BQ29311_15 Datasheet, PDF (12/24 Pages) Texas Instruments – FOUR-CELL LITHIUM-ION

Not Recommended for New Designs
bq29311
SLUS487D − DECEMBER 2001 − REVISED NOVEMBER 2003
www.ti.com
THERMISTOR DRIVE CIRCUIT
The TOUT pin can be enabled to drive a thermistor from
VREG. The typical thermistor resistance is 10 kΩ at 25°C.
The default-state for this is OFF to conserve power. The
maximum output impedance is 100 Ω. TOUT (b6 of the
control register) enables or disables this function. TOUT
(b6 of CONTROL register) enables or disables this
feature.
LED DRIVE CIRCUIT
The LED drive provides a current source from VREG.
LEDEN (b5 of the control register) enables or disables this
function.
CONTROL INPUT (CNTL)
The control input is pulled up internally to VREG, which
disables all the FET outputs. When CNTL is pulled to
GND, the bq29311 control outputs are then controlled by
safety and register control logic. An external pullup can be
added to enable a pullup to a higher voltage. This could
cause up to an extra 100 µA leakage through the CNTL
input to GND.
CLOCK INPUT (CLKIN)
The clock input allows for an external time base to be used
for increased accuracy in delay timing when determining
overcurrent and short-circuit holdoff. The standard
frequency is 32.768 kHz but must be above 30 kHz. This
input is pulled up via an internal 100-kΩ resistor.
Transitions of the CLKIN pin hold off the internal oscillator
so if the external input stops oscillating, the internal
oscillator starts and enables all the timing functions.
COMMUNICATIONS
The I²C compatible serial communications provides read
and write access to the bq29311 data area. The data is
clocked via separate data (SDATA) and clock (SCLK) pins.
The bq29311 acts as a slave device and does not generate
clock pulses. Communication to the bq29311 can be
provided from GPIO pins or an I²C supporting port of a host
system controller. The slave address for the bq29311 is 7
bits and the value is 0100 000 (0x20).
ADDRESS (0X20)
6
5
4
3
2
1
0
0
1
0
0
0
0
0
The bq29311 does not have the following functions
compatible with the I²C specification.
D The bq29311 is always regarded as a slave.
D The bq29311 does not support the general code of the
I²C specification and therefore does not return an
ACK, but returns a NACK instead.
D The bq29311 does not support the address auto
increment, which allows continuous reading and
writing.
D The bq29311 allows data to be written or read from the
same location without resending the location address.
SCLK
SDATA
A6 A5 A4 A0 R/W ACK
Start
0
0
Slave Address
R7 R6 R5
R0 ACK
0
Register Address
D7 D6 D5
D0 ACK
0
Data
NOTE: _{Slave = bq29311}
Figure 4. I²C-Bus Write to bq29311
SCLK
SDATA
A6 A5 A0 R/W ACK R7 R6
R0 ACK
A6
A0 R/W ACK D7 D6
D0 NACK
Start
00
Slave Address
NOTE: _{Slave = bq29311}
Register
Address
10
Slave Address
Slave
Drives
The Data
Master
Drives
NACK
and Stop
Stop
Figure 5. I²C-Bus Read from bq29311: Protocol A
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