypasses internal resistor R3 to
provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 15% of V
When MN is off, the current in L1 continues to flow via D1 and the LED(s) back to V
by the LED(s) and diode forward voltages to produce a falling voltage at the input of the comparator. When this voltage returns
to V
limits of V
ZXLD1356
Document number: DS33470 Rev. 3 - 2
IN
and L1 to produce a voltage ramp (V
ADJ
, the comparator output switches high again. This cycle of events repeats, with the comparator input ramping between
SENSE voltage
ADJ
Coil current
Comparator
input voltage
Comparator
output
LX voltage
± 15%.
(refer to Figure 1 - Block diagram and Figure 2 Operating waveforms)
IN
is first applied, the initial current in L1 and R
V
V
V
ADJ
IN
IN
0V
5V
0V
0V
0.15V
230mV
Figure 2. Theoretical Operating Waveforms
SENSE
ADJ
IN
) across R
to ground, via R
Toff
www.diodes.com
S
. The supply referred voltage V
Ton
170mV
5 of 29
S
, L1 and the LED(s). The current rises at a rate determined by
S
is zero and there is no output from the current sense
S
), forms a self-oscillating continuous-mode buck
Diodes Incorporated
IN
200mV
. The current decays at a rate determined
A Product Line of
0.15V
SENSE
V
V
SENSE-
SENSE+
I
I
I
ADJ
OUTnom
OUTnom
OUTnom
is forced across internal resistor
ADJ
.
+15%
-15%
ADJ
), the comparator output
© Diodes Incorporated
ZXLD1356
December 2010
ADJ
)