MIC4690 Datasheet, PDF (8/12 Pages) Micrel Semiconductor – 500kHz 1A SuperSwitcher Buck Regulator

MIC4690
Applications Information
Adjustable Regulators
Adjustable regulators require a 1.23V feedback signal. Rec-
ommended voltage-divider resistor values for common out-
put voltages are included in Figure 1b.
For other voltages, the resistor values can be determined
using the following formulas:
V_OUT
=
V_REF

R1
R2
+ 1^{}
R1
=
R2


V_OUT
V_REF

− 1_
V_REF = 1.23V
Micrel
+6.8V to +30V
SHUTDOWN
ENABLE
C1
22µF
35V
Power
SOP-8
MIC4690BM
2 _VIN
SW ³
1 _SHDN
FB ⁴
GND
5Ð8
L1
18µH
D1
2A
40V
R1
3.01k
R2
1.27k
5.0V/1A
C2
220µF
10V
Figure 1a. Adjustable Regulator Circuit
Bill of Material Matrix
V_OUT R1⁽¹⁾ R2⁽¹⁾
5.0V 3.01k 976Ω
5.0V 3.01k 976Ω
3.3V 3.01k 1.78k
2.5V 3.01k 2.94k
1.8V 3.01k 6.49k
V_IN
6.8V-30V
C_IN
22µF, 35V
Vishay-Dale
595D226X0035D2T
Micro Commercial
6.8V-14V
47µF, 20V
Vishay-Dale
595D476X0020C2T
Micro Commercial
4.9V-14V
47µF, 20V
Vishay-Dale
595D476X0020C2T
Micro Commercial
4.25V-14V 47µF, 20V
Vishay-Dale
595D476X0020C2T
Micro Commercial
4.0V-14V
47µF, 20V
Vishay-Dale
595D476X0020C2T
Micro Commercial
D1
2A, 40V
Schotty
SS24
2A, 20V
Schotty
SS22
2A, 20V
Schotty
SS22
2A, 20V
Schotty
SS22
2A, 20V
Schotty
SS22
L1
18µH
Sumida
CDRH6D38-180ML
18µH
Sumida
CDRH6D38-180ML
15µH
Sumida
CDRH6D38-150ML
10µH
Sumida
CDRH6D38-100ML
10µH
Sumida
CDRH6D38-100ML
C_OUT
220µF, 10V
Vishay-Dale
594D227X0010D2T
100µF, 6.3V
Vishay-Dale
595D107X06R3C2T
120µF, 4.0V
Vishay-Dale
595D127X0004C2T
120µF, 4.0V
Vishay-Dale
595D127X0004C2T
120µF, 4.0V
Vishay-Dale
595D127X0004C2T
Note 1. All resistors 1%
Figure 1b. Recommended Components for Common Ouput Voltages
I_OUT
see SOA
1.0A
1.0A
1.0A
1.0A
MIC4690
8
June 2001