1 Device Overview

TPS613222A See References no. 1 is a very compact boost converter with only 3 active pins. Only two external components (one inductor and one output capacitor) are needed when designing a 5-V fixed output power rail. The quiescent is 6.5uA typically and the total power loss is very small even though the boost converter is always in active state. This part reduces the system cost significantly and makes the system design quite simple. But it has no short circuit protection.

TPS613222A is a hysteretic current control boost converter. There is a current comparator inside turns on and off the power MOSFETs. During the off-phase, the high-side MOSFET is on and the low side MOSFET is off. As the output voltage is higher than the input voltage, the inductor current ramps down. When the inductor current triggers the target value set by the output of the error amplifier, the high-side MOSFET is turned off and the low-side MOSFET is turned on (dead time control is integrated). Then the inductor current starts ramping up. When the inductor current ramps up to the target value set by the hysteretic current comparator, the low-side MOSFET is turned off and high-side MOSFET is turned on again. The TPS613222A operates in this behavior back and forth. If the output load goes beyond the TPS613222A’s capability, the peak switch current will be limited to 1.8A typically and the output voltage starts to drop. When the output voltage drops to the input voltage level, the inductor current is no longer controllable because even in off-phase, the inductor current ramps up not down and the boost converter may be damaged.