UC284XBD1R2G View Datasheet(PDF) - ON Semiconductor
Part Name
Description
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UC284XBD1R2G Datasheet PDF : 20 Pages
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UC3844B, UC3845B, UC2844B, UC2845B
0
ÄÄÄÄÄÄÄÄÄÄÄÄÄ −1.0
VCC
Source Saturation VCC = 15 V
TA = 25°C (Load to Ground)
80 ms Pulsed Load
120 Hz Rate
ÄÄÄÄÄÄÄÄÄÄÄ − 2.0
ÄÄÄÄ TA = − 55°C
ÄÄÄÄ 3.0
ÄÄÄÄ TA = − 55°C
ÄÄÄÄ ÄÄÄÄ 2.0
TA = 25°C
ÄÄÄÄÄÄÄÄÄ 1.0
Sink Saturation
ÄÄÄÄÄÄÄ (Load to VCC)
GND
0
0
200
400
600
800
I O, OUTPUT LOAD CURRENT (mA)
Figure 12. Output Saturation Voltage
versus Load Current
VCC = 30 V
CL = 15 pF
TA = 25°C
100 ns/DIV
Figure 14. Output Cross Conduction
VCC = 15 V
90
%
CL = 1.0 nF
TA = 25°C
10
%
50 ns/DIV
Figure 13. Output Waveform
25
20
15
10
5
0
ÄÄÄÄ RT = 10 k
CT = 3.3 nF
ÄÄÄÄ VFB = 0 V
ÄÄÄÄ ISense = 0 V
ÄÄÄÄ TA = 25°C
0
10
20
30
40
VCC, SUPPLY VOLTAGE (V)
Figure 15. Supply Current versus Supply Voltage
Pin
8−Pin 14−Pin
1
1
2
3
3
5
Function
Compensation
Voltage
Feedback
Current Sense
4
7
5
6
10
RT/CT
GND
Output
7
12
VCC
8
14
Vref
8
Power
Ground
11
VC
9
2,4,6,13
GND
NC
PIN FUNCTION DESCRIPTION
Description
This pin is the 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
RT to Vref and capacitor CT to ground. Oscillator operation to 1.0 kHz is possible.
This pin is the combined control circuitry and power ground.
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 CT through resistor RT.
This pin is a separate power ground return 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 (VOH) is set by the voltage applied to this pin. 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 and is connected back to the powersource ground.
No connection. These pins are not internally connected.
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