|
|
|
UC2844 Schematic ( PDF Datasheet ) - ON Semiconductor
| Teilenummer | UC2844 |
|
| Beschreibung | (UC2844 / UC2845) High Performance Current Mode Controllers | |
| Hersteller | ON Semiconductor | |
| Logo |  |
|
Gesamt 16 Seiten 
UC3844, UC3845, UC2844,
UC2845
High Performance
Current Mode Controllers
The UC3844, UC3845 series are high performance fixed frequency
current mode controllers. They are specifically designed for Off−Line
and DC−to−DC converter applications offering the designer a cost
effective solution with minimal external components. These integrated
circuits feature an oscillator, a temperature compensated reference, high
gain error amplifier, current sensing comparator, and a high current
totem pole output ideally suited for driving a power MOSFET.
Also included are protective features consisting of input and
reference undervoltage lockouts each with hysteresis, cycle−by−cycle
current limiting, a latch for single pulse metering, and a flip−flop which
blanks the output off every other oscillator cycle, allowing output dead
times to be programmed for 50% to 70%.
These devices are available in an 8−pin dual−in−line plastic package
as well as the 14−pin plastic surface mount (SOIC−14). The SOIC−14
package has separate power and ground pins for the totem pole output
stage.
The UCX844 has UVLO thresholds of 16 V (on) and 10 V (off),
ideally suited for off−line converters. The UCX845 is tailored for
lower voltage applications having UVLO thresholds of 8.5 V (on) and
7.6 V (off).
Features
• Current Mode Operation to 500 kHz Output Switching Frequency
• Output Deadtime Adjustable from 50% to 70%
• Automatic Feed Forward Compensation
• Latching PWM for Cycle−By−Cycle Current Limiting
• Internally Trimmed Reference with Undervoltage Lockout
• High Current Totem Pole Output
• Input Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
• Direct Interface with ON Semiconductor SENSEFETt Products
• Pb−Free Packages are Available
VCC 7(12)
Vref
8(14)
RTCT
4(7)
Voltage
Feedback
2(3)
1(1)
Output
Comp.
R
5.0V
Reference
VCC
Undervoltage
Lockout
R
Vref
Undervoltage
Lockout
Oscillator
+
−
Error
Amplifier
Flip
Flop
&
Latching
PWM
GND 5(9)
Pin numbers in parenthesis are for the D suffix SOIC−14 package.
Figure 1. Simplified Block Diagram
VC
7(11)
Output
6(10)
PWR GND
5(8)
Current
Sense
3(5)
© Semiconductor Components Industries, LLC, 2006
July, 2006 − Rev. 7
1
http://onsemi.com
8
1
14
1
8
1
PDIP−8
N SUFFIX
CASE 626
SOIC−14
D SUFFIX
CASE 751A
SOIC−8
D1 SUFFIX
CASE 751A
PIN CONNECTIONS
Compensation 1
Voltage Feedback 2
Current Sense 3
RT/CT 4
8 Vref
7 VCC
6 Output
5 GND
(Top View)
Compensation 1
NC 2
Voltage Feedback 3
NC 4
Current Sense 5
NC 6
RT/CT 7
14 Vref
13 NC
12 VCC
11 VC
10 Output
9 GND
8 Power Ground
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 14 of this data sheet.
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page page 14 of this data sheet.
Publication Order Number:
UC3844/D
 
UC3844, UC3845, UC2844, UC2845
VCC = 30 V
CL = 15 pF
TA = 255C
100 ns/DIV
Figure 14. Output Cross Conduction
25
20
15
10 RT = 10 k
CT = 3.3 nF
VFB = 0 V
5 ISense = 0 V
TA = 255C
0
0 10 20 30 40
VCC, SUPPLY VOLTAGE (V)
Figure 15. Supply Current versus
Supply Voltage
PIN FUNCTION DESCRIPTION
Pin
8−Pin 14−Pin
Function
1 1 Compensation
23
Voltage
Feedback
3 5 Current Sense
47
5−
6 10
RT/CT
GND
Output
7 12
VCC
8 14
Vref
− 8 Power Ground
− 11
−9
− 2,4,6,13
VC
GND
NC
Description
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 RT to Vref and capacitor CT to ground. Operation to 1.0 MHz is possible.
