BQ24700_14 Datasheet, PDF (11/32 Pages) Texas Instruments – NOTEBOOK PC BATTERY CHARGE CONTROLLER

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bq24700, bq24701
NOTEBOOK PC BATTERY CHARGE CONTROLLER
AND SELECTOR WITH DPM
SLUS452B – APRIL 2001 – REVISED NOVEMBER 2002
pin assignments (continued)
ACSET: Adapter current programming voltage. This input sets the system current level at which dynamic power
management occurs. Adapter currents above this programmed level activate the dynamic power management
and proportionally reduce the available power to the battery.
ALARM: Depleted battery alarm output. This open-drain pin indicates that a depleted battery condition exists.
A pullup on ALARM goes high when the voltage on the BATDEP pin is below 1.20 V. On the bq24700, the
ALARM output also activates when the selector inputs do not match the selector state.
BATDEP: Depleted battery level. A voltage divider network from the battery to BATDEP pin is used to set the
battery voltage level at which depletion is indicated by the ALARM pin. See ALARM pin for more details. A
battery depletion is detected when BATDEP is less than 1.2 V. A no-battery condition is detected when the
battery voltage is < 80% of the depleted threshold. In a no-battery condition, the bq24700 automatically selects
ac as the input source. If ENABLE = 1, the PWM remains enabled.
BATDRV: Battery power source select output. This pin drives an external P-channel MOSFET used to switch
the battery as the system’s power source. When the voltage level on the ACDET pin is less than 1.2 V, the output
of the BATDRV pin is driven low, GND. This pin is driven high (V_CC) when ACSEL is high and ACDET > 1.2 V.
BATP: Battery charge regulation voltage measurement input to the battery-voltage g_m amplifier. The voltage
on this pin is typically derived from a voltage divider network connected across the battery. In a voltage loop,
BATP is regulated to the 1.25 V, ±0.5% precision reference of the battery voltage g_m amplifier.
BATSET: An external override to an internal precision 0.5% reference. When BATSET is > 0.25 V, the voltage
level on the BATSET pin sets the voltage charge level. When BATSET ≤ 0.25 V, an internal 1.25-V, ±0.5%
reference is connected to the inverting input of the battery error amplifier. To ensure proper battery voltage
regulation with BATSET, BATSET must be > 1.0 V. Simply ground BATSET to use the internal reference.
COMP: The inverting input to the PWM comparator and output of the g_m amplifiers. A type II compensation
network between COMP and GND is recommended.
ENABLE: Charge enable. A high on this input pin allows PWM control operation to enable charging while a
low on this pin disables and forces the PWM output to a high state. Battery charging is initiated by asserting a
logic 1 on the ENABLE pin.
NOTE:The ENABLE pin should be asserted high only after ACDET has been asserted high and
V_REF has been established. When ac is lost, and the bq24700/bq24701 drives ACPRES low, the
host must assert the ENABLE low.
GND: Supply return and ground reference
IBAT: Battery current differential amplifier output. The output of this pin produces a voltage proportional to the
battery charge current. This voltage is suitable for driving an ADC input.
PWM: Gate drive output pin drives the P-channel MOSFET for PWM control. The PWM control is active when
ACPRES, ACSEL, and ENABLE are high. PWM is driven low to V_HSP and high to V_CC.
SRN, SRP: Differential amplifier inputs for battery current sense. These pins feed back the battery charge
current for PWM control. SRN is tied to the battery terminal. Care must be taken to keep SRN and SRP below
their absolute maximum rating, especially when the battery is removed. Refer to the application section, under
ACDET operation, for further detail outlining the various connection configurations which help keep SRN and
SRP within safe operating regions.
SRSET: Battery charge current programmed voltage. The level on this pin sets the battery charge current limit.
VCC: Operational supply voltage.
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