BQ27421-G1: about GPOUT pin

Mitsuru Matsuo

Prodigy 210 points

Part Number: BQ27421-G1

GPOUT pin is defined as a open-drain output pin in the datasheet.

But,in SHUTDOWN mode,GPOUT should be inputted a toggling signal to exit.

Although GPOUT is a output pin,why can it be inputted a toggling signal?

Please teach me why GPOUT can input a toggling signal and show me the mechanizm.

over 5 years ago

0 Dominik Hartl11 over 5 years ago

TI__Guru 61536 points

GPOUT has a simple edge detection circuit that is active when the rest of the gauge is shut down. It is not configured as an input in regular gauging (non-shutdown mode).

0 Mitsuru Matsuo over 5 years ago in reply to Dominik Hartl11

Prodigy 210 points

I have some quetions in below.

1.Inputting a toggling signal in GPOUT in shutdown mode,I'd like to know the reason why the fuel gauge is in normal condition.

and I'd like to know the internal processing how to exit the shut down mode as detaile as possible if you can.

2.We decide to judge the wake-up from the shutdown mode by waching 1.8V of the VDD.

Our judgement is OK?

3.I'd like to know the typecal period time from when GPOUT detects the low voltage of a toggling signal to when VDD pin becomes 1.8V(wake-up from the shut down mode).

0 Dominik Hartl11 over 5 years ago in reply to Mitsuru Matsuo

TI__Guru 61536 points

#1: The gauge is in normal mode after a reset (power on or via reset command or a watchdog timer reset). The LDO is on in normal mode. The gauge has three low power modes: sleep, hibernate and shutdown. In sleep and hibernate, the gauge is still on in the sense that it will periodically wake up (e.g. sleep) or that a large current (wake threshold) will wake up the gauge. In shutdown mode, the gauge is powered off (LDO is off) and only a small auxiliary circuit is powered on that monitors the state of the GPOUT pin (in this mode, it's not an output but an input).

#2: Yes, the LDO is off in shutdown mode.

#3: The LDO comes on about 1.5ms after the gauge is turned on. Note that valid gauging results will take a lot longer (at least 1 second, longer (multiples of 1 second) if voltage isn't stable and the gauge averages this to get a better DOD0 estimate).