MIC2295 Micrel Semiconductor, MIC2295 Datasheet - Page 8

• Manufacturer Part Number: MIC2295
• Description: High Power Density 1.2A Boost Regulator
• Manufacturer: Micrel Semiconductor

Functional Description
The MIC2295 is a high power density, PWM dc/dc
boost regulator. The block diagram is shown in
Figure 1. The MIC2295 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 1.2MHz clock. The clock’s two functions
are to trigger the PWM generator that turns on the
output
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
July 2004
Micrel
transistor,
*
and
OVP available on MLF
VIN
to
1.24V
FB
OVP*
reset
OVP*
g
TM
m
package option only.
the
Oscillator
1.2MHz
slope
MIC2295 Block Diargam
8
Generator
Generator
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
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
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
Ramp
PWM
EN
Σ
m
MIC2295
error amplifier measures the feedback
CA
SW
GND
[phone]
M9999-052402
MIC2295
m