UC2846M [TI]
Current Mode PWM Controller;
| 型号： | UC2846M |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | Current Mode PWM Controller |
| 文件： | 总8页 (文件大小：465K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
UC1846/7
UC2846/7
UC3846/7
Current Mode PWM Controller
FEATURES
DESCRIPTION
•
Automatic Feed Forward Compensation
The UC1846/7 family of control ICs provides all of the necessary
features to implement fixed frequency, current mode control
schemes while maintaining a minimum external parts count. The su-
perior performance of this technique can be measured in improved
line regulation, enhanced load response characteristics, and a sim-
pler, easier-to-design control loop. Topological advantages include
inherent pulse-by-pulse current limiting capability, automatic sym-
metry correction for push-pull converters, and the ability to parallel
“power modules" while maintaining equal current sharing.
•
Programmable Pulse-by-Pulse Current
Limiting
•
Automatic Symmetry Correction in Push-pull
Configuration
•
•
Enhanced Load Response Characteristics
Parallel Operation Capability for Modular
Power Systems
Protection circuitry includes built-in under-voltage lockout and pro-
grammable current limit in addition to soft start capability. A shut-
down function is also available which can initiate either a complete
shutdown with automatic restart or latch the supply off.
•
Differential Current Sense Amplifier with
Wide Common Mode Range
•
•
•
•
•
•
•
Double Pulse Suppression
500mA (Peak) Totem-pole Outputs
±1% Bandgap Reference
Under-voltage Lockout
Soft Start Capability
Other features include fully latched operation, double pulse sup-
pression, deadline adjust capability, and a ±1% trimmed bandgap
reference.
The UC1846 features low outputs in the OFF state, while the
UC1847 features high outputs in the OFF state.
Shutdown Terminal
500kHZ Operation
BLOCK DIAGRAM
1/97
UC1846/7
UC2846/7
UC3846/7
ABSOLUTE MAXIMUM RATINGS (Note 1)
Supply Voltage (Pin 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V
Collector Supply Voltage (Pin 13). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V
Output Current, Source or Sink (Pins 11, 14). . . . . . . . . . . . . . . . . . . . . . . . 500mA
Analog Inputs (Pins 3, 4, 5, 6, 16) . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +VIN
Reference Output Current (Pin 2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30mA
Sync Output Current (Pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5mA
Error Amplifier Output Current (Pin 7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5mA
Soft Start Sink Current (Pin 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA
Oscillator Charging Current (Pin 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA
Power Dissipation at TA=25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW
Power Dissipation at TC=25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000mW
Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65°C to +150°C
Lead Temperature (soldering, 10 seconds. . . . . . . . . . . . . . . . . . . . . . . . . +300°C
Note 1. All voltages are with respect to Ground, Pin 13. Currents are positive into,
negative out of the speficied terminal. Consult Packaging Section of Databook for
thermal limitations and considerations of packages. Pin numbers refer to DIL and
SOIC packages only.
CONNECTION DIAGRAMS
DIL-16, SOIC-16
(TOP VIEW)
J or N Package, DW Package
PLCC-20, LCC-20
(TOP VIEW)
Q, L Packages
PACKAGE PIN FUNCTION
FUNCTION
PIN
1
N/C
C/L SS
VREF
C/S-
C/S+
N/C
2
3
4
5
6
E/A+
E/A-
Comp
CT
N/C
RT
Sync
A Out
Gnd
N/C
VC
7
8
9
10
11
12
13
14
15
16
17
18
19
20
B Out
VIN
Shutdown
(Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for
UC1846/7; -40°C to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7;
VIN=15V, RT=10k, CT=4.7nF, TA=TJ.)
