TPIC74100EVM: Vout drop when Vin is adjusting & Vout couldn't be generated when Vin < 4.7V

Roy Chou1

Part Number: TPIC74100EVM

Hi Team,

I have two questions of using TPIC74100EVM.

1. Vout drop when Vin is adjust from 5V to 6.5V. It happened in Vin is about 5.8V. the switching is changing from Q1/Q2 to Q3/Q4, the drop voltage is about 200mV. Could I add some components to eliminate the drop voltage?

2. Vout couldn't be generated when Vin < 4.7V, the feature of datasheet said the Vin could operate when Vin = 1.5V-40V, could I set some pin to let IC could work in 1.5V-40V?

ps. I add Vin in C5/C6 of EVM.

Regards,

Roy

over 5 years ago

0 Jasper Li over 5 years ago

TI__Mastermind 46905 points

Hi Roy,

what is the output current in the measurement in the first/Second observation?

in the second observation, did you startup the IC firstly before decrease the VIN to 4.7V?

0 Roy Chou1 over 5 years ago in reply to Jasper Li

TI__Genius 16110 points

Hi Jasper,

1. I have measured 0.2A/0.4A/0.6A, They all have the issue.

2. no, I start up the IC when Vin is 4.7V.

Regards,

Roy

0 Roy Chou1 over 5 years ago in reply to Roy Chou1

TI__Genius 16110 points

Hi Team,

Any comments?

Roy

0 Jasper Li over 5 years ago in reply to Roy Chou1

TI__Mastermind 46905 points

Hi Roy,

as described in datasheet page 14, the device does transit from boost mode to buck mode at VIN=5.8V condition. so it can't be eliminated. but i think we can try to increase output capacitor to reduce the ripple during this period.

the device need to startup at VIN> 4.7V firstly before drop down to 1.5V. and the output current is small at low input condition, refer to figure 3

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TPIC74100EVM: Vout drop when Vin is adjusting & Vout couldn't be generated when Vin < 4.7V