UC2845BD1G ON Semiconductor, UC2845BD1G Datasheet - Page 11
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UC2845BD1G
Manufacturer Part Number
UC2845BD1G
Description
IC CTRLR CURRENT MODE HP 8-SOIC
Manufacturer
ON Semiconductor
Datasheet
1.UC3844BDR2G.pdf
(19 pages)
Specifications of UC2845BD1G
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
-25°C ~ 85°C
Package / Case
8-SOIC (3.9mm Width)
Frequency-max
275kHz
Duty Cycle (max)
48 % (Typ)
Output Voltage
4.95 V to 5.05 V
Output Current
1000 mA (Max)
Mounting Style
SMD/SMT
Switching Frequency
500 KHz
Operating Supply Voltage
30 V
Maximum Operating Temperature
85 C
Fall Time
50 ns
Minimum Operating Temperature
- 25 C
Rise Time
50 ns
Synchronous Pin
No
Topology
Boost or Flyback
Rohs Compliant
YES
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Figure 25. MOSFET Parasitic Oscillations
Series gate resistor R
parasitic oscillations caused by the MOSFET input
capacitance and any series wiring inductance in the
gate-source circuit.
+
-
5.0V Ref
Comp/Latch
S
R
T
Q
-
+
g
will damp any high frequency
5.0V Ref
+
-
7(12)
Comp/Latch
Figure 24. Current Waveform Spike Suppression
V
CC
R
S
7(11)
6(10)
5(8)
3(5)
T
Q
R
g
+
-
7(12)
Q1
R
V
V
in
S
CC
7(11)
6(10)
5(8)
3(5)
http://onsemi.com
C
R
11
Q1
R
V
S
in
The addition of the RC filter will eliminate
instability caused by the leading edge spike
on the current waveform.
+
0
-
The totem pole output can furnish negative base current
for enhanced transistor turn-off, with the addition of
capacitor C
Figure 26. Bipolar Transistor Drive
I
B
1
.
Base Charge
Removal
6(10)
5(8)
3(5)
C1
Q1
V
R
in
S