Stand-Alone, Switch-Mode
Li+ Battery Charger with Internal 28V Switch
MAX1758
Table 1. Charging State Table
STATE
ENTRY CONDITIONS
From initial power-on
or
from done state if battery voltage < recharge volt-
age threshold
or
V
DCIN
- V
BATT
< dropout threshold
or
V
BATT
> battery overvoltage threshold
STATE CONDITIONS
Reset
Timers reset, charging current = 0,
FASTCHG
= high,
FULLCHG
= high,
FAULT
= high
Prequalification
From reset state if input power, reference, and inter-
nal bias are within limits
Battery voltage
≤
undervoltage threshold,
charging current = (fast-charge current / 10),
timeout = 7.5min typ (C
TIMER1
= 1nF),
FASTCHG
= low,
FULLCHG
= high,
FAULT
= high
Undervoltage threshold
≤
battery voltage
≤
battery regulation voltage,
charging current = charge current limit,
timeout = 90min typ (C
TIMER2
= 1nF),
FASTCHG
= low,
FULLCHG
= high,
FAULT
= high
Battery voltage = battery regulation voltage,
charging current
≤
current limit,
timeout = 90min typ (C
TIMER1
= 1nF),
FASTCHG
= high,
FULLCHG
= low,
FAULT
= high
Battery voltage = battery regulation voltage,
charging current
≤
330mA,
timeout = 45min typ
(C
TIMER1
= 1nF),
FASTCHG
= high,
FULLCHG
= high,
FAULT
= high
Recharge voltage threshold
≤
battery,
voltage
≤
voltage limit, charging current = 0,
FASTCHG
= high,
FULLCHG
= high,
FAULT
= high
Charge current = 0, timers suspended,
FASTCHG
= no change,
FULLCHG
= no change,
FAULT
= no change
Fast Charge
(Constant Current)
From prequalification state if battery voltage >
undervoltage threshold
Full Charge
(Constant Voltage)
From fast-charge state if battery voltage = battery
regulation voltage
Top-Off
(Constant Voltage)
From full-charge state if full-charge timer expires
or
if charging current
≤
330mA
Done
From top-off state if top-off timer expires
Over/Undertemperature
From fast-charge state or full-charge state if battery
temperature is outside limits
From reset state if battery temperature
≥
maximum
battery temperature
or
from prequalification state if prequalification timer
expires
or
from fast-charge state if fast-charge timer expires
Fault
Charging current = 0,
FASTCHG
= high,
FULLCHG
= high,
FAULT
= low
10
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