UC3843BVD ON Semiconductor, UC3843BVD Datasheet - Page 12

• Manufacturer Part Number: UC3843BVD
• Description: IC CTRLR CURRENT MODE HP 14SOIC
• Manufacturer: ON Semiconductor

Specifications of UC3843BVD

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 275kHz
• Duty Cycle: 96%
• Voltage - Supply: 8.2 V ~ 25 V
• Buck: No
• Boost: Yes
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Frequency-max: 275kHz
• Duty Cycle (max): 96 %
• Output Voltage: 4.9 V to 5.1 V
• Output Current: 1000 mA
• Mounting Style: SMD/SMT
• Switching Frequency: 500 KHz
• Operating Supply Voltage: 30 V
• Maximum Operating Temperature: + 105 C
• Fall Time: 50 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 50 ns
• Synchronous Pin: No
• Topology: Boost, Flyback, Forward
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: UC3843BVDOS

C
-
+
Virtually lossless current sensing can be achieved with the implementation of a
SENSEFET power switch. For proper operation during over-current conditions, a
reduction of the I
1.0M
Figure 26. Current Sensing Power MOSFET
5.0V Ref
8(14)
4(7)
2(3)
1(1)
Comp/Latch
pk(max)
S
R
t
Soft-Start
Q
Figure 24. Soft−Start Circuit
Control Circuitry Ground:
clamp level must be implemented. Refer to Figures 23 and 25.
≈ 3600C in mF
To Pin (9)
EA
+
R
R
-
+
(12)
Osc
1.0mA
Bias
V
(11)
(10)
(8)
(5)
CC
2R
G
R
1/4 W
S
R
-
+
D
M
5(9)
1.0V
SENSEFET
V
in
Then : V Pin 5 [ 0.075 I pk
V Pin 5 [
If: SENSEFET = MTP10N10M
R
5.0V Ref
K
To Input Source
S
S
Power Ground:
= 200
Return
S
R
r DM(on) ) R S
R S I pk r DS(on)
Q
http://onsemi.com
C
12
R
R
2
1
8(14)
t SoftStart + * In 1 *
4(7)
2(3)
1(1)
MPSA63
V Clamp [
Figure 25. Adjustable Buffered Reduction of
Figure 27. Current Waveform Spike Suppression
EA
R
R
-
+
+
R 2
R 1
The addition of the RC filter will eliminate instability caused by the leading
edge spike on the current waveform.
Clamp Level with Soft−Start
Osc
1.67
Bias
1.0 mA
) 1
5.0V Ref
Comp/Latch
3 V Clamp
2R
V C
R
S
R
Where: 0 ≤ V
V
C
Clamp
Q
1.0V
5(9)
R 1 ) R 2
-
+
R 1 R 2
5.0V Ref
Clamp
Comp/Latch
7(12)
≤ 1.0 V
+
-
S
R
V
CC
I pk(max) [
Q
7(11)
6(10)
5(8)
3(5)
+
-
C
R
V Clamp
7(12)
R S
V
CC
V
Q1
R
7(11)
6(10)
5(8)
3(5)
in
S
Q1
V
R
in
S