UC3845AN STMicroelectronics, UC3845AN Datasheet - Page 5

• Manufacturer Part Number: UC3845AN
• Description: IC CURR-MODE PWM CTRLR 8-MINIDIP
• Manufacturer: STMicroelectronics

Specifications of UC3845AN

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 500kHz
• Duty Cycle: 50%
• 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: 0°C ~ 70°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Frequency-max: 500kHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 497-3083-5

High peak currents associated with capacitive loads
necessitate careful grounding techniques. Timing
and bypass capacitors should be connected close
Figure 2: Oscillator Frequency vs Timing Resis-
Figure 1: Open Loop Test Circuit.
100K
(Hz)
10K
1M
1K
f
o
ERROR AMP.
300
ADJUST
4.7K
4.7K
tance
1K
1K
ADJUST
2N2222
3K
D95IN343
I
100K
SENSE
10K
5K
30K
COMP
I
R
SENSE
R
T
T
V
/C
FB
D96IN362
T
R
T
1
2
3
4
( )
V
UC3842A
REF
8
C
T
to pin 5 in a single point ground. The transistor and
5 K potentiometer are used to sample the oscillator
waveform and apply an adjustable ramp to pin 3.
Figure 3: Maximum Duty Cycle vs Timing Resis-
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A
7
6
5
(Hz)
80
60
40
20
f
0
o
300
V
OUTPUT
GROUND
i
0.1 F
tor
1K
0.1 F
3K
A
1K
10K
1W
30K
V
V
OUTPUT
GROUND
REF
i
D96IN363
R
T
( )
5/15