ZXLD1366EN8TC Diodes Zetex, ZXLD1366EN8TC Datasheet - Page 19

• Manufacturer Part Number: ZXLD1366EN8TC
• Description: SEMICONDUCTOR OTHER
• Manufacturer: Diodes Zetex

Specifications of ZXLD1366EN8TC

• Constant Current: *
• Constant Voltage: *
• Topology: *
• Number Of Outputs: *
• Internal Driver: *
• Type - Primary: *
• Type - Secondary: *
• Frequency: *
• Voltage - Supply: *
• Voltage - Output: *
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Operating Temperature: *
• Current - Output / Channel: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ZXLD1366EN8TCTR

A Product Line of
Diodes Incorporated
ZXLD1366
Application Information
(Continued)
PWM
V
ADJ
ADJ
ZXLD1366
0V
GND
GND
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:
ADJ
ZXLD1366
PWM
GND
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:
MCU
3.3k
ADJ
ZXLD1366
GND
If the NMOS transistor within the microcontroller has high Gate / Drain capacitance, this arrangement can inject a negative
spike into ADJ input of the ZXLD1366 and cause erratic operation but the addition of a Schottky clamp diode (eg Diodes Inc.
SD103CWS) 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 65μA nominal.
Note that the ADJ pin is not a logic input. Taking the ADJ pin to a voltage above VREF will increase output current above the
100% nominal average value. (See page 18 graphs for details).
19 of 30
ZXLD1366
March 2011
www.diodes.com
© Diodes Incorporated
Document number: DS31992 Rev. 6 - 2