MIC2183YQS Micrel Inc, MIC2183YQS Datasheet - Page 8

• Manufacturer Part Number: MIC2183YQS
• Description: QSOP-16 Low Vin Synchronous Buck PWM Control IC
• Manufacturer: Micrel Inc

Specifications of MIC2183YQS

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 440kHz
• Duty Cycle: 100%
• Voltage - Supply: 2.9 V ~ 14 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 16-QSOP
• Frequency-max: 440kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-2160; MIC2183YQS

MIC2183
Functional Diagram
Functional Characteristics
Controller Overview and Functional Description
The MIC2183 is a BiCMOS, switched mode, synchronous,
step down (buck) converter controller. It uses both N and P-
Channel MOSFETs, which allows the controller to operate at
100% duty cycle and eliminates the need for a high side drive
bootstrap circuit. 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 is a block diagram of the MIC2183 configured as a
synchronous buck converter. At the beginning of the switch-
ing cycle, the OUTP pin pulls low and turns on the high-side
M9999-042205
EN/UVLO
FREQ/2
FreqOut
COMP
SYNC
VDD
SS
7
10
11
15
2
3
4
÷2
OSC
fs/4
COMPARATOR
C
DECOUP
VDD
PWM
COMPENSATION
RESET
VINA
CONTROL
SLOPE
BIAS
1
ON
Figure 1. MIC2183 Block Diagram
1.245V
VREF
fs/4
100k
∑
CURRENT
FREQUENCY
FOLDBACK
OVERCURRENT
SENSE
COMPARATOR
AMP
gm = 0.0002
gain = 20
8
ERROR
P-Channel MOSFET, Q1. Current flows from the input to the
output through the current sense resistor, MOSFET and
inductor. The current amplitude increases, controlled by the
inductor. The voltage developed across the current sense
resistor, R
bined with an internal ramp for stability. This signal is com-
pared to the output of the error amplifier. When the current
signal equals the error voltage signal, the P-channel MOSFET
is turned off. The inductor current flows through the diode, D1,
until the synchronous, N-Channel MOSFET turns on. The
voltage drop across the MOSFET is less than the forward
voltage drop of the diode, which improves the converter
efficiency. At the end of the switching period, the synchro-
nous MOSFET is turned off and the switching cycle repeats.
AMP
GAIN
3.7
0.3V
V
0.1V
REF
PGND
16
14
13
12
9
8
6
5
CSH
CSL
VINP
OUTP
OUTN
PGND
FB
SGND
SENSE
, is amplified inside the MIC2183 and com-
Q1
Q2
R
SENSE
C
IN
D1
V
L1
IN
C
OUT
Micrel, Inc.
April 2005
V
OUT