MIC2196 Micrel Semiconductor, MIC2196 Datasheet - Page 6

• Manufacturer Part Number: MIC2196
• Description: 400kHz SO-8 Boost Control IC
• Manufacturer: Micrel Semiconductor

MIC2196
Functional Diagram
Functional Description
The MIC2196 is a BiCMOS, switched-mode multi-topology
controller. It will operate most low-side drive topologies
including boost, SEPIC, flyback and forward. The controller
has a low impedance driver capable of switching large N-
channel MOSFETs. It features multiple frequency and duty
cycle settings. Current mode control is used to achieve
superior transient line and load regulation. An internal correc-
tive ramp provides slope compensation for stable operation
above a 50% duty cycle. The controller is optimized for high-
efficiency, high-performance DC-DC converter applications.
Figure 1 shows a block diagram of the MIC2196 configured
as a PWM boost converter.
MIC2196
V
IN
EN/UVLO
COMP
V
DD
3
2
5
fs/4
Osc
Corrective
Ramp
V
DD
Control
100k
Figure 1. MIC2196 Block Diagram
Amplifier
C
Error
DECOUP
gm = 0.0002
Overcurrent Reset
PWM
Comparator
On
Gain = 20
GND
GND
6
V
Bias
IN
fs/4
8
V
REF
6
Gain = 3.7
The switching cycle starts when OUTN goes high and turns
on the low-side, N-channel MOSFET, Q1. The V
MOSFET is equal to V
inductor. The inductor current flows through the current
sense resistor, R
amplified and combined with an internal ramp for stability.
This signal is compared with the error voltage signal from the
error amplifier. When the current signal equals the error
voltage signal, the low-side MOSFET is turned off. The
inductor current then flows through the diode, D1, to the
output. The MOSFET remains off until the beginning of the
next switching cycle.
Frequency
Foldback
V
V
REF
DD
0.11V
Overcurrent
Comparator
0.3V
C
SENSE
IN
IN
OUTN
7
CS
4
V
2
fb
. This forces current to ramp up in the
. The voltage across the resistor is
L1
R
SENSE
D1
C
OUT
R1
R2
V
OUT
August 2004
GS
Micrel
of the