ELECTRICAL CHARACTERISTICS
UC1846/UC1847
UC3846/UC3847
PARAMETER
TEST CONDITIONS
UC2846/UC2847
MIN. TYP. MAX. MIN. TYP. MAX. UNITS
Reference Section
Output Voltage
TJ=25°C, IO=1mA
5.05
5.10
5
5.15
20
5.00
5.10
5
5.20
20
V
mV
mV
mV/°C
V
Line Regulation
VIN=8V to 40V
Load Regulation
IL=1mA to 10mA
3
15
3
15
Temperature Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Over Operating Range, (Note 2)
Line, Load, and Temperature (Note 2)
10Hz≤ f ≤10kHz, TJ=25°C (Note 2)
TJ=125°C, 1000 Hrs. (Note 2)
0.4
0.4
5.00
-10
5.20
4.95
-10
5.25
100
5
100
5
µV
mV
mA
Short Circuit Output Current VREF=0V
-45
-45
2
UC1846/7
UC2846/7
UC3846/7
(Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C
to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; VIN=15V, RT=10k, CT=4.7nF,
TA=TJ.)
ELECTRICAL
CHARACTERISTICS (cont.)
UC1846/UC1847
UC3846/UC3847
PARAMETER
TEST CONDITIONS
UC2846/UC2847
MIN. TYP. MAX. MIN. TYP. MAX. UNITS
Oscillator Section
Initial Accuracy
TJ=25°C
VIN=8V to 40V
39
43
-1
47
2
39
43
-1
47
2
kHz
%
%
V
Voltage Stability
Temperature Stability
Sync Output High Level
Sync Output Low Level
Sync Input High Level
Sync Input Low Level
Sync Input Current
Error Amp Section
Input Offset Voltage
Input Bias Current
Input Offset Current
Common Mode Range
Open Loop Voltage Gain
Unity Gain Bandwidth
CMRR
Over Operating Range (Note 2)
-1
-1
3.9
3.9
4.35
2.3
3.9
3.9
4.35
2.3
2.5
2.5
V
Pin 8=0V
V
Pin 8=0V
2.5
1.5
2.5
1.5
V
Sync Voltage=3.9V, Pin 8=0V
1.3
1.3
mA
0.5
-0.6
40
5
-1
0.5
-0.6
40
10
-2
mV
µA
nA
V
250
250
VIN=8V to 40V
0
80
0.7
75
80
2
VIN-2V
0
80
0.7
75
80
2
VIN-2V
∆VO=1.2 to 3V, VCM=2V
TJ=25°C (Note 2)
105
1.0
100
105
6
105
1.0
100
105
6
dB
MHz
dB
dB
mA
mA
V
VCM=0V to 38V, VIN=40V
VIN=8V to 40V
PSRR
Output Sink Current
Output Source Current
High Level Output Voltage
Low Level Output Voltage
VID=-15mV to -5V, VPIN 7=1.2V
VID=15mV to 5V, VPIN 7=2.5V
RL=(Pin 7) 15kΩ
-0.4
4.3
-0.5
4.6
0.7
-0.4
4.3
-0.5
4.6
0.7
1
1
V
Current Sense Amplifier Section
Amplifier Gain
VPIN 3=0V, Pin 1 Open (Notes 3 & 4)
2.5
1.1
2.75
3.0
2.5
1.1
2.75
3.0
V
Maximum Differential Input Pin 1 Open (Note 3)
Signal (VPIN 4-VPIN 3)
Input Offset Voltage
CMRR
RL (Pin 7)=15kW
1.2
5
1.2
5
V
mV
dB
dB
µA
µA
V
VPIN 1=0.5V, Pin 7 Open (Note 3)
VCM=1V to 12V
25
25
60
60
83
60
60
83
PSRR
VIN=8V to 40V
84
84
Input Bias Current
Input Offset Current
Input Common Mode Range
Delay to Outputs
VPIN 1=0.5V, Pin 7 Open (Note 3)
VPIN 1=0.5V, Pin 7 Open (Note 3)
-2.5
0.08
-10
1
-2.5
0.08
-10
1
0
VIN-3
500
0
VIN-3
500
TJ=25°C, (Note 2)
200
200
ns
Current Limit Adjust Section
Current Limit Offset
VPIN 3=0V, VPIN 4=0V, Pin 7 Open
(Note 3)
0.45
0.5
-10
0.55
-30
0.45
0.5
-10
0.55
-30
V
Input Bias Current
Shutdown Terminal Section
Threshold Voltage
VPIN 5=VREF, VPIN 6=0V
µA
250
0
350
1.5
400
VIN
250
0
350
1.5
400
VIN
mV
V
Input Voltage Range
Minimum Latching Current (Note 6)
(IPIN 1)
3.0
3.0
mA
3
UC1846/7
UC2846/7
UC3846/7
(Unless otherwise stated, these specifications apply for TA=-55°C to +125°C for UC1846/7; -40°C
to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; VIN=15V, RT=10k, CT=4.7nF,
TA=TJ.)
