Battery Low Detect Circuit Operation - Oki ML63611 User Manual

14.5

Battery Low Detect Circuit Operation

The battery low circuit is turned ON or OFF by ENBL (bit 2 of BLDCON), and outputs to BLDF (bit 3 of
BLDCON) the result of a comparison with the judgment voltage.
ENBL is the enable control bit for the battery low detect circuit. Setting ENBL to "1" turns ON the battery low
detect circuit. Setting ENBL to "0" turns OFF the battery low detect circuit and BLD current supply drops to zero.
BLDF is the judgment result flag. If BLDF is "1", the power supply voltage is lower than the judgment voltage. If
BLDF is "0", the power supply voltage is higher than the judgment voltage. BLDF is valid when ENBL is "1".
The judgment circuit of the battery low detect circuit requires time to become stable. Therefore, after setting
ENBL to "1", wait at least 1 ms before reading BLDF. No load should be applied to the power supply voltage
during the detection.
Figure 14-2 shows an example operation timing.
Operation
ENBL
Judgment voltage
Vcmp
BLDF
Figure 14-2 shows the following operations.
ENBL is set to "1" to turn ON the BLD.
Operation starts with no load applied to power supply system and waits for BLD stabilization time
interval (at least 1 ms).
Judgment result flag (BLDF) is read.
ENBL is cleared to "0".
OPTION A (C): 1.5 V (3.0 V), Without regulator
circuit for LCD bias
Set ENBL
V
Vcmp
SS
"1" or "0"
BLD stabilization time
(wait at least 1 ms)
Figure 14-2 Operation Timing Example
14 – 3
Chapter 14 Battery Low Detect Circuit (BLD)
Reset ENBL
Read BLDF
OPTION B (D): 1.5 V (3.0 V), With regulator
ML63611 User's Manual
circuit for LCD bias