General Description

The MIC3808 and MIC3809 are a family of complementary output push-pull PWM control ICs that feature high speed and low power consumption. The MIC3808/9 are ideal for telecom level (36V to 75V) isolated step down dc/dc conversion applications where high output current, small size, and high efficiency are required.

The dual-ended push-pull architecture of the MIC3808/9 allows more efficient utilization of the transformer than single ended topologies, allowing smaller size dc/dc solutions.

Additionally, the out-of-phase push-pull topology allows a higher effective duty cycle, reducing input and output ripple as well as stress on the external components. The dead-time between the two outputs is adjustable between 60ns to 200ns, limiting the duty cycle of each output stage to less than 50%.

The MIC3808/9 are built on a low-power, high-speed BiCMOS process. The 130µA start-up current and 1mA run-current reduce the size of the start-up circuitry and allow high efficiency even at light loads. The high-speed internal 4MHz error amplifier allows MIC3808/9 operation up to 1MHz.

The MIC3808 has a turn-on threshold of 12.5V whereas the MIC3809 has a lower turn-on threshold of 4.3V. Both devices are available in SOP-8 and MSOP-8 package options with an operating range of –40°C to +85°C.

Features

• Dual output drive stages in push-pull configuration

• Leading edge current-sense blanking

• 130µA typical start-up current

• 1mA typical run current

• Operation to 1MHz

• Internal soft start

• On-chip error amplifier with 4MHz gain bandwidth product

• On-chip VDD clamping

• Output drive stages capable of 500mA peak source current, 1A peak sink current

Applications

• High efficiency “brick” power supply modules

   • Half bridge converters

   • Full bridge converters

   • Push-pull converters

   • Voltage-fed push-pull converters

• Telecom equipment and power supplies

• Networking power supplies

• Industrial power supplies

• 42V automotive power supplies

• Base stations