BQ24702_16 Datasheet, PDF (13/37 Pages) Texas Instruments – MULTICHEMISTRY BATTERY CHARGER CONTROLLER

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bq24702
bq24703
SLUS553E – MAY 2003 – REVISED OCTOBER 2007
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 V_ACPRES. On the bq24702, 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 V_ACPRES. A no-battery condition is detected when the
battery voltage is < 80% of the depleted threshold. In a no-battery condition, the bq24702 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 V_ACPRES, the output
of the BATDRV pin is driven low, GND. This pin is driven high (V_CC) when ACSEL is high and ACDET > V_ACPRES.
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 V_FB precision reference of the battery voltage g_m amplifier.
BATSET: An external override to an internal precision 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 V_FB 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.
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. SRP is the source pin for zero volt operation.
SRSET: Battery charge current programmed voltage. The level on this pin sets the battery charge current limit.
VCC: Operational supply voltage.
VHSP: The VHSP pin is connected to a 1-μF capacitor (close to the pin) to provide a stable voltage source to
drive the gates of the external MOSFETs. VHSP = VCC – 10 V for VCC > 10.5 V and VHSP = VCC – 0.5 V for
VCC <10.5 V. A 13-V Zener diode should be placed between VCC and VHSP to prevent MOSFET overstress
during start-up.
VREF: Bypassed precision voltage 5-V output. It can be used to set fixed levels on the inverting inputs of any
one of the three error amplifiers if desired. The tight tolerance is suitable for charging lithium-ion batteries.
VS: System (Load) voltage input pin. The voltage on this pin indicates the system voltage in order to insure a
break before make transition when changing from ac power to battery power. The battery is protected from an
over-voltage condition by disabling the P-channel MOSFET connected to the BATDRV pin if the voltage at VS is
greater than BATP. This function can be eliminated by grounding the VS pin.
Copyright © 2003–2007, Texas Instruments Incorporated
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Product Folder Link(s): bq24702 bq24703