UC3845N ON Semiconductor, UC3845N Datasheet - Page 6

• Manufacturer Part Number: UC3845N
• Description: IC CTRLR CURRENT MODE HP 8DIP
• Manufacturer: ON Semiconductor
• Type: High Performance Current Mode Controllersr

Specifications of UC3845N

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 60kHz
• 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: 0°C ~ 70°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Frequency-max: 60kHz
• Output Voltage Range: 4.9 V to 5.1 V
• Input Voltage Range: 30 V
• Operating Temperature Range: 0 C to + 70 C
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: UC3845NOS

PIN FUNCTION DESCRIPTION
8−Pin
1
2
3
4
5
6
7
8
−
−
−
−
Pin
2,4,6,13
14−Pin
Figure 14. Output Cross Conduction
10
12
14
11
1
3
5
7
−
8
9
Compensation
Current Sense
Power Ground
Feedback
Function
Voltage
Output
R
GND
GND
100 ns/DIV
V
V
NC
T
V
CC
ref
/C
C
T
This pin is Error Amplifier output and is made available for loop compensation.
This is the inverting input of the Error Amplifier. It is normally connected to the switching
power supply output through a resistor divider.
A voltage proportional to inductor current is connected to this input. The PWM uses this
information to terminate the output switch conduction.
The Oscillator frequency and maximum Output duty cycle are programmed by connecting
resistor R
This pin is combined control circuitry and power ground (8−pin package only).
This output directly drives the gate of a power MOSFET. Peak currents up to 1.0 A are
sourced and sunk by this pin. The output switches at one−half the oscillator frequency.
This pin is the positive supply of the control IC.
This is the reference output. It provides charging current for capacitor C
This pin is a separate power ground return (14−pin package only) that is connected back to
the power source. It is used to reduce the effects of switching transient noise on the control
circuitry.
The Output high state (V
With a separate power source connection, it can reduce the effects of switching transient
noise on the control circuitry.
This pin is the control circuitry ground return (14−pin package only) and is connected to back
to the power source ground.
No connection (14−pin package only). These pins are not internally connected.
V
C
T
A
CC
L
T
= 255C
= 15 pF
to V
= 30 V
http://onsemi.com
ref
and capacitor C
6
OH
) is set by the voltage applied to this pin (14−pin package only).
25
20
15
10
5
0
0
T
to ground. Operation to 1.0 MHz is possible.
Description
Figure 15. Supply Current versus
10
V
CC
Supply Voltage
, SUPPLY VOLTAGE (V)
20
T
through resistor R
R
C
V
I
T
Sense
30
A
FB
T
T
= 255C
= 10 k
= 3.3 nF
= 0 V
= 0 V
40
T
.