UC2845BN STMicroelectronics, UC2845BN Datasheet - Page 5

• Manufacturer Part Number: UC2845BN
• Description: IC CTRLR PWM CURR-MODE 8-MINIDIP
• Manufacturer: STMicroelectronics

Specifications of UC2845BN

• 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: -25°C ~ 85°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Frequency-max: 500kHz
• Duty Cycle (max): 50 %
• Output Voltage: 4.95 V to 5.05 V
• Output Current: 1000 mA (Max)
• Mounting Style: Through Hole
• Switching Frequency: 500 KHz
• Operating Supply Voltage: 30 V
• Maximum Operating Temperature: 150 C
• Fall Time: 50 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 50 ns
• Synchronous Pin: No
• Topology: Boost or Flyback
• Number Of Pwm Outputs: 1
• On/off Pin: No
• Adjustable Output: No
• Switching Freq: 500kHz
• Operating Supply Voltage (max): 30V
• Operating Temperature Classification: Automotive
• Mounting: Through Hole
• Pin Count: 8
• Package Type: PDIP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-3680; 497-3680-5; 497-3680

High peak currents associated with capacitive loads
necessitate careful grounding techniques. Timing
and bypass capacitors should be connected close
Figure 2: Timing Resistor vs. Oscillator Fre-
Figure 1: Open Loop Test Circuit.
(K )
RT
0.8
50
20
10
5
2
1
10K
ERROR AMP.
V
T
A
i
=15V
ADJUST
=25˚C
20K
4.7K
4.7K
quency
C
T
30K
=5nF
C
T
=10nF
1K
50K
ADJUST
2N2222
D95IN343
I
100K
SENSE
100K
C
T
5K
=2nF
200K 300K
COMP
I
R
SENSE
R
500K
T
T
V
/C
FB
T
D95IN333
f
OSC
1
2
3
4
V
(KHz)
UC2842B
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: Output Dead-Time vs. Oscillator Fre-
50
30
20
10
%
UC2842B/3B/4B/5B - UC3842B/3B/4B/5B
7
6
5
5
3
2
1
10K
V
OUTPUT
GROUND
i
0.1 F
C
20K
T
quency
=200pF
C
T
30K
=500pF
0.1 F
C
T
50K
=1nF
100K
A
C
T
=10nF
1K
1W
C
200K 300K
T
=100pF
C
T
=5nF
C
T
V
V
OUTPUT
GROUND
V
T
=2nF
A
500K fOSC(KHz)
i
=15V
REF
i
=25˚C
D95IN334
5/15