SLUUCW9 December 2023 BQ76972
The BQ76972 voltage measurements are taken in a measurement loop that consists of multiple measurement slots. All 16 cell voltages are measured on each loop, then one slot is used for one of the VC16 or PACK or LD pin voltages, one slot is used for internal temperature or Vref or VSS measurement, then up to three slots are used to measure thermistors or multifunction pin voltages (ADCIN functionality). Over the course of three loops, a full set of measurements is completed. One measurement loop consists of either 18 (if no thermistors or ADCIN are enabled), 19 (if one thermistor or ADCIN is enabled), 20 (if two thermistors or ADCIN are enabled), or 21 (if three or more thermistors or ADCIN are enabled) measurement slots.
The speed of a measurement loop can be controlled by settings. Each voltage measurement (slot) takes 3 ms (or 1.5 ms if Settings:Configuration:Power Config:FASTADC is set), so a typical measurement loop with 21 slots per loop takes 63 ms (or 31.5 ms if Settings:Configuration:Power Config:FASTADC is set). If measurement data is not required as quickly, the timing for the measurement loop can be programmed to slower speeds, which injects idle slots in each loop after the measurement slots. Using slower loop cycle time reduces the power dissipation of the device when in NORMAL mode. This is set using the Settings:Configuration:Power Config:LOOP_SLOW_0 and LOOP_SLOW_1 configuration bits, as shown below. For example, assuming a typical measurement loop with 21 slots (63 ms) per loop, and these settings configured for half speed (126 ms), the device injects 21 current-only slots after each measurement loop of 21 slots.
LOOP_SLOW_1 | LOOP_SLOW_0 | Measurement Loop Cycle Time |
---|---|---|
0 | 0 | 63 ms |
0 | 1 | 126 ms |
1 | 0 | 252 ms |
1 | 1 | 504 ms |