I have an application where there is no battery on the output, just a large capacitance. The unit is charged via adapter. So the circuit pinout is as follows:
On bq24050 EVM
1 = input voltage @ 5V
2= Iset @750R which I believe sets the fast charge to 720mA
3= Vss
4 = Preterm @ 1k with JMP2 connected
5 = D+ connected to D- (JMP6 connected) i.e. 200R
6 = D- connected to D+ (JMP6 connected)i.e. 200R
7 = ISET2 LOW (JMP3 on pins 2 and 3)
8 = connected to the charge LED with JMP4 connected
9 = Open, JMP5 removed
10 = Connected to capacitance of about 120mF
For some reason, I am unable for the device to realize it is connected to an adapter, enter TDDM mode and charge cap at full ISET current.
From what I understand,
- with JMP6 I tell the device it is connected to Adapter
- with JMP5 open, I tell the device that there is no battery and it must enter TDDM mode
- I dont change the configuration of JMP3 (Iset2) at any point. This means charge current stays at detected level which should be Iset
I always seem to go into a 10mA pre-charge mode and then ultimately turns on the CHG LED at which point the cap charges up quickly.
After some further testing, the additional information is as follows:
When the power is connected, the unit does a precharge at 15mA. No adjustment that I make to PRETERM resistor changes this.
At some point (roughly 2.5V) the current increases (but nowhere near 500 or 700mA) and the output goes up to 4.2V
The Charge LED comes on, which is weird, since i thought that it does not during TTDM mode.
I would appreciate any help, ideas, clarification on this problem. I am available to try any ideas you might have on the EVM.
