UC3845BVN ON Semiconductor, UC3845BVN Datasheet - Page 10
UC3845BVN
Manufacturer Part Number
UC3845BVN
Description
IC CTRLR CURRENT MODE HP 8DIP
Manufacturer
ON Semiconductor
Datasheet
1.UC3844BDR2G.pdf
(19 pages)
Specifications of UC3845BVN
Pwm Type
Current Mode
Number Of Outputs
1
Frequency - Max
275kHz
Duty Cycle
50%
Voltage - Supply
8.2 V ~ 25 V
Buck
No
Boost
Yes
Flyback
Yes
Inverting
Yes
Doubler
No
Divider
No
Cuk
No
Isolated
Yes
Operating Temperature
-40°C ~ 105°C
Package / Case
8-DIP (0.300", 7.62mm)
Frequency-max
275kHz
Duty Cycle (max)
48 %
Output Voltage
4.9 V to 5.1 V
Output Current
1000 mA
Mounting Style
Through Hole
Switching Frequency
500 KHz
Operating Supply Voltage
30 V
Maximum Operating Temperature
+ 70 C
Fall Time
50 ns
Minimum Operating Temperature
0 C
Rise Time
50 ns
Synchronous Pin
No
Topology
Boost, Flyback
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Other names
UC3845BVNOS
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
UC3845BVN
Manufacturer:
MOTOROLA/摩托罗拉
Quantity:
20 000
V
R
R
t SoftStart + * In 1 *
Clamp
2
1
R
R
8(14)
2
1
V
4(7)
2(3)
1(1)
Clamp
8(14)
4(7)
2(3)
1(1)
≈
Figure 20. Adjustable Reduction of Clamp Level
MPSA63
Figure 22. Adjustable Buffered Reduction of
≈
R 2
R 1
EA
1.67
R
R
) 1
EA
R 2
R 1
R
R
+
1.67
Osc
) 1
Bias
+
1.0 mA
Clamp Level with Soft−Start
Osc
+ 0.33x10
Bias
1.0 mA
2R
3V Clamp
R
2R
V C
R
Where: 0 ≤ V
V
5(9)
-3
Clamp
1.0V
-
+
V
1.0V
5(9)
Clamp
5.0V Ref
-
R 1 ) R 2
+
C
R 1 R 2
5.0V Ref
R 1 ) R 2
R 1 R 2
Comp/Latch
Clamp
Comp/Latch
R
S
T
Q
S
R
≤ 1.0 V
T
Where: 0 ≤ V
I pk(max) [
Q
I pk(max) [
+
-
+
-
7(12)
V
7(12)
CC
Clamp
V
7(11)
6(10)
5(8)
3(5)
V Clamp
CC
R S
7(11)
6(10)
5(8)
3(5)
http://onsemi.com
≤ 1.0 V
V Clamp
R S
Q1
R
V
in
S
V
Q1
R
10
in
S
-
+
Virtually lossless current sensing can be achieved with the implementation
of a SENSEFETt power switch. For proper operation during over-current
conditions, a reduction of the I
Refer to Figures 20 and 22.
5.0V Ref
Figure 23. Current Sensing Power MOSFET
C
Control Circuitry Ground:
S
R
Comp/Latch
T
Q
1.0M
8(14)
4(7)
2(3)
1(1)
t
To Pin (9)
Soft-Start
Figure 21. Soft−Start Circuit
+
-
≈ 3600C in mF
(12)
pk(max)
EA
V
R
R
(11)
(10)
(8)
(5)
CC
+
clamp level must be implemented.
Osc
G
1.0mA
Bias
1/4 W
R
S
D SENSEFET
M
2R
V
R
in
Then : V Pin 5 [ 0.075 I pk
V Pin 5 [
If: SENSEFET = MTP10N10M
K
To Input Source
Power Ground:
S
5(9)
Return
1.0V
-
+
5.0V Ref
R
r DM(on) ) R S
R S I pk r DS(on)
S
= 200
S
R
T
Q