SLUSDF9 June 2020 BQ25790
At POR, the charger detect the PROG pin pull down resistance, then sets the charger default POR switching frequency and the battery cell count. Please follow the resistance list in the table below to set the desired POR switching frequency and battery cell count. The surface mount resistor with ±1% or ±2% tolerance is recommended.
|SWITCHING FREQUENCY||CELL COUNT||TYPICAL RESISTANCE AT PROG PIN|
|1.5 MHz||1s||3.0 kΩ|
|750 kHz||1s||4.7 kΩ|
|1.5 MHz||2s||6.04 kΩ|
|750 kHz||2s||8.2 kΩ|
|1.5 MHz||3s||10.5 kΩ|
|750 kHz||3s||13.7 kΩ|
|1.5 MHz||4s||17.4 kΩ|
|750 kHz||4s||27.0 kΩ|
Some of the charging parameters default values are determined by the battery cell count identified by PROG pin configuration, which are summarized in the table below.
|ICHG (REG0x03/04)||2 A||2 A||1 A||1 A|
|VSYSMIN (REG0x00[5:0])||3.5 V||7 V||9 V||12 V|
|VREG (REG0x01/02)||4.2 V||8.4 V||12.6 V||16.8 V|
|VREG Range||3 V - 4.99 V||5 V - 9.99 V||10 V - 13.99 V||14 V - 18.8 V|
After POR, the host can program the ICHG and VSYSMIN registers to any values within the ranges defined in the register tables. However, when programming the battery charging voltage (VREG), the host must ensure the VREG value falling into the right range associated with the CELL register (REG0x0A[7:6]) setting defined in the table above. When the CELL register is changed, the ICHG, VSYSMIN and VREG registers are reset to the POR default values associated with the CELL setting.
For example, if the PROG pin resistance is a 2s battery configuration, the default POR CELL, ICHG, VSYSMIN and VREG settings will be 2s, 2 A, 7 V and 8.4 V respectively. After POR, the host can change ICHG and VSYSMIN to any other values, and change VREG to any other values between 5V and 9.99V. With the CELL bits stay at 2s battery configuration, when REG_RST bit or watchdog timer expired, the registers are reset to default values with ICGH, VSYSMIN and VREG automatically return to 2A, 7V, 8.4V respectively.
When the CELL register is 2s battery configuration, any write out of the range of VREG (5 V - 9.99 V) is ignored by the charger. If VREG needs to be programmed out of the 5 V - 9.9 V range, like 11 V, the CELL bits have to be changed to 3s setting. The ICHG, VSYSMIN and VREG registers are reset to the 3s POR default values first, which are 1 A, 9 V and 12.6 V. After that, the host can program VREG in the range of 10 V - 13.99 V. In addition, when the CELL setting is changed to 3s, ICHG, VSYSMIN and VREG return to 1 A, 9 V and 12.6 V, when the registers are reset to the default values by REG_RST bit or the watchdog timer expiration.