DS1259 Datasheet, PDF (2/5 Pages) Dallas Semiconductor – Battery Manager Chip

DS1259
OPERATION
During normal operation, V_CCI (Pins 15 and 16) is the primary energy source and power is supplied to
V_CCO (Pins 12 and 13) through an internal switch at a voltage level of V_CCI-0.2 volts at 250 mA. During
this time the power-fail signal ( PF ) is held high, indicating valid V_CCI voltage (see Figure 1). However, if
the V_CCI falls below the trip point (V_TP), a level of 1.26 times the battery level (V_BAT), the power-fail
signal is driven low. As V_CCI falls below the battery level, power is switched from V_CCI to V_BAT and the
battery supplies power to the uninterruptible output (V_CCO) at V_BAT-0.2 volts at 15 mA.
On power-up, as the V_CCI supply rises above the battery, the primary energy source, V_CCI, becomes the
supply. As V_CCI rises above the trip point (V_TP), the power fail signal is driven back to the high level.
During normal operation, BAT (Pin 5) stays at the battery level regardless of the level of V_CCI.
BATTERY FAIL
When power is being supplied from the primary energy source, BF (Pin 3) is held at a high level,
provided that the attached battery (V_BAT) is greater than 2 volts. If the battery level should decrease to
below 2 volts, the BF signal is driven low, indicating a low battery. The BF signal is always low when
the PF signal is low.
RESET
The reset input can be used to prevent the battery from supplying power to V_CCO and BAT even if V_CCI
falls below the level of the battery. This feature is activated by applying a pulsed input on RST to high
level for 50ns minimum while primary power is valid (see Figure 2). When primary power is removed
after pulsing RST, the V_CCO output and BAT will go to high impedance. The next time primary power is
applied such that V_CCI is greater than V_BAT, normal operation resumes and V_CCO will be supplied by the
battery or V_CCI. The BAT output will also return to the level of the battery. Figure 3 shows the DS1259 in
a typical application.
BLOCK DIAGRAM Figure 1
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