Datasheet

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FUNCTIONAL DESCRIPTION
OSCILLATOR FUNCTION
bq2084-V143
SLUS732 – SEPTEMBER 2006
Terminal Functions
TERMINAL
I/O DESCRIPTION
NO. NO.
NAME
TSSOP QFN
DISP 17 2 I Display control for the LED drivers LED1 through LED5
CLKOUT 35 20 O 32.768-kHz output to the bq29312
FILT 32 17 I Analog input connected to the external PLL filter
EVENT 25 10 I Input from bq29312 XALERT output
LED1 24 9 O
LED2 23 8 O
LED3 22 7 O LED display segments that each may drive an external LED
LED4 21 6 O
LED5 20 5 O
MRST 26 11 I Master reset input that forces the device into reset when held high
7, 13, 14, 36,
NC 21, 29, 35 – No connection
37
PFIN 18 3 I Active low input to detect secondary protector output status
PRES 5 27 I Active low input to sense system insertion
PU 4 26 O Output to pull up the PRES pin for detection
Register backup that provides backup potential to the bq2084-V143 data
RBI 9 31 I registers during periods of low operating voltage. RBI accepts a storage
capacitor or a battery input.
SAFE 12 34 O Active low output for additional level of safety protection; e.g., fuse blow.
SCLK 6 28 O Communication clock to the bq29312
SDATA 10 32 I/O Data transfer to and from bq29312
SMBus clock open-drain bidirectional pin used to clock the data transfer to and
SMBC 15 36 I/O
from the bq2084-V143
SMBus data open-drain bidirectional pin used to transfer address and data to
SMBD 16 1 I/O
and from the bq2084-V143
SR1 28 13 I
Connections for a small-value sense resistor to monitor the battery charge- and
discharge-current flow
SR2 27 12 I
TS 2 24 I Thermistor voltage input connection to monitor temperature
VDDA 31 16 I Positive supply for analog circuitry
VDDD 8 30 I Positive supply for digital circuitry and I/O pins
VIN 1 25 I Single-cell voltage input from the bq29312
VSSA 3, 29, 30 14, 15 I Negative supply for analog circuitry
VSSD 11, 19, 38 4, 22, 23, 33 I Negative supply for digital circuitry
XCK1/VSSA 34 19 I 32.768-kHz crystal oscillator input pin or connected to VSSA if the internal
oscillator is used
32.768-kHz crystal oscillator output pin or connected to a 100-k Ω , 50 ppm or
XCK2/ROSC 33 18 O
better resistor if the internal oscillator is used
The oscillator of the bq2084-V143 can be set up for an internal or external operation. As the bq2084-V143
powers up it automatically attempts to start the internal oscillator, but if a 100-k Ω resistor is not connected to
ROSC (pin 33), then it attempts to start the oscillator using an external 32.768-kHz crystal. Either the 100-k Ω
ROSC resistor OR the 12 pF 32.768-kHz crystal should be mounted, NOT both.
The performance of the internal oscillator depends on the tolerance of the 100-k Ω resistor connected between
7
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