SLUUCG7 April 2024 BQ76922
The BQ76922 voltage measurements are taken in a measurement loop that consists of multiple measurement slots. All 5-cell voltages are measured on each loop, then one slot is used for one of the VC5 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 7 (if no thermistors or ADCIN are enabled), 8 (if one thermistor or ADCIN is enabled), 9 (if two thermistors or ADCIN are enabled), or 10 (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 3ms (or 1.5ms if Settings:Configuration:Power Config:FASTADC is set), so a typical measurement loop with 10 slots per loop takes 30ms (or 15ms 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 will reduce 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 the case where three or more thermistors are enabled. For example, assuming a typical measurement loop with 10 slots (30ms) per loop, and these settings configured for half speed (60ms), the device injects 10 current-only slots after each measurement loop of 10 slots.
LOOP_SLOW_1 | LOOP_SLOW_0 | Measurement Loop Cycle Time |
---|---|---|
0 | 0 | 30ms |
0 | 1 | 60ms |
1 | 0 | 120ms |
1 | 1 | 240ms |