Datasheet

Vbat
VstorV_BAT-OK
Vphase
Test Summary www.ti.com
3.3.4 BAT_OK Indication as Battery Charges/Discharges
1. Connect scope probes CHI→CH4: V
PHASE
(TP16), V
STOR
, V
BAT_OK
, V
BAT
and vary charge element from
zero voltage to 3.15V and back down to 1.8V and observe the BAT_OK signal.
Initially P/S#1 is set to 1V and the battery is adjusted to OV (simulated battery), which clamps V
STOR
to
~0.5V (lower body diode drop due to lower current). As the battery voltage is swept higher one can see
the different phases discussed earlier. Once the output gets to ~2.8V the BAT_OK signal goes high. Note
that the BAT_OK signal goes low once the battery is discharged to ~2.34V.
This signal’s high and low threshold can be programmed by R7, R8 and R9 to give an indication to the
host when the battery is good (Signal high – has enough energy to complete the designed task) and when
the battery is discharged (Signal low – system needs to be disabled or low power mode so the battery can
recharge).
Figure 5. BAT_OK High/Low 2.8V/2.34V – Ramping Battery from 0V to 3.1V (OV) and Down to 1.8V.
3.3.5 Basic PFM Switching Waveform, Vin = 1V, Vbat = 2.5V
1. Set up scope as follows: CHI→CH4: V
PHASE
(TP16), V
STOR
, V
P/S #1
, V
IN
, 10µs/DIV.
8
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A–October 2011–Revised October 2011
Energy Harvester Applications
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