MIC4680 Datasheet, PDF (10/16 Pages) Micrel Semiconductor – 1A 200kHz SuperSwitcher™ Buck Regulator Final Information

MIC4680
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
V_IN
MIC4680BM
2 _IN
SW ³
L1
C_IN
R1
SHUTDOWN
ENABLE
1 _SHDN
FB ⁴
GND
D1
R2
5–8
V_OUT
C_OUT
Figure 1a. Adjustable Regulator Circuit
V_OUT R1* R2*
C_IN
1.8V 3.01k 6.49k
2.5V
3.3V
5.0V
3.01k 2.94k
3.01k
1.78k
15µF 35V
AVX TPSE156035R0200
3.01k 976Ω
6.0V 3.01k 787Ω
* All resistors 1%
** shielded magnetics for low RFI applications
*** Vishay-Diode, Inc. [phone]
D1
L1
C_OUT
68µH 1.5A
2A 60V Schottky
B260A Vishay-Diode, Inc.***
or
Coiltronics UP2B-680
or
Sumida CDRH125-680MC**
220µF 10V
AVX TPSE227010R0060
SS26 General Semiconductor
or
Sumida CDRH124-680MC**
Figure 1b. Recommended Components for Common Ouput Voltages
MIC4680
10
June 2000