Datasheet

10
LTC1325
Bit 1: Start Bit (Start)
The first “logical one” clocked into the D
IN
input after CS
goes low is the start bit. The start bit initiates the data
transfer and all leading zeros which precede this logical
one will be ignored. After the start bit is received, the
remaining bits of the command word will be clocked in.
Bits 2 and 3: Mode Select (MOD0 and MOD1)
The two mode bits determine which of four modes the chip
will be in: idle, discharge, charge or gas gauge.
MOD1 MOD0 DESCRIPTION
0 0 Idle
0 1 Discharge
1 0 Charge
1 1 Gas Gauge
Bit 4: Single-Ended Differential Conversion (SGL/DIFF)
SGL/DIFF determines whether the ADC makes a single-
ended measurement with respect to ground or a differen-
tial measurement with respect to the Sense pin.
SGL/DIFF DESCRIPTION
0 Single-Ended ADC Conversion
1 Differential ADC Conversion (with respect to Sense)
COMMAND WORD
The command word is 22 bits long and contains all the
information needed to configure and control the chip. On
power-up all bits are cleared to logical “0.”
FUNCTIONAL DESCRIPTIO
UU
U
START
= 1
1
MOD0
2
MOD1
3
SGL/
DIFF
4
MSBF
5
DS0
6
DS1
7
DS2
8
DIV0
9
DIV1
10
DIV2
11
DIV3
12
PS
13
DR0
14
DR1
15
DR2
16
FSCLR
17
TO0
18
TO1
19
TO2
20
VR0
21
VR1
22
LTC1325 • F01
Figure 1. Command Word
Bit 5: MSB-First/LSB-First (MSBF)
The ADC data is programmed for MSB-first or LSB-first
sequence using the MSBF bit. See Serial I/O description
for details.
MSBF DESCRIPTION
0 LSB-First Data Follows MSB-First Data
1 MSB-First Data Only
Bits 6 to 8: ADC Data Input Select (DS0 to DS2)
DS2, DS1 and DS0 select which circuit is connected to the
ADC input. Do not use unlisted combinations.
DS2 DS1 DS0 DESCRIPTION
0 0 0 Gas Gauge Output
0 0 1 Battery Temperature Pin, T
BAT
0 1 0 Ambient Temperature Pin, T
AMB
0 1 1 Battery Divider Output Voltage, V
CELL
100V
IN
Pin
Bits 9 to 12: Battery Divider Ratio Select (DIV0 to DIV3)
DIV3, DIV2, DIV1 and DIV0 select the division ratio for the
voltage divider across the battery.
DIV3 DIV2 DIV1 DIV0 DESCRIPTION
0000(V
BAT
– V
SENSE
)/1
0001(V
BAT
– V
SENSE
)/2
0010(V
BAT
– V
SENSE
)/3
0011(V
BAT
– V
SENSE
)/4
0100(V
BAT
– V
SENSE
)/5
0101(V
BAT
– V
SENSE
)/6
0110(V
BAT
– V
SENSE
)/7
0111(V
BAT
– V
SENSE
)/8
1000(V
BAT
– V
SENSE
)/9
1001(V
BAT
– V
SENSE
)/10
1010(V
BAT
– V
SENSE
)/11
1011(V
BAT
– V
SENSE
)/12
1100(V
BAT
– V
SENSE
)/13
1101(V
BAT
– V
SENSE
)/14
1110(V
BAT
– V
SENSE
)/15
1111(V
BAT
– V
SENSE
)/16