MIC2182YM Micrel Inc, MIC2182YM Datasheet - Page 12

• 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

MIC2182
A hysteretic comparator is used in place of the PWM error
amplifier and a current-limit comparator senses the inductor
current. A one-shot starts the switching cycle by momentarily
turning on the low side MOSFET to insure the high-side drive
boost capacitor, Cbst, is fully charged. The high-side MOS-
FET is turned on and current ramps up in the inductor, L1.
The high-side drive is turned off when either the peak voltage
on the input of the current-sense comparator exceeds the
threshold, typically 35mV, or the output voltage rises above
the hysteretic threshold of the output voltage comparator.
Once the high-side MOSFET is turned off, the load current
discharges the output capacitor, causing V
cycle repeats when V
1%.
The maximum peak inductor current depends on the skip-
mode current-limit threshold and the value of the current-
sense resistor, R
M9999-042204
I
inductor(peak)
CS
.
R
35mV
OUT
sense
falls below the lower threshold, –
V
one-shot
Reset
Pulse
V
V
V
V
V
V
V
I
HSD
HSD
OUT
OUT
LSD
LSD
SW
I
SW
I
L1
L1
V
V
IN
I
NOMINAL
LIM(skip)
+ V
I
LOAD
V
V
V
V
V
V
OUT
+1%
V
V
–1%
0A
0V
0V
0V
0V
0A
0V
0V
0A
0V
DD
DD
0V
DD
DD
DD
0V
DD
IN
IN
OUT
Figure 5a. PWM-Mode Timing
Figure 5b. Skip-Mode Timing
to fall. The
12
Figure 6 shows the improvement in efficiency that skip mode
makes when at lower output currents.
100
80
60
40
20
0.01
Figure 6. Efficiency
0
Skip
OUTPUT CURRENT (A)
0.1
1
10
PWM
100
April 22, 2004
Micrel