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| MIC2186 Datasheet, PDF (8/16 Pages) Micrel Semiconductor – Low Voltage PWM Control IC | |||
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MIC2186
VIN
EN/UVLO
7
VDD
SKIP
2
HiDC
13
Freq/2
15
Sync
11
Soft Start
3
COMP
4
VREF
8
VDD
10
CDECOUP
VINA 1
Bias
On
Control
CIN
VREF
VDD
PGND
L1
VINP
16
D1
OutN
Q1
14
COUT
VOUT
Osc
VREF
VDD
Current
Reset
50mV
Skip Current
Limit Comparator
PGND
VREF
1.245V
CSH
9
RSENSE
PGND
12
R1
Vfb
6
Hysteresis
R2
Comparator
±1%
SGND
SGND 5
Figure 2. MIC2186 SKIP Mode Block Diagram
Micrel
The description of the MIC2186 controller is broken
down into 6 basic functions.
⢠Control Loop
⢠PWM Operation
⢠SKIP Mode Operation
⢠Current Limit
⢠MOSFET gate drive
⢠Reference, enable & UVLO
⢠Oscillator & Sync
⢠Soft start
Control Loop
PWM and SKIP modes of operation
The MIC2186 can operate in either PWM (pulse width modu-
lated) or SKIP mode. The efficiency of the boost converter
can be improved at lower output loads by manually selecting
the skip mode of operation. The potential disadvantage of
skip mode is the variable switching frequency that accompa-
nies this mode of operation. The occurrence of switching
pulses depends on component values as well as line and load
conditions. PWM mode is the best choice of operation at
higher output loads. PWM mode has the advantages of lower
output ripple voltage and higher efficiencies at higher output
loads. Pulling the SKIP pin (pin 3) low will force the controller
to operate in PWM mode for all load conditions. Pulling the
SKIP pin high will force the controller to operate in SKIP
mode.
MIC2186
8
July 2002
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