MIC38C42/3/4/5
Test
Line Regulation
Efficiency
Conditions
V
IN
= 26V to 80V, I
O
= 2A
Results
0.5%
0.6%
90%
100mV
Symbol
CT1
T1
L1
1.
2.
Micrel, Inc.
Custom Coil
1
4923
4924
4925
ETS
2
ETS 92420
ETS 92419
ETS 92421
Load Regulation V
IN
= 48V, I
O
= 0.2A to 2A
Output Ripple
V
IN
= 48V, I
O
= 2A (20MHz BW)
V
IN
= 48V, I
O
= 2A
Custom Coils, Alcester, SD tel: (605) 934-2460
Energy Transformation Systems, Inc. tel: (415) 324-4949.
Synchronous Buck Converter
Refer to figure 2. This MIC38C43 synchronous buck converter
uses an MIC5022 half-bridge driver to alternately drive the
PWM switch MOSFET (driven by GATEH, or high-side output)
and a MOSFET which functions as a synchronous rectifier
(driven by the GATEL, or low-side output).
The low-side MOSFET turns on when the high-side MOS-
FET is off, allowing current to return from ground. Current
flows through the low-side MOSFET in the source to drain
direction.
The on-state voltage drop of the low-side MOSFET is lower
than the forward voltage drop of an equivalent Schottky recti-
fier. This lower voltage drop results in higher efficiency.
A sense resistor (5mΩ) is connected to the driver’s high-
side current sense inputs to provide overcurrent protection.
Refer to the MIC5020, MIC5021, and MIC5022 data sheets
for more information.
+12V
10k
0.15µF
0.1µF
MIC5022
0.1µF
SMP60N06-14
VDD
GATEH
VB
GATEL
SH+
5mΩ
35µH
NC
6.8k
300k
FL T
EN
V
OUT
5V, 8A
4.7nF
MIC38C43
COM P V R E F
FB
ISNS
VDD
VOUT
GND
NC
470µF
25V
4.3k
IN
NC
CT
1000µF
Low ESR
47k
SH–
SL+
2200
pF
3.3k
RT/CT
0.1µF*
MKS2
GND
10k
S L–
*Locate near the MIC38C43 supply pins.
Figure 2. 100kHz, Synchronous Buck Converter
M9999-091107
8
September 2007
MICREL [ MICREL SEMICONDUCTOR ]
