SM6781BV Datasheet, PDF (6/10 Pages) Nippon Precision Circuits Inc – Ni-MH/Ni-Cd Battery Charger IC

SM6781BV
Initialization
The SM6781BV charging operation commences when power is applied or when a battery is inserted (standby
mode released). Approximately 200ms are required when operation starts to initialize all internal circuits.
When initialization finishes, the charging mode is determined by the BATT input voltage and the timer mode.
Battery Voltage Check
When the BATT input voltage is outside the permitted range, quick charge stops. At this point, the maximum
quick charge time count and -∆V prohibit time counters also stop. When the BATT input voltage comes back
within the permitted range, quick charge and timer stop conditions are released. When quick charge mode is
restarted, the saved peak voltage data is reset (cleared to 0V).
–∆V Detection Prohibit Time
–∆V detection is not performed for approximately 15 minutes from when quick charge commences (quick
charge cumulative time).
CHGN Output
CHGN becomes high impedance during quick charge. CHGN goes LOW when quick charge mode finishes or
when abnormal battery voltage is detected.
Hi-Z
CHGN
Low
Quick charge Stop/Hold/INH=High
Figure 1. CHGN state
LEDN Output
LEDN is LOW during quick charge (LED is ON), and high impedance after quick charge finishes (LED is
OFF). When an abnormal battery voltage is detected before quick charge finishes, a pulse of approximately
1Hz is output (LED flashes). Also, a 1Hz pulse is output when INH is HIGH.
Hi-Z
LED OFF
Depends on charge mode
Low
Approximately
200ms
Power ON or Standby mode cancel
Figure 2. LEDN output
Quick Charge Termination
Quick charge finishes when either –∆V voltage is detected or the maximum charging time has elapsed.
NIPPON PRECISION CIRCUITS—6