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 CT through resistor RT.
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 (VOH) is set by the voltage applied to this pin (14−pin package only).
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.
http://onsemi.com
6
6 Page 
UC3844, UC3845, UC2844, UC2845
115VA
C
4.7W
MDA
+
250
202
56k
8(14)
0.01
33k
4(7)
1.0nF
18k
2(3)
4.7k
Bias
OSC
+
+
−
EA
5.0Vref
+
+−
7(12)
+
−+
T
S
−
+
Q
R
Comp/Latch
4.7k
1N4935
+
68
100
1N4937
3300pF
MBR1635 L1
T1 +
2200 1000
1N4935
+
47
MUR110
+ L2
1000 10
1000 10
+
MUR110
680pF
L3
5.0V/4.0A
+
5.0V RTN
+ 12V/0.3A
±12V RTN
+
−12V/0.3A
7(11)
22W
6(10)
1N5819
5(8)
3(5) 1.0k
2.7k
MTP
4N50
1N4937
1(1)
5(9)
470pF
0.5W
T1 − Primary: 45 Turns # 26 AWG
T1 − Secondary ±12 V: 9 Turns # 30 AWG
T1 − (2 strands) Bifiliar Wound
T1 − Secondary 5.0 V: 4 Turns (six strands)
T1 − #26 Hexfiliar Wound
T1 − Secondary Feedback: 10 Turns #30 AWG
T1 − (2 strands) Bifiliar Wound
T1 − Core: Ferroxcube EC35−3C8
T1 − Bobbin: Ferroxcube EC35PCB1
T1 − Gap ≈0.01" for a primary inductance of 1.0 mH
L1 − 15 mH at 5.0 A, Coilcraft Z7156.
L2, L3 − 25 mH at 1.0 A, Coilcraft Z7157.
Figure 30. 27 Watt Off−Line Flyback Regulator
Test Conditions
Line Regulation: 5.0 V Vin = 95 VAC to 130 VAC
± 12 V
Load Regulation: 5.0 V
± 12 V
Vin = 115 VAC, Iout = 1.0 A to 4.0 A
VmiAn = 115 VAC, Iout = 100 mA to 300
Output Ripple:
5.0 V Vin = 115 VAC
± 12 V
Efficiency
Vin = 115 VAC
All outputs are at nominal load currents, unless otherwise noted.
Results
D = 50 mV or ±0.5%
D = 24 mV or ±0.1%
D = 300 mV or ±3.0%
D = 60 mV or ±0.25%
40 mVpp
80 mVpp
70%
http://onsemi.com
12
12 Page | ||
| Seiten | Gesamt 16 Seiten | |
| PDF Download | [ UC2844 Schematic.PDF ] | |
Link teilen
Besondere Datenblatt
| Teilenummer | Beschreibung | Hersteller |
| UC2840 | PWM Controller |  Unitrode |
| UC2840 | PWM Controller |  ST Microelectronics |
| UC2841 | Programmable Off-Line PWM Controller |  Texas Instruments |
| UC2842 | Current Mode PWM Controller (Rev. C) | Texas Instruments |
| UC2842 | (UC2843 / UC2844 / UC2845) CURRENTMODE PWM CONTROLLER | ST Microelectronics |
| Teilenummer | Beschreibung | Hersteller |
| CD40175BC | Hex D-Type Flip-Flop / Quad D-Type Flip-Flop. |
 Fairchild Semiconductor |
| KTD1146 | EPITAXIAL PLANAR NPN TRANSISTOR. |
 KEC |
| www.Datenblatt-PDF.com | 2020 | Kontakt | Suche |