UC2845L-S08-R [UTC]
HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS; 高性能电流模式PWM控制器
| 型号： | UC2845L-S08-R |
| 厂家： | 
Unisonic Technologies |
| 描述： | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLERS |
| 文件： | 总7页 (文件大小：290K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
UNISONIC TECHNOLOGIES CO., LTD
UC2844/45
LINEAR INTEGRATED CIRCUIT
HIGH PERFORMANCE
CURRENT MODE PWM
CONTROLLERS
DESCRIPTION
The UTC UC2844/2845 are high performance fixed frequency
current mode controllers that specifically designed for Off-Line and
DC to DC converter applications with minimal external parts count.
The differences between UC2844 and UC2845 are the maximum
duty cycle ranges and under-voltage lockout thresholds. The
UC2844 ideally suited to off-line applications with UVLO thresholds
of 16V(ON) and 10V(OFF), and UC2845 has UVLO thresholds of
8.5V(ON) and 7.6V(OFF) for lower voltage applications.
*Pb-free plating product number:
UC2844L/UC2845L
FEATURES
* Operation output switching frequency up to 500 kHz
* Output deadtime adjustable from 50% to 70%
* Automatic feed forward compensation
* Latching PWM for cycle-by-cycle current limiting
* High current totem pole output
* Internally trimmed reference with under voltage lockout
* UVLO with hysteresis
* Low startup and operating current
ORDERING INFORMATION
Order Number
Package
Packing
Lead Free
Halogen Free
UC2844L-S08-R
UC2845L-S08-R
UC2844G-S08-R
UC2845G-S08-R
SOP-8
SOP-8
Tape Reel
Tape Reel
www.unisonic.com.tw
Copyright © 2010 Unisonic Technologies Co., Ltd
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QW-R103-051.A
UC2844/45
LINEAR INTEGRATED CIRCUIT
PIN CONFIGURATION
PIN DESCRIPTION
PIN NO
1
PIN NAME
FUNCTION
Compensation Error amplifier output, this pin is made available for loop compensation.
Voltage Feedback, the inverting input of the Error Amplifier. It is normally connected to the
switching power supply output through a resistor divider.
2
3
VFB
A voltage proportional to inductor current is connected to this input. The PWM uses this
information to terminate the output switch conduction.
ISENSE
The Oscillator frequency and maximum output duty cycle are programmed by connecting
resistor RT to Vref and capacitor CT to ground. Operation to 1 MHz is possible.
4
5
6
RT/CT
GND
Power ground.
This output directly drives the gate of a power MOSFET. Peak currents up to 1A are
sourced and sunk by this pin. The output switches at one-half the oscillator frequency.
Positive supply.
Output
7
8
VCC
VREF
Reference output, provides charging current for capacitor CT though resistor RT.
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UC2844/45
LINEAR INTEGRATED CIRCUIT
BLOCK DIAGRAM
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UC2844/45
LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATINGS (Ta=25°C)
PARAMETER
SYMBOL
(ICC+Iz)
IOUT
RATINGS
30
UNIT
mA
A
Total Power Supply and Zener Current
Output Current, Source or Sink (Note 2)
Output Energy (Capacitive Load per cycle)
Current Sense and Voltage feedback Inputs
Error Amp Output Sink Current
Power Dissipation
1.0
W
5.0
μJ
V
VIN
-0.3 ~ +5.5
10
ISINK
mA
mW
°C
PD
862
Junction Temperature
TJ
+150
Operating Junction Temperature
Storage Temperature Range
TJ(OPR)
TSTG
-40 ~ +120
-65 ~ +150
°С
°C
Note:1.Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
2.Maxmum package power dissipation limits must be observed.
