ISL78610 Datasheet, PDF (80/98 Pages) Intersil Corporation – Multi-Cell Li-Ion Battery Manager

ISL78610
Cell Balancing – Timed Mode
Refer to “Timed Balance Mode” on page 47.
EXAMPLE: ACTIVATE BALANCING ON CELLS 2 AND 8
FOR 1 MINUTE.
Step 1. Write Balance Setup register: Set Timed Balance mode,
Balance Status pointer, and turn off balance.
BMD = 10 (Timed Balance mode)
BWT = XXX
BSP = 0000 (Balance Status Pointer location 0)
BEN = 0 (BALANCING disabled)
TABLE 53. BALANCE SETUP REGISTER
R/W PAGE ADDRESS
DATA
1
010
010011
XX XX00 000X XX10
X = don’t care
Step 2. Write Balance Status register: Set bits 1 and 7
BAL12:1 = 0000 1000 0010
TABLE 54. BALANCE STATUS REGISTER
R/W PAGE ADDRESS
DATA
1
010
010100
XX 0000 1000 0010
Step 3. Write balance timeout setting to the Watchdog/Balance
Time register (page 2, address 6’h15, bits [13:7])
BTM6:1 = 0000011 (1 minute)
TABLE 55. WATCHDOG/BALANCE TIME REGISTER
R/W PAGE ADDRESS
DATA
1
010
010101
00 0001 1XXX XXXX
X = don’t care – the lower bits are the watchdog timeout value and
should be set to a time longer than the balance time. A value of 111
1111 is suggested.
Step 4. Enable balancing using Balance Enable command
TABLE 56. BALANCE ENABLE COMMAND
R/W PAGE ADDRESS
DATA
0
011 010000
00 0000
Or enable balancing by setting BEN directly in the Balance Setup
register:
BEN = 1
TABLE 57. BALANCE SETUP REGISTER
R/W PAGE ADDRESS
DATA
1
010
010011
XX XX1X XXXX XXXX
The balance FETs attached to cells 2 and 8 turn on. The FETs turn
off after 1 minute. Balancing may be stopped by resetting BEN or
by sending the Balance Inhibit command.
Cell Balancing – Auto Mode
Refer to “Auto Balance Mode” on page 47.
BALANCE VALUE CALCULATION EXAMPLE
This example is based on a cell State of Charge (SOC) of 9360
coulombs, a target SOC of 8890 coulombs, a balancing leg
impedance of 31Ω (30Ω resistor plus 1Ω FET on resistance) and a
sampling time interval of 5 minutes (300 seconds).
The Balance Value is calculated using Equation 10.
B = ⁸----¹--₅-⁹---¹--  9360 – 8890  ₃--³--₀-¹--₀-- = 79562 = 28h00136CA
(EQ. 10)
The value 8191/5 is the scaling factor of the cell voltage
measurement.
The value of 28’h00136CA is loaded to the required Cell Balance
Register and the value 7’b0001111 (5 minutes) is loaded to the
Balance Time bits in the Watchdog/Balance time register.
In this example, the total coulomb difference to be balanced is:
470 coulomb (9360 - 8890). At 3.3V/31Ω * 300s = 31.9
coulomb per cycle, it takes about 15 cycles for the balancing to
terminate.
AUTO BALANCE MODE CELL BALANCING EXAMPLE
The following describes a simple setup to demonstrate the Auto
Balance mode cell balancing function of the ISL78610. Note that
this balancing setup is not related to the balance value
calculation in Equation 10.
Auto balance cells using the following criteria:
• Balance time = 20 seconds
• Balance wait time (dead time between balancing cycles) = 8
seconds
• Balancing disabled during cell measurements.
• Balance Values: See Table 58
TABLE 58. CELL BALANCE VALUES (HEX) FOR EACH CELL
CELL CELL CELL CELL CELL CELL CELL CELL CELL CELL CELL CELL
1 2 3 4 5 6 7 8 9 10 11 12
28’h 28’h 28’h 28’h 28’h 28’h 28’h 28’h 28’h 28’h 28’h 28’h
406 3E4 0 292 3E0 0 290 3D0 0 151 502 6D6
AD
F0
36
E
• Balance Status Register: Set up balance:
Cells 1, 4, 7 and 10 on 1^st cycle.
Cells 3, 6, 9 and 12 on 2^nd cycle.
Cells 2, 5, 8 and 11 on 3^rd cycle
(See Table 59)
TABLE 59. BALANCE STATUS SETUP
CELL
BPS
[3:0] 1 2 3 4 5 6 7 8 9 10 11 12
0000 Reserved for Manual Balance mode and Timed Balance mode
0001 1 0 0 1 0 0 1 0 0 1 0 0
0010 0 0 1 0 0 1 0 0 1 0 0 1
0011 0 1 0 0 1 0 0 1 0 0 1 0
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June 16, 2016