Part Number: BQ2000
Hi
Thank you very much a lot of help .
Our Customer started MP with BQ2000 wit NiMH Battery.
Customer checking Charge Current spec as Factory Shipping test.
But many BQ2000 Board Charge Current shift to Small and Bug value.
We have very simple question for EVM circuit .
1) About EVM FET Gate Pin control circuit.
We use FET as Charge current control with BQ2000 and almost same schematic BQ2000 EVM
But this FET control by Q2 and Q3 Transistor and MOD Pin .
My question for Could you tell us about these Q2 and Q3 Transistor Purpose and Operating principle.
Yes we know these Transistor and MOD output control FET gate Pin.
But Sorry.. I don't understand this behavior well.
2) About D7 MMSZ5234 BT7
This Q2 and Q3 control Q1 FEt gate and connected D7 ZD Diode MMS5234BT1.
Our customer this D7 ZD diode change to normal Resister 100 ohm.
Is this Ok ?? Because of we checked Current waveform and we found Charge current DC offset change to upper side. (DC Level changed to Big ).
If DC Level will shift , this mean Average Current Waveform change to small or big .
My guess this Q3 Transistor and D7 ZD Diode make Voltage Regulator and connect to FET gate , Yes DC Bias Level fix by this Q3 and D7.
If Customer this Diode changed to Resister 100 Ohm, I think no good for FET Control.
Could you tell us side effect when D7 diode change to Resister ??
3) Charge current shift reason
We use Rsns 91ohm , and Vsns 50mV ±10mV , this mean calculate Charge Current range
I_max = Vsns ( 50mV ±10mV ) / Rsns I_max Range is 670mA - 440mA.
But many MP stage BQ2000 board Charge Current is outside the calculate I_max Range.
For instance
360mA
What causes this I_max variation? Do you know this reason ??
We understood this device is little old. But our customer want to use this device.
Thanks and Regard
March Jasper ( Japan Disty Sugimoto )
