MITSUBISHI <Dig./Ana. INTERFACE>
M62220L/FP
3.3V FIXED OUTPUT VOLTAGE DC-DC CONVERTER
Application Circuit (3.3V Output DC-DC Converter)
VIN (5V)
RCLM
0.1Ω
+ 100µF
VOUT(3.3V,1A)
+
100µF
5 IN
4
3
Vcc
CLM
M62220 Collector 1
GND
2
1KΩ
1KΩ
47µ H
Fig.1 Example of the M62220L/FP application circuit
Current Limit Detection:
When the voltage drop between pin 3 and pin 4 becomes more than 150mV,
the Current Limit Detection circuit begins operating. The peak switch
current "Ipk" is limited to 150mV / RCLM. In the example of application
(fig.1), the current is limited to 1.5A.
THE EXPRESSION OF CIRCUIT CONSTANTS
CONSTANTS
TON
TOFF
(TON+TOFF)MAX
TOFF(MIN)
TON(MAX)
L(MIN)
Ipk
RCLM
EXPRESSIONS
VO+VF
VIN - VCE(sat) - VO
1
fosc
fosc:110KHz(Vcc=5V)
( TON + TOFF )
/ (1+
TON )
TOFF
1
fosc - TOFF
( VIN - VCE(sat) - VO ) · TON(MAX)
∆Io
Io
+
1
2
∆Io
0.15 ∆VCLM:150mV(Vcc=5V)
Ipk
•VF : Forward voltage drop of an external diode.
•Vsat : Output saturation voltage of an external switching transistor.
•∆Io : It should be set between 1/3 and 1/5 of maximum output current.
•An external transistor, diode and inductor should have a peak current capability of
greater than "Ipk".
(3/3)
April. 1997