UNISONIC TECHNOLOGIES CO., LTD
UC3844/45 LINEAR INTEGRATED CIRCUIT
HIGH PERFORMANCE
CURRENT MODE PWM
CONTROLLERS
DESCRIPTION
The UTC UC3844/3845 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 UC3844 and UC3845 are the maximum
duty cycle ranges and under-voltage lockout thresholds. The
UC3844 ideally suited to off-line applications with UVLO thresholds
of 16V
8.5V
FEATURES
(ON)
and 7.6V
(ON)
and 10V
(OFF)
, and UC3845 has UVLO thresholds of
(OFF)
for lower voltage applications.
*Pb-free plating product number:
UC3844L/UC3845L
* 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
Normal Lead Free Plating
UC3844-D08-T UC3844L-D08-T DIP-8 Tube
UC3844-S08-R UC3844L-S08-R SOP-8 Tape Reel
UC3844-S08-T UC3844L-S08-T SOP-8 Tube
UC3845-D08-T UC3845L-D08-T DIP-8 Tube
UC3845-S08-R UC3845L-S08-R SOP-8 Tape Reel
UC3845-S08-T UC3845L-S08-T SOP-8 Tube
Package Packing
www.unisonic.com.tw 1 of 7
Copyright © 2005 Unisonic Technologies Co., Ltd QW-R103-010,C
UC3844/45 LINEAR INTEGRATED CIRCUIT
PIN CONFIGURATION
PIN DESCRIPTION
PIN NO PIN NAME FUNCTION
1 Compensation Error amplifier output, this pin is made available for loop compensation.
2 VFB
3 ISENSE
4 RT/CT
5 GND Power ground.
6 Output
7 VCC Positive supply.
8 V
REF
Voltage Feedback, 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 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.
Reference output, provides charging current for capacitor CT though resistor RT.
to Vref and capacitor CT to ground. Operation to 1 MHz is possible.
T
UNISONIC TECHNOLOGIES CO., LTD 2 of 7
www.unisonic.com.tw QW-R103-010,C
UC3844/45 LINEAR INTEGRATED CIRCUIT
BLOCK DIAGRAM
UNISONIC TECHNOLOGIES CO., LTD 3 of 7
www.unisonic.com.tw QW-R103-010,C
UC3844/45 LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATINGS (Ta=25°C)
PARAMETER SYMBOL RATINGS UNIT
Total Power Supply and Zener Current (ICC+Iz) 30 mA
Output Current, Source or Sink (Note 2) I
Output Energy (Capacitive Load per cycle) W 5.0 μJ
Current Sense and Voltage feedback Inputs VIN -0.3 ~ +5.5 V
Error Amp Output Sink Current I
Power Dissipation
SOP-8 862 mW
DIP-8
Junction Temperature TJ +150 °C
Operation Temperature Range T
Storage Temperature Range T
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 UNIT
Thermal Resistance(Junction-to-Air)
SOP-8 145 °C/W
DIP-8
1.0 A
OUT
10 mA
SINK
PD
OPR
-65 ~ +150 °C
STG
θJA
1250 mW
0 ~ 70 °C
100 °C/W
ELECTRICAL CHARACTERISTICS
(Ta=25°C, VCC=15V, RT=10k, CT=3.3nF, 0°C ≤ TA ≤ 70°C, unless otherwise specified)
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT
REFERENCE SECTION
Reference Output Voltage V
Line Regulation
Load Regulation
△V
△V
I
REF
OUT
OUT
=1.0mA,TJ=25 C 4.9 5.0 5.1 V
OUT
V
=12V ~ 25V 2.0 20 mV
CC
I
=1.0mA ~ 20mA 3.0 25 mV
OUT
Temperature Stability tS 0.2 mV/°C
Total Output Variation over Line,
Load, Temperature
V
REF
4.82 5.18 V
Output Noise Voltage eN f=10Hz ~ kHz, TJ=25°C 50 μV
Long Term Stability S TA=125°C for 1000 Hours 5 mV
