MAX781CBX 데이터 시트보기 (PDF) - Maxim Integrated
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MAX781CBX Datasheet PDF : 24 Pages
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PDA/Hand-Held Computer Power Controller
The 3VSTAT comparator is disabled in the low-power,
standby, and shutdown modes, and outputs a logic
zero regardless of the state of its inputs. The MAX781
serial-interface outputs are powered from 3OUT. If
3OUT is short circuited to ground, then neither DOUT
nor INT will be able to source current.
CHGINT and CHGSTAT indicate the status of the
charging voltage applied to VCHG. The MAX781 pow-
ers itself from either BATT or VCHG, whichever has the
higher voltage. CHGSTAT = 0 when BATT is approxi-
mately 200mV greater than VCHG. CHGSTAT = 1
when BATT falls below VCHG plus approximately
200mV. Any transition on CHGSTAT sets CHGINT.
The CHGSTAT comparator is disabled only in shut-
down mode.
At power-up, BATTINT is set if the charger is not con-
nected, CHGINT is set if the charger is connected.
Table 4. Status Detection in the Four Operating
Modes
STATUS
BIT
Shutdown
BATTSTAT
3VSTAT
CHGSTAT
Disabled
Disabled
Disabled
MODE
Low
Power
Disabled
Disabled
Enabled
Standby
Enabled
Enabled
Enabled
Operate
Enabled
Enabled
Enabled
The INT pin outputs the logical OR of the BATTINT,
3VINT, and CHGINT status bits. The INT pin generates
an interrupt on the CPU that controls the MAX781.
Supply and Reference
5OUT outputs +5V, linear regulated from either BATT or
VCHG, in all modes except shutdown. 5OUT can
source up to 25mA. Power comes from BATT as long
as the BATT voltage is greater than the VCHG voltage.
When the VCHG voltage exceeds BATT, VCHG sup-
plies the 5OUT linear regulator.
The MAX781’s internal circuitry is powered from 5OUT.
When the DLO pin drives high, it sources current from
5OUT. The DOUT and INT pin output drivers are pow-
ered from 3OUT. If an external 5V supply is available
and connected to the 5OUT pin, the 5OUT linear regu-
lator can be disabled by clearing the 5ON bit. If 5ON is
cleared without an external +5V supply connected to
5OUT, or if 5OUT is shorted to ground, the MAX781
internal registers will be cleared to their power-on state.
3.3V Output
3OUT outputs +3.3V in all modes except for shutdown.
In low-power and standby modes, 3OUT is linear regu-
lated from either BATT or VCHG, whichever has the
higher voltage. In operate mode, the switch-mode
buck (step-down) converter is activated to regulate
3OUT to 3.3V. In operate mode, the 3OUT linear regu-
lator is off.
BATTERY
PACK
BATT+
THERM
R8
RTEMP
T
BATT
3OUT
83k
TEMP
TO ANALOG MULTIPLEXER
COMPARATOR DISABLED IN
LOW-POWER MODE; OUTPUTS "0"
REGARDLESS OF STATE OF INPUTS
WRITING A "1" TO BATTINT
CLEARS THE FLIP FLOP
CLR
DQ
>
>
BATTINT
BATTSTAT
BATT-
R4
1µF
14.1k
AGND,
402k
PGND
MAX781
Figure 6. BATTINT, BATTSTAT Status Circuitry
______________________________________________________________________________________ 13
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