MAX1259CSLASHD datasheet(6/8 Pages) MAXIM

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To achieve rated performance, the VCC input should be

connected to both VCCI pins (pins 15 and 16). As well, the

switched output should be connected to both VCCO pins

(pins 12 and 13).

Power Fail

The power-fail (PF) output is high for VCCI greater than

1.26 x VBATT (VTP), indicating a valid VCCI voltage.

Battery Fail

If VCCI is at or above the voltage trip threshold (VTP) and

the backup battery is greater than 2V, the battery-fail (BF)

output will be held high, indicating a charged battery. If the

backup battery drops below 2V or VCCI falls below VTP,

BF will be driven low.

BAT Output

During normal operation, the BAT output stays at the bat-

tery voltage, regardless of the VCCI level. This provides

1mA battery current.

RESET (Digitally Controlled

Battery Disconnect)

To prevent battery discharge during shipping, the backup

battery can be disconnected from VCCO to BAT.

This disconnect feature is activated by pulsing the reset

(RST) input high for a minimum of 50ns with VCCI greater

than VTP (Figure 4). When primary power is removed,

the VCCO and BAT outputs will go high impedance. The

next time primary power is applied with VCCI greater than

1.26 x VBATT (VTP), normal operation resumes. Note that

when the MAX1259 is first powered up, VCCI must be

brought above 1.26 x VBATT. This resets an internal flip-

flop, ensuring that the part is in normal VCC mode and not

in shipping mode.

Applications Information

If a protection diode is placed in series with the backup

battery, pin 2 must be bypassed with at least a 0.01μF

capacitor to ground.

Figure 4. Reset Timing

+5V

VCCI

VCCO

RST

+5V

+3V

VIH

VIL

BAT

50ns MIN

HIGH IMPEDANCE

MAX1259

Battery Manager

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