M5291P/FP
Constant Definition
Constant
T
ON
T
OFF
(T
ON
+ T
OFF
)
MAX
Step-down Circuit
V
OUT
+
V
F
V
IN (MIN)
−
V
sat
−V
OUT
1
f
MIN
T
ON
+
T
OFF
T
ON
1
+
T
OFF
1
−
T
OFF
f
MIN
6
×
10
−5
•
T
ON
2
•
I
OUT (MAX)
(
V
IN (MIN)
−
V
sat
−
V
OUT
)
•
T
ON (MAX)
I
PK
0.33
I
PK
1.17
×
(1
+
R
1
)
R
2
(
Step-up Circuit
V
OUT
+
V
F
−
V
IN (MIN)
V
IN (MIN)
−
V
sat
1
f
MIN
T
ON
+
T
OFF
T
ON
1
+
T
OFF
1
−
T
OFF
f
MIN
6
×
10
−5
•
T
ON
2
•
I
OUT (MAX)
•
( 1
+
V
IN (MIN)
−
V
sat
I
PK
T
ON
)
T
OFF
(
Inverse Polarity Circuit
V
OUT
+
V
F
V
IN
−
V
sat
1
f
MIN
T
ON
+
T
OFF
T
ON
1
+
T
OFF
1
−
T
OFF
f
MIN
T
OFF
T
ON
C
T
I
PK
L
(MIN)
R
SC
V
O
6
×
10
−5
•
T
ON
2
•
I
OUT (MAX)
•
(
1
+
V
IN (MIN)
−
V
sat
I
PK
T
ON
T
OFF
)
)
•
T
ON (MAX)
)
•
T
ON (MAX)
0.33
I
PK
1.17
×
(1
+
R
1
)
R
2
0.33
I
PK
1.17
×
(1
+
R
1
)
R
2
Note:
V
F
: Forward Voltage of Diode
V
sat
: Output saturation voltage of M5291 (0.6 Vmax at single output, 2.0 Vmax at Darlington output)
Setting switching frequency first and calculate each constant value.
Notes:
1. Peak current sense
In overcurrent function, oscillator is stop, when voltage descend of external detecting resistance is more than 330
mV.
2. ON/OFF Control
If you need stop the action, connected resistance (5 to 10 kΩ) between supply voltage terminal and timing capacitor
terminal.
T
ON
3.
is not established more than 0.857, because charge and discharge current ratio fixed 1 : 6.
T
ON
+ T
OFF
REJ03D0841-0300 Rev.3.00 Jun 15, 2007
Page 7 of 9
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