ELECTRICAL
CHARACTERISTICS (cont.)
UC1846/UC1847
UC3846/UC3847
PARAMETER
TEST CONDITIONS
UC2846/UC2847
MIN. TYP. MAX. MIN. TYP. MAX. UNITS
Shutdown Terminal Section (cont.)
Maximum Non-Latching
Current (IPIN 1)
(Note 7)
1.5
0.8
1.5
0.8
mA
ns
Delay to Outputs
TJ=25°C (Note 2)
300
600
300
600
Output Section
Collector-Emitter Voltage
40
40
V
µA
V
Collector Leakage Current VC=40V (Note 5)
200
0.4
2.1
200
0.4
2.1
Output Low Level
Output High Level
ISINK=20mA
0.1
0.4
0.1
0.4
ISINK=100mA
V
ISOURCE=20mA
13
12
13.5
13.5
50
13
12
13.5
13.5
50
V
ISOURCE=100mA
V
Rise Time
Fall Time
CL=1nF, TJ=25°C (Note 2)
CL=1nF, TJ=25°C (Note 2)
300
300
300
300
ns
ns
50
50
Under-Voltage Lockout Section
Start-Up Threshold
7.7
8.0
7.7
8.0
V
V
Threshold Hysteresis
Total Standby Current
Supply Current
0.75
0.75
17
21
17
21
mA
Note 2. These parameters, although guaranteed over the recommended operating conditions, are not 100% tested in production.
Note 3. Parameter measured at trip point of latch with VPIN 5 = VREF, VPIN 6 = 0V.
Note 4. Amplifier gain defined as:
G = ∆ VPIN 7; ∆ VPIN 4 = 0 to 1.0V.
∆ VPIN 4
Note 5. Applies to UC1846/UC2846/UC3846 only due to polarity of outputs.
Note 6. Current into Pin 1 guaranteed to latch circuit in shutdown state.
Note 7. Current into Pin 1 guaranteed not to latch circuit in shutdown state.
APPLICATIONS DATA
Oscillator Circuit
ID
Output deadtime is determined by the external capacitor, CT, according to the formula: τd (µs) = 145CT (µf )
.
3.6
RT (kΩ)
ID −
ID = Oscillator discharge current at 25°C is typically 7.5.
For large values of RT: τd (µs) ≈ 145CT (µf ).
2.2
Oscillator frequency is approximated by the formula: fT (kHz) ≈
.
RT (kΩ)• CT (µf )
4
UC1846/7
UC2846/7
UC3846/7
APPLICATIONS DATA (cont.)
Error Amp Gain and Phase vs Frequency
Error Amp Output Configuration
Error Amp Open-Logic D.C. Gain vs Load Resistance
Parallel Operation
5
UC1846/7
UC2846/7
UC3846/7
APPLICATIONS DATA (cont.)
Pulse by Pulse Current Limiting
R2 VREF
R1 + R2
− 0.5
Peak Current (IS) is determined by the formula: IS =
3RS
Soft Start and Shutdown /Restart Functions
6
UC1846/7
UC2846/7
UC3846/7
APPLICATIONS DATA (cont.)
Current Sense Amp Connection
A small RC filter may be required in some applications to reduce switch transients.
Differential input allows remote, noise free sensing.
UC1846 Open Loop Test Circuit
UNITRODE CORPORATION
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603)424-3460
7
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