The control circuit of the TPS5516x-Q1 buck-boost converter is based on an average current-mode topology. The control circuit also uses input and output voltage feedforward. Changes of input and output voltage are monitored and the duty cycle in the modulator is immediately adapted to achieve a fast response to those changes. The voltage error amplifier gets its feedback input from the VOS_FB pin. The feedback voltage is compared with the internal reference voltage to generate a stable and accurate output voltage.

The buck-boost converter uses four internal N-channel MOSFETs to maintain synchronous power conversion at all possible operating conditions. This feature enables the device to keep high efficiency over a wide input voltage and output power range. To avoid ground shift problems caused by the high currents in the switches, separate ground pins (GND and PGND) are used. The reference for all control functions are the GND pins. The power switches are connected to the PGND pins. Both grounds must be connected on the PCB at only one point which is ideally close to the GND pin. Because of the 4-switch topology, the load is always disconnected from the input during shutdown of the converter.

To drive the high-side switches of the buck and the boost power stages, the buck-boost converter requires external boot-strapping ceramic capacitors with low ESR. These bootstrap capacitors are charged by the VREG supply. The VREG supply requires a low-ESR ceramic capacitor for loop stabilization, and must not be loaded by the external application. The VREG supply is also used to drive the low-side switches of the buck and boost power stages. At device start-up, the VREG pin is supplied by the input voltage. When the buck-boost output voltage is greater than its power-good threshold (the PG pin is high), the VREG pin is supplied by the output voltage to reduce power dissipation.

The device can be enabled with the IGN pin, and, when enabled, the device has a power-latch function which can be selected with the IGN_PWRL pin. This function allows an external MCU to keep TPS5516x-Q1 device on even after the IGN pin goes low.

For the TPS55160-Q1 and TPS55165-Q1 devices, the operation mode of the buck-boost converter can be selected through the PS pin. When the PS pin is low, the buck-boost operates in normal mode with a constant fixed switching frequency. When the PS pin is high, the buck-boost operates in low-power mode with pulse-frequency modulation.

The TPS55160-Q1 and TPS55165-Q1 devices also have a frequency spread-spectrum option that can be enabled or disabled through the SS_EN pin.

The output voltage of the TPS55165-Q1 device is selected as a fixed 5 V or fixed 12 V through the VOS_FB pin. The TPS55160-Q1 and TPS55162-Q1 devices have an adjustable output voltage from 5.7 V to 9 V through an external feedback network.