M62290L/FP
Application Circuit (5 V Output DC/DC Converter)
V
IN
(12 V)
+
100
µF
R
CLM
0.09
Ω
4
V
CC
3
CLM
1 kΩ
V
OUT
(5.0 V, 1 A)
5 IN
100
µF
+
GND
2
M62290
Collector 1
1 kΩ
150
µH
Figure 1 Example of Application Circuit of the M62290L/FP
•
Current limit detection:
When the voltage drop between pin 3 and pin 4 becomes more than 140 mV, the current limit detection circuit
begins operating. The peak switch current "Ipk" is limited to 140 mV/R
CLM
. In the example of application
(Figure 1), the current is limited to 1.5 A.
The Expression of Circuit Constants
Constants
T
ON
T
OFF
(T
ON
+
T
OFF
)
MAX
T
OFF (MIN)
T
ON (MAX)
L
(MIN)
lpk
R
CLM
1
f
OSC
Expressions
V
O
+
V
F
V
IN
−
V
CE (sat)
−
V
O
f
OSC
: 120 kHz (V
CC
= 12 V)
T
ON
T
OFF
(T
ON
+
T
OFF
) / ( 1
+
1
f
OSC
−
T
OFF
)
(V
IN
−
V
CE (sat)
−
V
O
)
×
T
ON (MAX)
∆l
O
l
O
+
1
∆l
O
2
0.14
∆V
CLM
: 140 mV (V
CC
= 12 V)
Ipk
Note:
V
F
: Forward voltage drop of an external diode.
Vsat: Output saturation voltage of an external switching transistor.
∆I
O
: Set between 1/3 and 1/5 of the maximum output current.
An external transistor, diode and inductor must be have a peak current capability of approximately greater than
"Ipk".
REJ03D0850-0300 Rev.3.00 Jun 15, 2007
Page 7 of 10
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