BQ24773: BQ24773 can work without battery with load on default setting ..?

Hello Joel, 

BATPRES pin pull down by using 100K resistor..? Battery is contentiously present with system, is it right ..?

1) It cannot function standalone to charge the battery
- what you mean ..? can you describe the reason please 

In my application need to self start Initially the BMS system, after that BMS system is going to configure as per the requirements, is it possible with BQ24773..? that's why we looking for standalone functionality.

System behavior with load and without load (LED load- 500mW)
We observe,

1. BQ24773 not going to work with load on default configuration (Without configuration)

Observe same performance with load 2) Yes, it can function with the default settings. The load will be dictated by the input current limit setting. Without a battery, the system voltage will collapse is the input current hits the register setting threshold. System voltage is going to collapse ..? how to resolve the issue

2. When battery is connected, observe battery discharging when adapter(5V/2A) present on above mention load ..? 
when we follow the this Cycle, 1. power On Adapter(Vsys-4.4) 2.configure system by using arduino (Vsys-4.2) 3.Connected load (Vsys-4.2) 4.disconnect adapter (Vsys-3.8, Discharge current-80mA) 5.reconnect adapter and reconfigure system(Vsys-4.2, charging current-20mA)

when we try only 4 and 5 step again, its not working ..?

There is anything which we are missing or It's BQ24773 behavior ..? 

Thanks and Regards, 
Rahul Surawase

Hey Rahul,

Using the 100kOhm is fine. This is how it is done on our EVM. This indicates to the charger that the battery is present. 

For 1) What I mean to say is that the charging is not automatic. In order to start charging, a valid adapter must be present AND you must set the ChargeCurrent() register. Please see section 8.6.6 Setting the Charge Current for a description of the charge current register. 

However, by default, your adapter CAN power the system rail. Your host controller just needs to program the charge current in order to charge the battery. 

For 2) Your input source must be able to handle the system power. You mention the system load is 500mW. What is the capability of your input adapter? By default, the input current of the charger is ~3A. If the input current hits this threshold, the system voltage will fall in order to regulate the input current to 3A. You can increase this threshold through host control.

For the other 2) how are you configuring your system? And you mean when you perform steps 4-5 without doing steps 1-3, you cannot get the same behavior?

Regards,

Joel H

Hello Joel, 
                 As i mention Input adapter is 5V/2A,  For 2) Your input source must be able to handle the system power. You mention the system load is 500mW. What is the capability of your input adapter? By default, the input current of the charger is ~3A. If the input current hits this threshold, the system voltage will fall in order to regulate the input current to 3A. You can increase this threshold through host control. System load is around 500mW, there is no battery connected to the charger in that case also collapse the Vsys voltage, charger is running on Default configuration.

How to avoid the Vsys voltage Collapse issue..? this is not unacceptable to our system.

Our requirement is, 
1. When charge on with input adapter source with default configuration 
2. Charger is running without battery 
3. Load is connected Booster Output which, booster(TPS61088) use to provide constant 5V to load 
4. Host is present at load end, when charger on need to handle Load(Host-Arduino) on default configuration 
5. Host is going to configure the charger 

Issue is Vsys voltage going to collapse(2.5V), Booster not going to generate 5V (min I/P voltage is -2.7), host is not going make on and system is not going to configure 

Please provide some solid suggestion to fix this issue 

Thanks and regard,
Rahul Surawase  

Hello Joel, 
                    Almost observe the same behavior of signal  which you mention above and in datasheet 

    result is same ..!

we also observe when system is power 'ON'  on battery and load is connected, its shutdown the load  at 13min almost check it 4 time after the power on and after 13 min it going reboot the system and started miss behaving          

we also try to test it on performance mode Reg12(15), observe the same results ...

Thanks and regards,

Rahul 

Hey Rahul,

Which waveform is which above? I did not notice any labels. 

And I am now understanding that your device works (i.e. system voltage is regulated) for 13min? Then you suddenly remove power and reapply it and it does not work? When it does not work, you mean there is no system voltage? 

Is there any specific event occurring at 13min on the load side or on the Raspberry Pi side? Will it work beyond 13minutes if power is not removed?

Regards,

Joel H

Hello Joel, 
                 As i mention before, It work beyond 13 min if power is not removed but my question was without configuration its not working with load, why..? what is the alternative for this ...? because my host is power by Charging IC.

It's work beyond only when i follow this BQ24773 starting steps,
1. BQ24773 is power by Adapter
2. Configure the System (configure by using external Arduino)
3. connect Load(Raspberry PI)
It's work in both condition, with or without battery connection 

   Then you suddenly remove power and reapply it and it does not work? , Yes 

BQ24773 is power by Adapter, configure the System, Connect Battery and connect Load(Raspberry PI) its working properly when i disconnect adapter also work properly for only 13min after that load reset continuously and when i reconnect adapter, configure the system then also raspberry PI continuously reset ..? 

Is there any specific event occurring at 13min on the load side or on the Raspberry Pi side? Is this matter ....?
May be there is some event occur in raspberry side and going to sink more current form source but battery is 5Ah and able to handle 4A peak current contentious discharging current is 2.5A

 Will it work beyond 13minutes if power is not removed? Yes

Thanks and Regards,

Rahul Surawase