MAX1538 Datasheet, PDF (9/22 Pages) Maxim Integrated Products – Power-Source Selector for Dual-Battery Systems

Power-Source Selector for
Dual-Battery Systems
Typical Operating Characteristics (continued)
(Circuit of Figure 1. T_A = +25°C, unless otherwise noted.)
BREAK-BEFORE-MAKE TIMING
MAX1538 toc11
t_TRANS
MOSFET
TURN-OFF
TIME _MOSFET
TURN-ON
TIME
MOSFET FOR INITIAL
DISCHARGE PATH
MOSFET FOR FINAL
DISCHARGE PATH
1.00µs/div
16V
14V
12V ^MOSFET
DRIVERS
10V
8V
FIRST SOURCE INSERTION
5V ^{MAX1538 toc12}
0V
OUT1
OUT2, OUT0
POWER-UP TIME
200µs/div
20V VADPIN
10V VREVBLK
0V
20V
V_EXTLD
10V
0V
Pin Description
PIN
NAME
FUNCTION
1
MINVA ^{Minimum Battery A Voltage Set Point. Battery A discharge is prevented if VBATA has fallen below 5 x}
V_MINVA.
2
MINVB ^{Minimum Battery B Voltage Set Point. Battery B discharge is prevented if VBATB has fallen below 5 x}
V_MINVB.
3
BATSEL
Battery-Selection Input. Drive to logic low to charge battery A or give discharge preference to battery A.
Drive to logic high to charge battery B or give discharge preference to battery B.
4
RELRN Battery-Relearn Logic-Level Input. Drive RELRN high to enable battery-relearn mode.
5
CHRG ^{Charge-Enable Logic-Level Input. Drive CHRG high to enable the charging path from the charger to the}
battery selected by BATSEL.
6
OUT0
7
OUT1
Selector-State Output. This open-drain output indicates the state of the MAX1538. See Table 1 for
information on decoding.
8
OUT2
9
ACDET
AC-Adapter Detection Input. When V_ACDET is greater than the ACDET trip threshold (2V typ), adapter
presence is detected.
10
AIRDET
Airline-Adapter Detection Input. When V_AIRDET > 2V and V_ACDET < 2V, the airline-adapter presence is
detected. Charging is disabled when an airline adapter is detected.
11
ADPIN ^{Adapter Input. When VADPIN > VBATSUP, the MAX1538 is powered by ADPIN. ADPIN is the supply rail for}
the ADPPWR MOSFET driver.
Adapter-Power P-Channel MOSFET Driver. Connect ADPPWR to the gate of P1 (Figure 1). P1 disconnects
12
ADPPWR
the adapter from the system during relearn mode. Exclude P1 and leave ADPPWR disconnected if relearn
is not used. ADPPWR is driven relative to ADPIN. ADPPWR and REVBLK are driven with the same control
signal.
Gate Drive for the Reverse-Blocking P-Channel MOSFET. Connect REVBLK to the gate of P2 (Figure 1). P2
13
REVBLK enables and disables the AC adapter’s power path. REVBLK is driven relative to EXTLD. REVBLK and
ADPPWR are driven with the same control signal.
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