THERMAL DATA
PARAMETER
SYMBOL
RATINGS
145
UNIT
Thermal Resistance(Junction-to-Air)
θJA
°C/W
ELECTRICAL CHARACTERISTICS
(Ta=25°C, VCC=15V, RT=10k, CT=3.3nF, -40°C ≤ TA ≤ 120°C, unless otherwise specified)
PARAMETER
REFERENCE SECTION
Reference Output Voltage
Line Regulation
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX UNIT
VREF
△VOUT
△VOUT
IOUT=1.0mA,TJ=25 C
4.95
5.0
2.0
3.0
0.2
5.05
20
V
mV
V
CC=12V ~ 25V
Load Regulation
I
OUT=1.0mA ~ 20mA
25
mV
Temperature Stability
Total Output Variation over Line,
Load, Temperature
tS
mV/°C
VREF
4.9
-30
5.1
V
Output Noise Voltage
Long Term Stability
eN
S
f=10Hz ~ 10kHz, TJ=25°C
TA=125°C for 1000 Hours
50
5
μV
mV
mA
Output Short Circuit Current
OSCILLATOR SECTION
Oscillator Voltage Swing
Discharge Current
ISC
-85
-180
VOSC
1.6
10.8
52
V
IDSG
VOSC=2.0V, TJ=25°C
TJ=25°C,
LOW ≤ TA ≤ THI
mA
47
46
57
60
Frequency
fOSC
kHz
T
Frequency Change with Voltage
Frequency Change with Temperature
ERROR AMPLIFIER SECTION
Voltage Feedback Input
ΔfOSC/ΔV VCC=12V ~ 25V
ΔfOSC/ΔT TLOW ≤ TA ≤ THI
0.2
5.0
1.0
%
%
VFB
VOH
VOUT=2.5V
2.45
5.0
2.50
6.2
0.8
12
2.55
1.1
V
V
High
Output Voltage Swing
Low
RL=15k to ground, VFB=2.3V
RL=15k to VREF, VFB=2.7V
VOUT=1.1V, VFB=2.7V
VOUT=5.0V, VFB=2.3V
VFB=2.7V
VOL
Sink
Output Current
ISINK
2.0
mA
Source
ISOURCE
II(BIAS)
GVO
-0.5
-1.0
-0.1
90
Input Bias Current
-1.0
μA
dB
Open Loop Voltage Gain
Power Supply Rejection Ratio
Unity Gain Bandwidth
VOUT=2.0V ~ 4.0V
VCC=12V ~ 25V
65
60
PSRR
GBW
70
dB
TJ=25°C
0.7
1.0
MHz
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UC2844/45
LINEAR INTEGRATED CIRCUIT
ELECTRICAL CHARACTERISTICS(Cont.)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX UNIT
CURRENT SENSE SECTION
Current Sense Input Voltage Gain
(Note 2 & 3)
GV
2.85
0.9
3.0
1.0
3.15
V/V
V
Maximum Current Sense Input
Threshold (Note 2)
VI(THR)
1.1
-10
Input Bias Current
II(BIAS)
PSRR
-2.0
70
μA
dB
ns
Power Supply Rejection Ratio
Propagation Delay
VCC=12V ~ 25V (Note4)
ISINK=20mA
tPLH(IN/OUT)
150
300
OUTPUT SECTION
0.1
1.6
13.5
13.4
0.1
50
0.4
2.2
Low
High
VOL
VOH
V
V
I
SINK=200mA
ISINK=20mA
SINK=200mA
Output Voltage
13
12
I
Output Voltage with UVLO Activated
Output Voltage Rise Time
VOL(UVLO
)
VCC=6.0V, ISINK=1.0mA
CL=1.0nF,TJ=25°C
CL=1.0nF,TJ=25°C
1.1
150
150
V
tR
tF
ns
ns
Output Voltage Fall Time
50
UNDERVOLTAGE LOCKOUT SECTION
UC2844
Startup Threshold
15
7.8
9.0
7.0
16.0
8.4
17
9.0
VTHR
V
V
UC2845
Minimum Operating
Voltage After Turn-On
PWM SECTION
UC2844
UC2845
10.0
7.6
11.0
8.2
VCC(MIN)
Max
Min
DCMAX
47
30
48
50
0
%
%
Duty Cycle
DCMIN
TOTAL DEVICE
Power Supply Zener Voltage
VZ
ICC=25mA
VCC=6.5V
VCC=14V
36
0.5
12
-
V
UC2845
UC2844
1.0
17
Power Supply Current
(Note 4)
ICC
mA
Note: 1. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient
as possible.
2. This parameter is measured at the latch trip point with VFB=0V.
3. Comparator gain is defined as:
ΔV Output Compensation
AV=
ΔV Current Sense Input
4. Adjust VCC above the startup threshold before setting to 15V.
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UC2844/45
LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS
Timing Resistor vs. Oscillator Frequency
Output Deadtime vs. Oscillator Frequency
1.0nF
75
70
100
50
VCC = 15V
TA = 25℃
2.0nF
5.0nF
20
65
60
55
50
CT = 10nF
10
5.0
2.0
1.0
Note: Output Switches At
One-Half The Oscillator
Frequency
100pF
200pF
500pF
10k
20k
50k
100k 200k
500k 1.0M
10k
20k
50k
100k 200k
500k 1.0M
Oscillator Frequency, IOSC (Hz)
Oscillator Frequency, IOSC (Hz)
Current Sense Input Threshold vs. Error Amp
Output Voltage
Error Amp Open Loop Gain Phase vs. Frequency
VCC = 15V
1.2
1.0
0.8
100
80
0
VOUT = 2.0V ~ 4.0V
30
RL = 100k
TA = 25℃
Gain
TA = 125℃
TA = 25℃
60
60
40
20
90
0.6
0.4
Phase
120
TA = -55℃
0
150
180
0.2
0
VCC = 15V
-20
10
100
1.0k
10k
100k
1.0M 10M
0
2.0
4.0
6.0
8.0
Error Amp Output Voltage, VOUT (V)
Frequency, f (Hz)
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UC2844/45
LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS(Cont.)
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
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