UC2844BN 查看數據表（PDF） - Motorola => Freescale
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UC2844BN Datasheet PDF : 16 Pages
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UC3844B, 45B UC2844B, 45B
Figure 11. Output Saturation Voltage
versus Load Current
0
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ –1.0
VCC
Source Saturation
TA = 25°C (Load to Ground)
VCC = 15 V
80 µs Pulsed Load
120 Hz Rate
– 2.0
ÄÄÄÄÄÄÄÄÄÄÄÄÄ TA = – 55°C
3.0
2.0
1.0
0
TA = – 55°C
ÄÄÄÄ ÄÄÄÄ Sink Saturation
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄ (Load to VCC)
TA = 25°C
Gnd
0
200
400
600
800
I O, OUTPUT LOAD CURRENT (mA)
Figure 13. Output Cross Conduction
VCC = 30 V
CL = 15 pF
TA = 25°C
100 ns/DIV
Figure 12. Output Waveform
VCC = 15 V
90%
CL = 1.0 nF
TA = 25°C
10%
50 ns/DIV
Figure 14. Supply Current versus Supply Voltage
25
20
15
10
5
RT = 10 k
ÄÄÄÄ CT = 3.3 nF
VFB = 0 V
ÄÄÄÄ ISense = 0 V
ÄÄÄÄ TA = 25°C
0
0
10
20
30
40
VCC, SUPPLY VOLTAGE (V)
Pin
8–Pin 14–Pin
1
1
2
3
3
5
Function
Compensation
Voltage
Feedback
Current Sense
4
7
RT/CT
5
Gnd
6
10
Output
7
12
VCC
8
14
Vref
8
Power
Ground
11
VC
9
Gnd
2,4,6,13 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 power source ground.
No connection. These pins are not internally connected.
6
MOTOROLA ANALOG IC DEVICE DATA
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