SNVAA80 July 2024 LM5177
There are certain considerations to operate the LM5177 in the reverse direction.
The TLV431 shunt regulator is used to stop charging on the defined maximum charge voltage level. An additional PNP Transistor is used to adjust the logic level of the MODE signal. When the biasing at the Vref pin of the TLV431 reaches 1.24V, the pin starts conducting and pulls the MODE pin low and puts the LM5177 into PSM mode which stops charging.
Table 4-1 gives a summary of the LM5177 pins which must be considered especially for the reverse operation.
| PIN NAME | PIN FUNCTION | OBSERVATIONS |
|---|---|---|
| MODE | Mode Selection | The voltage at the pin determines whether the device operates in PSM mode (Mode < 0.41V) or FPWM mode (Mode > 1.19V). |
| FB | Feedback Reference | Sets the reference voltage for the voltage regulation loop. |
| EN / UVLO | Enable / Under Voltage Protection | Activates low voltage protection when the VIN voltage falls below the UVLO and enable threshold. |
| VIN | Input Voltages | The device becomes enabled when the VIN voltage exceeds the internal VDET voltage. |
| COMP | Reverse Current Regulation | Storage charging begins when the V(comp) value is less than V(comp, CL0), and constant voltage charging of the storage initiates when V(comp) equals or is greater than V(comp, CL0). |
| IMONOUT | Monitoring and Compensation | The pin monitors reverse current value or provides compensation for the average current loop. |
| SYNC | Synchronization Clock Input | For current limit in forward operation, SYNC pin needs to be connected to VCC, for reverse current limit operation, the pin needs to be connected to ground (Pulled Low) during the startup phase (EN/UVLO goes high). |
| CFG | Device Configuration Pin | Negative Current limit enabled for the reverse current operation. |