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I was looking for a PMIC with battery charger and built-in power path when I came across one of TI's new chip. BQ25601 http://www.ti.com/product/BQ25601. while I was trying its performance and doing some tests I noticed that it cannot withstand load steps when it's working without battery and enabled charger. as long as the charger is enabled and there is no battery connected, the chip works in suspend mode and cannot respond to transient currents. although it can provide the magnitude of the current, significant deeps appear in the output at the beginning of the load step. However, the chip works perfectly with battery irrespective of how much discharge is.

Because I don't know when he is about to connect I'm after something that can work perfectly even with no battery.

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  • \$\begingroup\$ Could you please refine the language in your question? Which load steps are you talking about? To which transient current it needs to respond? Are you talking about IC behavior when a unknown (disconnected) battery is just plugged in? \$\endgroup\$ – Ale..chenski Aug 31 '17 at 19:24
  • \$\begingroup\$ I tried it with gsm module. Usually the chip enters in suspend mode when its charger is enabled and no battery is connected to it. In that node I noticed that when the gsm was transmitting there was significant drops in output. I didn't measure the time of the drop but it was something around few microseconds. Although this error is compensated instantly, gsm couldn't be supplied properly. \$\endgroup\$ – MrBit Aug 31 '17 at 20:11
  • \$\begingroup\$ My question is of there is other chip without suspend mode. \$\endgroup\$ – MrBit Aug 31 '17 at 20:16
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If you have a problem with GSM transmitter connected to the power managed by BQ25xxx IC, this is a different problem you are facing.

RF transmitters consume a lot of current (~2 A pulses) when transmitting. Apparently your power supply path is not sufficient to eliminate drops (deeps) in power supply when the radio consumes a lot of current, and the charger IC has a very little to do with this. You need to beef-up the power net with lots of low-ESR capacitance.

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  • \$\begingroup\$ Yes but I also mentioned that this is happening only when the chip is in suspend mode. If battery is present either it is charging or not the chip responds perfectly to those pulses. \$\endgroup\$ – MrBit Aug 31 '17 at 20:40
  • \$\begingroup\$ That's why I'm seeking for other chip. \$\endgroup\$ – MrBit Aug 31 '17 at 20:41
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    \$\begingroup\$ @MrBit, the design works with battery because it serves as a very big capacitor and can supply enough current to the SYS rail. If you want to work without battery, you need to substitute it with some capacitance. No "other chip" will be capable to replace this capacity. \$\endgroup\$ – Ale..chenski Aug 31 '17 at 20:47
  • \$\begingroup\$ It does work even when the battery is fully discharged (below 2,8V). The issue here is that the chip sees a battery and exits suspend mode. Battery cannot work as a capacitor in that level! \$\endgroup\$ – MrBit Aug 31 '17 at 20:51
  • \$\begingroup\$ @MrBit, then you need to find a better control of your BQ25601 IC over I2C interface. \$\endgroup\$ – Ale..chenski Aug 31 '17 at 21:12

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