The MIC2253 is a high power density 1MHz PWM DC/DC boost regulator. The 3.5A minimum switch current limit combined with a 1MHz switching frequency allows the MIC2253 to use smaller inductors and deliver high power in a tiny solution size.
The 2.5V to 10V input voltage range of MIC2253 allows direct operation from 1 and 2 cell Li-ion as well as 3 to 4 cell NiCad, NiMH, Alkaline or lithium batteries. Maximum battery life is assured with a low 0.1μA shutdown current. The MIC2253 is available in a low profile 12-pin 3mm x 3mm MLF package. To prevent a high inrush current, a minimum 1ms soft-start period is set by default and the MIC2253 has the ability to extend the soft-start period with an external capacitor.
The MIC2253 is a constant frequency, pulse-width modulated (PWM) peak current-mode step-up regulator. The device’s simplified control scheme is illustrated in the block diagram above. A reference voltage is fed into the PWM engine where the duty cycle output of the constant frequency PWM engine is computed from the error, or difference, between the REF and FB voltages. The PWM engine encompasses the necessary circuit blocks to implement a current-mode boost switching power supply. The necessary circuit blocks include, but are not limited to, an oscillator/ramp generator, slope compensation ramp generator, gm error amplifier, current amplifier, PWM comparator, and drive logic for the internal 3.5A bipolar power transistor.
Inside the PWM engine, the oscillator functions as a trigger for the PWM comparator that turns on the bipolar power transistor and resets the slope compensation ramp generator. The current amplifier is used to measure the power transistor’s current by amplifying the voltage signal from the sense resistor connected to the emitter of the bipolar power transistor. The output of the current amplifier is summed with the output of the slope compensation ramp generator where the result is connected to one of the inputs of the PWM comparator.
The gm error amplifier measures the feedback voltage through the external resistor and amplifies the error between the detected voltage signal from the feedback and the internal reference voltage. The output of the gm error amplifier provides the voltage loop signal that is fed to the other input of the PWM comparator. When the current loop signal exceeds the voltage loop signal the PWM comparator turns off the power transistor. The next oscillator/clock period initiates the next switching cycle, maintaining the constant frequency current-mode PWM control. The enable pin shuts down the output switching and disables control circuitry to reduce input current-to leakage levels. Enable pin input current is approximately zero, at zero volts.
The MIC2253 is a constant-frequency boost converter. It can convert a low DC input voltage to a high DC ou
MICROCHIP MIC2253-06YML-TR