LTC6802-1 Datasheet, PDF (23/32 Pages) Linear Technology – Multicell Battery Stack Monitor

LTC6802-1
APPLICATIONS INFORMATION
SERIAL COMMAND EXAMPLES
LTC6802-1 (Daisy Chained Configuration)
Examples below use a configuration of three stacked
devices: bottom (B), middle (M), and top (T)
Write Configuration Registers
1. Pull CSBI low
2. Send WRCFG command byte
3. Send CFGR0 byte for top device, then CFGR1 (T), CFGR2 (T), … CFGR5 (T)
4. Send CFGR0 byte for middle device, then CFGR1 (M), CFGR2 (M), … CFGR5 (M)
5. Send CFGR0 byte for bottom device, then CFGR1 (B), CFGR2 (B), … CFGR5 (B)
6. Pull CSBI high; data latched into all devices on rising edge of CSBI
Calculation of serial interface time for sequence above:
Number of devices in stack= N
Number of bytes in sequence = B = 1 command byte and 6 data bytes per device = 1+6*N
Serial port frequency per bit = F
Time = (1/F) * B * 8 bits/byte = (1/F) * (1+6*N) * 8
Time for 3-cell example above, with 1MHz serial port = (1/1000000) * (1+6*3)*8 = 152us
Read Cell Voltage Registers (12 Cell Mode)
1. Pull CSBI low
2. Send RDCV command byte
3. Read CVR00 byte of bottom device, then CVR01 (B), CVR02 (B), … CVR17 (B), and then PEC (B)
4. Read CVR00 byte of middle device, then CVR01 (M), CVR02 (M), … CVR17 (M), and then PEC (M)
5. Read CVR00 byte for top device, then CVR01 (T), CVR02 (T), … CVR17 (T), and then PEC (T)
6. Pull CSBI high
Calculation of serial interface time for sequence above:
Number of devices in stack= N
Number of bytes in sequence = B = 1 command byte, and 18 data bytes plus 1 PEC byte per device = 1+19*N
Serial port frequency per bit = F
Time = (1/F) * B * 8 bits/byte = (1/F) * (1+19*N) * 8
Time for 3-cell example above, with 1MHz serial port = (1/1000000) * (1+19*3)*8 =464us
Start Cell Voltage A/D Conversions and Poll Status (Toggle Polling)
1. Pull CSBI low
2. Send STCVAD command byte (all devices in stack start A/D conversions simultaneously)
3. SDO output from bottom device pulled low for approximately 12ms
4. SDO output toggles at 1kHz rate, indicating conversions complete for all devices in daisy chain
5. Pull CSBI high to exit polling
68021p
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