TPS92201: TPS92201, will EN Pin pull down system voltage when it is set to low ?

XU KE

Part Number: TPS92201

Hi, There

We just complete an application. We use STM8S003 GPIOs connecting to TPS92201 to control a LED, one gpio to en, the other one to pwm. They are both direct connection without any resistor in the middle. System use 5V suppy. PWM is set to 40kHz in the range of TPS92201 spec. LED can be modulated properly as PWM duty cycle changed by STM8S. There's only one problem, it will pull system voltage 5V down to 0 when STM8S is set the en pin low to disable the TPS92201 and to complete shutdown the led.

Just wondering that, is the VIN pin of TPS92201 connected internalll to EN pin without any resistor that cause the problem?

kind regards

Frank

7 个月前

0 FRANK1 7 个月前

TI__Genius 14790 points

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0 XU KE 7 个月前回复 FRANK1

Prodigy 10 points

Hi Frank1,

There's another TPS92201 application found this morning designed by TI. Please refere to the attached diagram.

I guess R2 + R3 is to make sure EN pin is either HIGH or LOW. This is easy to understand. While R1 in the diagram is a bit strange cos R1 will consume quite large current if the load side led has significant current. This could lead thermal issue at R1 as well as the selection of R1. So, another two questions as follow,

1. Do we still need R2+R3 if we use MCU? R2+R3 is more suitable for uncertain input, MCU GPIO shouldn't have the problem if settng is correct. Or R2+R3 has to be there, otherwise the early problem will occur?

2. Could the TI designer explain the reason using R1, this could help understand how TPS92201 works as well as solve the early problem.

kind regards

Frank