BQ24721 Datasheet, PDF (36/48 Pages) Texas Instruments – ADVANCED MULTI-CHEMISTRY AND MULTI-CELL SYNCHRONOUS SWITCH-MODE CHARGER AND SYSTEM POWER SELECTOR

bq24721
SLUS683 – NOVEMBER 2005
www.ti.com
PROGRAMMED VOLTAGE VALUE DIFFERENCE BETWEEN Li-Ion AND NiMH BATTERY PACK
CHARGING
• Li-Ion based battery packs require both current regulation and voltage regulation loops – where
constant-current and constant voltage is needed to fully charge the battery pack.
• NiMH batteries require only a constant current for charging. Thereby, the voltage regulation loop is not
needed. To accomplish this, set the regulation voltage at a value greater than the maximum battery pack
voltage. This will not allow the voltage regulation loop to become active. The maximum value of 19.2 V could
be set for most NiMH battery packs.
SBS-Like SMBus: Commands Implemented: Control Register
Charger Mode, (0x12), Write-Only [Default POR and Reset Value in BOLD TYPE]
BIT
SBS SPEC
0 (LSB) INHIBIT CHARGE
1
ENABLE POLLING
2
POR_RESET
3
RESET_TO_ZERO
4
RESERVED
5
RESERVED
6
RESERVED
7
RESERVED
8
RESERVED
9
RESERVED
10
RESERVED
11
RESERVED
12
RESERVED
13–15(MSB) RESERVED
bq24721 SBS-Like
END CHARGE ⁽¹⁾
1: Disable Charger
0: Enable Charger
This affects STATUS register 0x13, bit 1.
RESERVED: Not Used. Bit always resets to zero.
RESET: (Return to POR values) Charger disabled, DPM active, PWM at 300 kHz, Vout = 0,
CHARGE CURR = 0, IDPM = 0
1: Reset
0: No Reset
IOUT Select: Current Sense Amplifier Output select
1: Charge current is the 20x amplifier output at IOUT pin
0: Adapter current is the 20x amplifier output at IOUT pin
The IOUT pin is multiplexed to either the charge current or the input current sense amplifiers. The
Input current (ac) is the default upon power up.
LEARN CYCLE
1: Connect Battery to system (learn cycle) even when adapter connected
0: Connect AC adapter to system (no learn) when adapter connected
This bit affects STATUS register 0x13, bits 6 and 7.
PWM FS: Switching Frequency Select
1: PWM at 500 kHz
0: PWM at 300 kHz
ACOC – AC (adapter) Over-Current
1: ACOC protection enabled
0: ACOC protection disabled
SET_ACOC <1:0>
00: ACOC=DPM × 1.3
01: ACOC=DPM × 1.5
10: ACOC=DPM × 1.7
11: ACOC=DPM × 1.9
Bit 6 of this Control register 0×12 needs to be high for these bits to take effect.
ACOC threshold is a percentage of the DPM (input current) regulation threshold programmed by
the DPM register 0×3F.
SET_BAT_DEPL <2:0> Battery depleted threshold
Value set per cell
000: [2.2V], 001:[2.3V], 010:[2.4V], 011:[2.5V]
100:[2.6V], 101:[2.7V], 110:[2.8V], 111:[2.9V]
These bits affect STATUS register 0×13, bits 11, 6 and 7.
RESERVED: Not Used. Bit always resets to zero.
RESERVED: Not Used. Bit always resets to zero.
(1) END_CHARGE bit must be LO AND the CHRGEN pin must be LO to enable the charger. If the END_CHARGE bit is HI or the
CHRGEN pin is HI, then the charger is disabled.
36