Post Go back to editing

Measurement for phase margin of LT3599

Category: Hardware
Product Number: LT3599

Hello

I have a question for measuring phase margin of LT3599.

We try to measure phase margin LT3599 on our customer’s board.
They use 15 LEDs for their application, Vout is typically 14.5V@VIN=10V, each LED current is 50 mA.
(5 LEDs per 1 string, 3 string total, ues from LED1 pin to LED3 pin, between LED3 pin and LED4 pin is shorted, DISABLE4 pin is shorted to VREF pin)
But LEDs is not connected between VOUT pin and LEDx pin of LT3599 for the board I received from them.

We plan to measure phase margin LT3599 without LEDs as follow.
Is it possible to measure with this method?
Please let me know if I need to measure in other ways.

Load resistance is connected between VOUT pin and GND for IOUT=150mA.
Injection resistance(75 ohm) is connected between VO_SW pin and topside feedback resistance.
Firstly ,between LED1 and LED3 is shorted and supplied 1V or more to avoid LED OPEN DETECTION(LED pin voltage>0.3V).
VIN=10V
PWM is always High for Duty cycle=100%.

Best Regards
nozawa

Parents Reply Children