A 10 MHz ripple-based on-time controlled buck converter with dual ripple compensation

A 10 MHz ripple-based on-time controlled buck converter is presented. A novel low-cost dual ripple compensation, which consists of coupling capacitor compensation and passive equivalent series resistance compensation, is proposed to achieve a fast load transient response and robust stability simultaneously. Implemented in a 2P4M 0.35 um CMOS process, the converter achieves fix-frequency output with a ripple of below 10 mV and an overshoot of 10 mV at 400 mA step load transient response. With width optimization of the power transistors in an ultra-heavy load and PFM control in a light load, the efficiency stays at over 83% for a load range from 20 mA to 1.5 A and the peak efficiency reaches 90.16%.

A dual-path,current-sensing resistor-free boost LED driver with fast PWM dimming

A boost LED driver featuring a high PWM dimming ratio and optimized efficiency is presented. This LED driver, which has a low dropout voltage and is able to drive 3-7 LEDs in series with constant output current and fast PWM dimming, provides an alternative technique for brightness adjustment. A dual-path control scheme with automatic switching and state maintenance is proposed. Meanwhile, a cascode current mirror structure is applied with the output transistor multiplexed as an LED PWM dimming transistor. Implemented in 0.5 #m 25 V BCD process, the measurement results show that a voltage conversion range of 5 V input to 6-24 V output with constant output current is obtained. With automatically switching dual-path control and an optimized current mirror, the response time during PWM dimming is reduced to as low as 240 ns and the efficiency keeps above 89% over a wide PWM dimming ratio @ 250 mA output current.

VCCS controlled LDO with small on-chip capacitor

A stable LDO using VCCS （voltage control current source） is presented. The LDO is designed and implemented on GF 2P4M 0.35μm CMOS technology. Compared with a previous compensation scheme, VCCS can implement a real stable LDO with a small on-chip capacitor of 1 pF, whose stability is not affected by the variable ESR （equivalent series resistance） of the output capacitor. The unit gain frequency of the LDO loop can achieve 1.5 MHz, improving the transient response. The PSR of the LDO is larger than 45 dB within 0-40 kHz. The static current of the LDO at heavy load of 100 mA is 57 μA and the dropout voltage of the LDO is 150 mV. Experimental results show that a setting time of 10 ks is achieved, and the variation of output voltage is smaller than 35 mV for a 100 mA load step in transient response of the LDO.

A 1500 mA,10 MHz on-time controlled buck converter with ripple compensation and efficiency optimization

A 1500 mA,10 MHz self-adaptive on-time （SOT） controlled buck DC-DC converter is presented. Both a low-cost ripple compensation scheme （RCS） and a self-adaptive on-time generator （SAOTG） are proposed to solve the system stability and frequency variation problem. Meanwhile a self-adaptive power transistor sizing （SAPTS） technique is used to optimize the efficiency especially with a heavy load. The circuit is implemented in a 2P4M 0.35μm CMOS process. A small external inductor of 0.47 μH and a capacitor of 4.7 μF are used to lower the cost of the converter and keep the output ripple to less than 10 mV. The measurement results show that the overshoot of the load transient response is 8 mV @ 200 mA step and the dynamic voltage scaling （DVS） performance is a rise of 16/zs/V and a fall of 20 μs/V. With a SAPTS technique and PFM control, the efficiency is maintained at more than 81% for a load range of 20 to 1500 mA and the peak efficiency reaches 88.43%.