MIC2296 Datasheet, PDF (6/10 Pages) Micrel Semiconductor – High Power Density 1.2A Boost Regulator

Micrel
MIC2296
Functional Description
The MIC2296 is a high power density, PWM dc/dc boost
regulator. The block diagram is shown in Figure 1. The
MIC2296 is composed of an oscillator, slope
compensation ramp generator, current amplifier, gm error
amplifier, PWM generator, and a 1.2A bipolar output
transistor. The oscillator generates a 600kHz clock. The
clock’s two functions are to trigger the PWM generator that
turns on the output transistor, and to reset the slope
compensation ramp generator. The current amplifier is
used to measure the switch current by amplifying the
voltage signal from the internal sense resistor. The output
of the current amplifier is summed with the output of the
slope compensation ramp generator. This summed
current-loop signal is fed to one of the inputs of the PWM
generator.
The g_m error amplifier measures the feedback voltage
through the external feedback resistors and amplifies the
error between the detected signal and the 1.24V reference
voltage. The output of the g_m error amplifier provides the
voltage-loop signal that is fed to the other input of the
PWM generator. When the current-loop signal exceeds the
voltage-loop signal, the PWM generator turns off the
bipolar output transistor. The next clock period initiates the
next switching cycle, maintaining constant frequency
current-mode PWM control
VIN FB OVP*
EN
MIC2296
OVP*
g_m
V_REF
1.24V
SW
PWM
Generator
CA
600kHz
Oscillator
Ramp
Generator
*OVP available on MLF^TM package option only.
MIC2296 Block Diagram
Figure 1
GND
April 2005
6
M9999-042005
[phone]