BQ25895_16 Datasheet, PDF (27/67 Pages) Texas Instruments – Adjustable Voltage 3.1-A Boost Operation

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bq25895
SLUSC88A – MARCH 2015 – REVISED MAY 2016
2. Clear BATFET_DIS bit
3. Set REG_RST bit to reset all registers including BATFET_DIS bit to default (0)
4. A logic high to low transition on QON pin with t_SHIPMODE deglitch time to enable BATFET to exit shipping
mode
8.2.10.3 BATFET Full System Reset
The BATFET functions as a load switch between battery and system when input source is not plugged-in. By
changing the state of BATFET from off to on, system connects to SYS can be effectively have a power-on-reset.
The QON pin supports push-button interface to reset system power without host by change the state of BATFET.
When the QON pin is driven to logic low for t_{QON_RST} (typical 15 seconds) while input source is not plugged in
and BATFET is enabled (BATFET_DIS=0), the BATFET is turned off for t_{BATFET_RST} and then it is re-enabled to
reset system power. This function can be disabled by setting BATFET_RST_EN bit to 0.
8.2.11 Current Pulse Control Protocol
The device provides the control to generate the VBUS current pulse protocol to communicate with adjustable
high voltage adapter in order to signal adapter to increase or decrease output voltage. To enable the interface,
the EN_PUMPX bit must be set. Then the host can select the increase/decrease voltage pulse by setting one of
the PUMPX_UP or PUMPX_DN bit (but not both) to start the VBUS current pulse sequence. During the current
pulse sequence, the PUMPX_UP and PUMPX_DN bits are set to indicate pulse sequence is in progress and the
device pulses the input current limit between current limit set forth by IINLIM or IDPM_LIM register and the
100mA current limit (I_{INDPM100_ACC}). When the pulse sequence is completed, the input current limit is returned to
value set by IINLIM or IDPM_LIM register and the PUMPX_UP or PUMPX_DN bit is cleared. In addition, the
EN_PUMPX can be cleared during the current pulse sequence to terminate the sequence and force charger to
return to input current limit as set forth by the IINLIM or IDPM_LIM register immediately. When EN_PUMPX bit is
low, write to PUMPX_UP and PUMPX_DN bit would be ignored and have no effect on VBUS current limit.
8.2.12 Input Current Limit on ILIM
For safe operation, the device has an additional hardware pin on ILIM to limit maximum input current on ILIM pin.
The input maximum current is set by a resistor from ILIM pin to ground as:
I_INMAX
=
K_ILIM
R_ILIM
(3)
The actual input current limit is the lower value between ILIM setting and register setting (IINLIM). For example, if
the register setting is 111111 for 3.25 A, and ILIM has a 260-Ω resistor (KILIM = 390 max.) to ground for 1.5 A,
the input current limit is 1.5 A. ILIM pin can be used to set the input current limit rather than the register settings
when EN_ILIM bit is set. The device regulates ILIM pin at 0.8 V. If ILIM voltage exceeds 0.8 V, the device enters
input current regulation (Refer to Dynamic Power Management section).
The ILIM pin can also be used to monitor input current when EN_ILIM is enabled. The voltage on ILIM pin is
proportional to the input current. ILIM pin can be used to monitor the input current following Equation 4:
I_IN
=
K_ILIM
R_ILIM
x
x
V_ILIM
0.8 V
(4)
For example, if ILIM pin is set with 260-Ω resistor, and the ILIM voltage is 0.4 V, the actual input current 0.615 A
- 0.75 A (based on KILM specified). If ILIM pin is open, the input current is limited to zero since ILIM voltage
floats above 0.8 V. If ILIM pin is short, the input current limit is set by the register.
The ILIM pin function can be disabled by setting EN_ILIM bit to 0. When the pin is disabled, both input current
limit function and monitoring function are not available.
8.2.13 Thermal Regulation and Thermal Shutdown
8.2.13.0.1 Thermal Protection in Buck Mode
The device monitors the internal junction temperature T_J to avoid overheat the chip and limits the IC surface
temperature in buck mode. When the internal junction temperature exceeds the preset thermal regulation limit
(TREG bits), the device lowers down the charge current. The wide thermal regulation range from 60ºC to 120ºC
allows the user to optimize the system thermal performance.
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