ZXLD1370

ZXLD1370

Document number: DS32165 Rev. 4 - 2

25 of 36

www.diodes.com

March 2011

© Diodes Incorporated

A Product Line of

Diodes Incorporated

Figure 30. PWM dimming from open collector switch

Figure 31. PWM dimming from MCU

LED current can be adjusted digitally, by applying a low

frequency PWM logic signal to the PWM pin to turn the

controller on and off.

This will produce an average

output current proportional to the duty cycle of the control

signal.

During PWM operation, the device remains

powered up and only the output switch is gated by the

control signal.

The PWM signal can achieve very high LED current

resolution.

In fact, dimming down from 100% to 0, a

minimum pulse width of 2µs can be achieved resulting in

very high accuracy. While the maximum recommended

pulse is for the PWM signal is10ms.

PWM

0V

< 10 ms

0V

2µs

Gate

< 10 ms

2µs

Figure 32. PWM dimming minimum and maximum pulse

The device can be put in standby by taking the PWM pin to ground, or pulling it to a voltage below 0.4V with a suitable open

collector NPN or open drain NMOS transistor, for a time exceeding 15ms (nominal). In the shutdown state, most of the

circuitry inside the device is switched off and residual quiescent current will be typically 90µA. In particular, the Status pin

will go down to GND while the FLAG and REF pins will stay at their nominal values.

Fig 33. Stand-by state from PWM signal