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TPS62125: EN_HYS pin used as Low Battery Indicator while step-down is still enabled

Part Number: TPS62125
Other Parts Discussed in Thread: TPS3710

Hi all,

TPS62125 (powered with a 16.5V battery and configured for V_OUT=3.3V) has a PG pin to test output voltage but no Low Battery Indicator (LBI). As I have very tough space and target price constraints I cannot use a separate voltage detector (e.g. TPS3710) to test if nominal battery voltage (16.5V) falls below a predefined threshold (e.g. 15V).

It seems anyway that EN_YS pin could be used as an LBI, As described on the datasheet it is an open-drain and is pulled to GND when 'voltage on the EN pin is below the comparator threshold V_TH_EN_ON of typ. 1.2 V'. In particular 'The pin is pulled to GND once the falling voltage on the EN pin trips the threshold V_TH_EN_OFF (1.15 V typical)'.

So, if I connect EN pin to V_IN through a 1.2M resistor and to GND through a 100k rsistor, I expect that EN_HYS pin (simply pulled-up to 3.3V with a 20kohm resistor) is pulled to GND whenever V_IN falls below 15V, working as an LBI (of course while TPS62125 is still enabled and continues to regulate). Is this correct or cannot it work like this for some other reason?

Many hanks in advance.

Best regards,


  • Mauro,

    You might be able to do that, but you will have a vary narrow window of operation.  The EN_HYS pin will be held low until the input voltage reaches the EN threshold.  So the TSP62125 will be come enabled at Vin = 15.08 V minimum, 15.6 V typical and 16.12 V maximum, and the EN_HYS pin will be open drain.  The maximum operating input voltage is 17 V, so you may only have a 880 mV window for operation.  As the battery voltage decreases, The TPS62125 will shut down and the EN_HYS pin will be pulled low when Vin = 14.56 V minimum, 14.95 V typical and 15.47 V maximum.  If these constraints meet your requirements, then it may work for you.  Remember, maximum operating voltage is 17 V.