8.1 Overview

The TPS65217x device has three step-down converters, two low-dropout (LDO) regulators, two load switches, a linear battery charger, a white LED driver, and a power path. The system can be supplied by any combination of a USB port, 5-V AC adaptor, or Li-ion battery. The device is characterized across a temperature range from –40°C to +105°C, making it suitable for industrial applications where a 5-V power supply rail is available. The device offers configurable power-up and power-down sequencing and several low-speed, system-level functions such as a power-good output, push-button monitor, hardware-reset function, and temperature sensor to protect the battery.

The I²C interface has comprehensive features for using the TPS65217x device. All rails, load switches, and LDO regulators can be enabled or disabled. Power-up and power-down sequences, overtemperature thresholds, and overcurrent threshold can be programmed through the I²C interface. The I²C interface also monitors battery charging and controls LED dimming parameters.

The three DC/DC step-down converters can each supply up to 1.2 A of current. The output voltages for each converter can be adjusted through the I²C interface in real time to support processor clock frequency changes. All three converters feature dynamic voltage positioning to decrease voltage undershoots and overshoots. Typically, the converters work at a fixed-frequency of 2.25 MHz, pulse-width modulation (PWM) at moderate-to-heavy load currents. At light load currents the converters automatically go to power save mode and operate in pulse-frequency modulation (PFM) for maximum efficiency across the widest possible range of load currents. For low-noise applications, each converter can be forced into fixed-frequency PWM using the I²C interface. The step-down converters allow the use of small inductors and capacitors to achieve a small solution size.

The device has two traditional LDO regulators: LDO1 and LDO2. The LDO1 and LDO2 regulators can support up to 100 mA each during normal operation, but in the SLEEP state they are limited to 1 mA to decrease quiescent current while supporting system-standby mode. The TPS65217A variant of the device also has two load switches: LS1 and LS2. For all other TPS65217x variants, these two outputs are configured as LDO regulators: LDO3 and LDO4. The LDO3 and LDO4 regulators can support up to 200 mA (TPS65217B), or 400 mA (TPS65217C and TPS65217D). All four LDO regulators have a wide input voltage range that allows them to be supplied either from one of the DC/DC converters or directly from the system voltage node.

The device has two power-good logic signals. The primary power-good signal, PGOOD, monitors the DCDC1, DCDC2, and DCDC3 converters, and LS1 (or LDO3) and LS2 (or LDO4) configurable power outputs. This signal is high in the ACTIVE state, but low in the SLEEP, RESET, and OFF states. The secondary power-good signal, LDO_PGOOD, monitors LDO1 and LDO2; the signal is high in the ACTIVE and SLEEP states, but low in the RESET and OFF states. The PGOOD and LDO_PGOOD signals are both pulled low when all the monitored rails are pulled low, or when one or more of the monitored rails are enabled and have encountered a fault, typically an output short or overcurrent condition.

The highly-efficient boost converter has two current sinks that can drive two strings of up to 10 LEDs at 25 mA each, or one string of 20 LEDs at 50 mA. An internal PWM signal and I²C control support brightness and dimming. Both current sources are controlled together and cannot operate independently.

The triple system power path lets simultaneous and independent powering of the system and battery charging through the linear battery charger for single-cell Li-ion and Li-Polymer batteries. The AC input is prioritized over USB input as the power source for charging the battery and powering the system. Both these sources are prioritized over the battery for powering the system to decrease the number of charge and discharge cycles on the battery.