BQ24735 Datasheet, PDF (18/42 Pages) Texas Instruments – 1-4 Cell Li+ Battery SMBus Charge Controller for Supporting Turbo Boost Mode with N-Channel Power MOSFET Selector

bq24735
SLUSAK9 – SEPTEMBER 2011
www.ti.com
Setting Charger Options
By writing ChargeOption() command (0x12H or 0b00010010), bq24735 allows users to change several charger
options after POR (Power On Reset) as shown in Table 3.
Table 3. Charge Options Register (0x12H)
BIT
[15]
[14:13]
[12:11]
[10]
[9]
[8]
[7]
[6]
[5]
[4]
[3]
[2]
[1]
BIT NAME
DESCRIPTION
ACOK Deglitch Time
Adjust
Adjust ACOK deglitch time.
After POR, the first time the adapter plug in occurs, deglitch time is always 150ms no matter if this bit is
0 or 1. This bit only sets the next ACOK deglitch time after ACFET turns off at least one time. To change
this option, VCC pin voltage must be above UVLO and ACDET pin voltage must be above 0.6V to
enable IC SMBus communication.
0: ACOK rising edge deglitch time 150ms
1: ACOK rising edge deglitch time 1.3s <default at POR>
WATCHDOG Timer
Adjust
Set maximum delay between consecutive SMBus Write charge voltage or charge current command. The
charge will be suspended if IC does not receive write charge voltage or write charge current command
within the watchdog time period and watchdog timer is enabled.
The charge will be resumed after receive write charge voltage or write charge current command when
watchdog timer expires and charge suspends. During boost function, the timer is fixed to 175s if it is
enabled.
00: Disable Watchdog Timer
01: Enabled, 44 sec
10: Enabled, 88 sec
11: Enable Watchdog Timer (175s) <default at POR>
BAT Depletion
Comparator
Threshold Adjust
This is used for LEARN function and boost mode function battery over discharge protection. During
LEARN cycle, when the IC detects battery voltage is below depletion voltage threshold, the IC turns off
BATFET and turned on ACFET to power the system from AC adapter instead of the battery. During
boost mode function, when the IC detects battery voltage is below depletion voltage threshold, IC stops
boost function. The rising edge hysteresis is 340mV. Set ChargeVoltage() register value to 0V will
disable this function.
00: Falling Threshold = 59.19% of voltage regulation limit (~2.486V/cell)
01: Falling Threshold = 62.65% of voltage regulation limit (~2.631V/cell)
10: Falling Threshold = 66.55% of voltage regulation limit (~2.795V/cell)
11: Falling Threshold = 70.97% of voltage regulation limit (~2.981V/cell) < default at POR>
EMI Switching
Frequency Adjust
0: Reduce PWM switching frequency by 18% <default at POR>
1: Increase PWM switching frequency by 18%
EMI Switching
Frequency Enable
0: Disable adjust PWM switching frequency <default at POR>
1: Enable adjust PWM switching frequency
IFAULT_HI
Comparator
Threshold Adjust
Short circuit protection high side MOSFET voltage drop comparator threshold.
0: function is disabled
1: 750mV <default at POR>
IFAULT_LOW
Comparator
Threshold Adjust
Short circuit protection low side MOSFET voltage drop comparator threshold. This is also used for
cycle-by-cycle current limit protection threshold during boost function.
0: 135mV <default at POR>
1: 230mV
LEARN Enable
Set this bit 1 start battery learn cycle. IC turns off ACFET and turns on BATFET to discharge battery
capacity. When battery voltage reaches threshold defined in bit [12;11], the BATFET is turned off and
ACFET is turned on to finish battery learn cycle. After finished learn cycle, this bit is automatically reset
to 0. Set this bit 0 will stop battery learn cycle. IC turns off BATFET and turns on ACFET.
0: Disable LEARN Cycle <default at POR>
1: Enable LEARN Cycle
IOUT Selection
0: IOUT is the 20x adapter current amplifier output <default at POR>
1: IOUT is the 20x charge current amplifier output
AC Adapter Indication 0: AC adapter is not present (ACDET < 2.4V) <default at POR>
(Read Only)
1: AC adapter is present (ACDET > 2.4V)
BOOST Enable
0: Disable Turbo BOOST function <default at POR>
1: Enable Turbo BOOST function
Boost Mode Indication 0: Charger is not in boost mode <default at POR>
(Read Only)
1: Charger is in boost mode
ACOC Threshold
Adjust
0: function is disabled
1: 3.33x of input current regulation limit <default at POR>
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