MIC2182YM Micrel Inc, MIC2182YM Datasheet - Page 11

• Manufacturer Part Number: MIC2182YM
• Description: IC,SMPS CONTROLLER,CURRENT-MODE,BICMOS,SOP,16PIN,PLASTIC
• Manufacturer: Micrel Inc
• Type: Step-Down (Buck)r

Specifications of MIC2182YM

• Rohs Compliant: YES
• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 6 V
• Current - Output: 20A
• Frequency - Switching: 300kHz
• Voltage - Input: 4.5 ~ 32 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Power - Output: 400mW
• Number Of Pwm Outputs: 1
• On/off Pin: Yes
• Adjustable Output: Yes
• Topology: Boost/Buck
• Switching Freq: 330KHz
• Operating Supply Voltage (max): 32V
• Output Current: 20mA
• Output Voltage: 1.25 to 6V
• Synchronous Pin: Yes
• Rise Time: 60ns
• Fall Time: 60ns
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 16
• Package Type: SOP N
• Duty Cycle: 86%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-1068

A block diagram of the MIC2182 PWM current-mode control
loop is shown in Figure 3 and the PWM mode voltage and
current waveforms are shown in figure 5A. The inductor
current is sensed by measuring the voltage across the
resistor, R
signal to provide slope compensation, which is required to
prevent unstable operation at duty cycles greater than 50%.
A transconductance amplifier is used for the error amplifier,
which compares an attenuated sample of the output voltage
with a reference voltage. The output of the error amplifier is
the COMP (compensation) pin, which is compared to the
current-sense waveform in the PWM block. When the current
signal becomes greater than the error signal, the comparator
turns off the high-side drive. The COMP pin (pin 3) provides
access to the output of the error amplifier and allows the use
of external components to stabilize the voltage loop.
April 22, 2004
MIC2182
CS
. A ramp is added to the amplified current-sense
MIC2182 [adj.] Skip Mode
CONTROL LOGIC AND
SKIP-MODE LOGIC
ONE SHOT
R
Q
LOW-SIDE DRIVER
S
ONE SHOT
LOW
FORCES
PWM MODE
Skip-Mode
Current
Limit
Low
Comp
Hysteresis
Comp
1%
–2%V
Figure 4. Skip-Mode Operation
0.07V
Reference
BG
V
V
Current
Sense
Amp
A
DD
IN
V
= 2
11
Skip-Mode Control Loop
This control method is used to improve efficiency at light
output loads. At light output currents, the power drawn by the
MIC2182 is equal to the input voltage times the IC supply
current (I
the IC can be a significant portion of the total output power,
which lowers the efficiency of the power supply. The MIC2182
draws less supply current in skip mode by disabling portions
of the control and drive circuitry when the IC is not switching.
The disadvantage of this method is greater output voltage
ripple and variable switching frequency.
A block diagram of the MIC2182 skip mode is shown in Figure
4. Skip mode voltage and current waveforms are shown in
figure 5B.
Q
VDD
11
VIN
10
VBST
14
HSD
16
VSW
15
LSD
13
PGND
12
CSH
8
VOUT
9
FB
7
). At light output currents, the power dissipated by
V
IN
Q2
Q1
V
OUT
C
D2
C
IN
1.245V
BST
L1
4.7 F
1
R2
R1
R
CS
R1
R2
V
C
OUT
OUT
M9999-042204
Micrel