LTC6804-1/LTC6804-2
55
680412fc
For more information www.linear.com/LTC6804-1
operaTion
Calculation of serial interface time for sequence above:
Number of LTC6804-1s in daisy chain stack = n
Number of bytes in sequence (B):
Command: 2 (command byte) + 2 (command PEC) = 4
Data: 6 (Data bytes) + 2 (Data PEC) per LTC6804 = 8
bytes per device
B = 4 + 8 • n
Serial port frequency per bit = F
Time = (1/F) • B • 8 bits/byte = (1/F) • [4 + 8 • n] • 8
Time for 3 LTC6804 example above, with 1MHz serial
port = (1/1e6) • (4 + 8 • 3) • 8 = 224µs
Note: This time will remain the same for all write and read
commands.
Read Cell Voltage Register Group A
1. Pull CSB low
2. Send RDCVA command (0x00 0x04) and its PEC (0x07
0xC2)
3. Read CVAR0 byte of device S1, then CVAR1(S1), …
CVAR5(S1), PEC of CVAR0(S1) to CVAR5(S1)
4. Read CVAR0 byte of device S2, then CVAR1(S2), …
CVAR5(S2), PEC of CVAR0(S2) to CVAR0(S2)
5. Read CVAR0 byte of device S3, then CVAR1(S3), …
CVAR5(S3), PEC of CVAR0(S3) to CVAR5(S3)
6. Pull CSB high
Start Cell Voltage ADC Conversion
(All cells, normal mode with discharge permitted) and
poll status
1. Pull CSB low
2. Send ADCV command with MD[1:0] = 10 and DCP = 1
i.e. 0x03 0x70 and its PEC (0xAF 0x42)
3. Pull CSB high
Clear Cell Voltage Registers
1. Pull CSB low
2. Send CLRCELL command (0x07 0x11) and its PEC
(0xC9 0xC0)
3. Pull CSB high
Poll ADC Status
(Parallel configuration and ISOMD = 0)
This example uses an addressed LTC6804-2 with address
A [3:0] = 0011 and ISOMD = 0
1. Pull CSB low
2. Send PLADC command (0x9F 0x14) and its PEC (0x1C
0x48 )
3. SDO output is pulled low if the LTC6804-2 is busy. The
host needs to send clocks on SCK in order for the poll
-
ing status to be updated from the addressed device.
4.
SDO output is high when the LTC6804-2 has completed
conversions
5. Pull CSB high to exit polling
Talk to an I
2
C Slave Connected to LTC6804
The LTC6804 supports I
2
C slave devices by connection to
GPIO4(SDA) and GPIO5(SCL). One valuable use for this
capability is to store production calibration constants or
other information in a small serial EEPROM using a con
-
nection like shown in Figure 25.
Figure 25. Connecting I
2
C EEPROM to LTC6804 GPIO Pins
GPIO5(SCL)
GPIO4(SDA)
4.7k
V
–
V
REG
LTC6804
1µF
10V
4.7k
WP
VCC
24AA01
SCL
VSS
SDA
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