uc3844bvnguc3845bd ON Semiconductor, uc3844bvnguc3845bd Datasheet - Page 6

• Manufacturer Part Number: uc3844bvnguc3845bd
• Description: Current Mode Controller
• Manufacturer: ON Semiconductor

PIN FUNCTION DESCRIPTION
8-Pin
- 2.0
-1.0
3.0
2.0
1.0
1
2
3
4
5
6
7
8
0
0
0
Pin
Ä Ä
2,4,6,13
14-Pin
V
CC
Ä Ä Ä Ä
Ä Ä Ä Ä
Figure 14. Output Cross Conduction
Figure 12. Output Saturation Voltage
10
12
14
11
1
3
5
7
8
9
T
A
Ä Ä Ä
Ä Ä Ä
T
= - 55°C
A
200
= 25°C
Compensation
Current Sense
I
O
versus Load Current
, OUTPUT LOAD CURRENT (mA)
Feedback
Function
Voltage
Ground
Output
Power
R
Ä Ä Ä Ä Ä
Ä Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä Ä
Ä Ä Ä Ä Ä
GND
GND
V
V
NC
T
V
CC
ref
/C
C
Source Saturation
(Load to Ground)
Sink Saturation
(Load to V
T
T
100 ns/DIV
A
= - 55°C
400
UC3844B, UC3845B, UC2844B, UC2845B
CC
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
R
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 C
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 (V
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.
)
T
to V
Ä Ä Ä Ä Ä
Ä Ä Ä Ä Ä
Ä Ä Ä
ref
V
80 ms Pulsed Load
120 Hz Rate
GND
Ä Ä Ä Ä
Ä Ä Ä Ä
CC
600
and capacitor C
= 15 V
T
A
V
C
T
A
CC
= 25°C
L
= 25°C
= 15 pF
= 30 V
http://onsemi.com
800
OH
T
) is set by the voltage applied to this pin. With a separate power source
to ground. Oscillator operation to 1.0 kHz is possible.
6
90
10
%
%
25
20
15
10
5
0
Figure 15. Supply Current versus Supply Voltage
0
Description
Figure 13. Output Waveform
10
V
CC
, SUPPLY VOLTAGE (V)
50 ns/DIV
20
T
through resistor R
Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä
R
C
V
I
T
Sense
A
FB
T
T
= 25°C
= 10 k
= 3.3 nF
= 0 V
30
V
C
T
= 0 V
A
CC
L
= 25°C
= 1.0 nF
= 15 V
T
.
40