Output Short Circuit Current ISC -30 -85 -180 mA
OSCILLATOR SECTION
Oscillator Voltage Swing V
1.6 V
OSC
Discharge Current IDSG VOSC=2.0V, TJ=25°C 10.8 mA
Frequency f
Frequency Change with Voltage Δf
Frequency Change with Temperature Δf
OSC
OSC
OSC
TJ=25°C, 47 52 57
0°C
≤ T
≤ 70°C
A
46 60
kHz
/ΔV VCC=12V ~ 25V 0.2 1.0 %
0°C
≤ T
/ΔT
≤ 70°C
A
5.0 %
ERROR AMPLIFIER SECTION
Voltage Feedback Input VFB V
Output Voltage Swing
Output Current
Input Bias Current I
High VOH RL=15k to ground, VFB=2.3V 5.0 6.2
Low VOL RL=15k to V
Sink I
Source I
V
SINK
V
SOURCE
VFB=2.7V -0.1 -2.0 μA
I(BIAS)
Open Loop Voltage Gain GVO V
=2.5V 2.42 2.50 2.58 V
OUT
, VFB=2.7V 0.8 1.1
REF
=1.1V, VFB=2.7V 2.0 12
OUT
=5.0V, VFB=2.3V -0.5 -1.0
OUT
=2.0V ~ 4.0V 65 90 dB
OUT
V
mA
Power Supply Rejection Ratio PSRR VCC=12V ~ 25V 60 70 dB
Unity Gain Bandwidth GBW TJ=25°C 0.7 1.0 MHz
UNISONIC TECHNOLOGIES CO., LTD 4 of 7
www.unisonic.com.tw QW-R103-010,C
UC3844/45 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)
Maximum Current Sense Input
Threshold (Note 2)
Input Bias Current I
G
V
I(THR)
I(BIAS)
Power Supply Rejection Ratio PSRR VCC=12V ~ 25V (Note4) 70 dB
Propagation Delay t
PLH(IN/OUT)
OUTPUT SECTION
Low VOL
Output Voltage
Output Voltage with U
High V
Activated VOL(U
VLO
OH
Output Voltage Rise Time tR C
Output Voltage Fall Time tF C
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold
Voltage After Turn-On
UC3844 14.5 16.0 17.5
UC3845
UC3844 8.5 10.0 11.5Minimum Operating
UC3845
V
V
CC(MIN)
THR
PWM SECTION
Duty Cycle
Max DCMAX 47 48 50 %
Min DC
TOTAL DEVICE
Power Supply Zener Voltage VZ ICC=25mA 30 36 - V
Power Supply Current
(Note 4)
UC3845 VCC=6.5V 0.5 1.0
UC3844
I
CC
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 V
3. Comparator gain is defined as: ΔV Output Compensation
A
=
V
ΔV Current Sense Input
4. Adjust V
above the startup threshold before setting to 15V.
CC
V
2.85 3.0 3.15 V/V
0.9 1.0 1.1 V
-2.0 -10 μA
150 300 ns
I
=20mA 0.1 0.4
SINK
I
=200mA 1.6 2.2
SINK
I
=20mA
SINK
I
=200mA 12 13.4
SINK
)VCC=6.0V, I
VLO
=1.0nF,TJ=25°C 50 150 ns
L
=1.0nF,TJ=25°C 50 150 ns
L
7.8 8.4 9.0
7.0 7.6 8.2
MIN 0 %
V
CC
=14V
=1.0mA 0.1 1.1 V
SINK
=0V.
FB
13 13.5
12 17
V
V
V
V
mA
UNISONIC TECHNOLOGIES CO., LTD 5 of 7
www.unisonic.com.tw QW-R103-010,C
UC3844/45 LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS
100
50
20
(kΩ)
T
10
5.0
Timing Resistor, R
2.0
1.0
100
(dB)
V
Open Loop Voltage Gain, G
Timing Resistor vs. Oscillator Frequency
1
0
2
0
0
p
5
F
0
0
p
F
1
.
0
n
2
F
.
0
n
F
5
.
0
n
F
C
T
=
1
0
n
F
Note: Output Switches At
One-Half The Oscillator
Frequency
10k 20k 50k 100k
Oscillator Frequency, I
200k 500k 1.0M
(Hz)
OSC
Error Amp Open Loop Gain Phase vs. Frequency
VCC= 15V
V
= 2.0V ~ 4.0V
80
Gain
OUT
RL= 100k
= 25℃
T
A
60
40
20
0
0
p
VCC= 15V
T
A
F
Phase
= 25℃
0
30
60
90
120
150
Output Deadtime vs. Oscillator Frequency
75
1.0nF
70
2.0nF
5.0nF
65
CT= 10nF
60
55
Percent Output Deadtime, DT (%)
50
10k 20k 50k 100k
Oscillator Frequency, I
200k 500k 1.0M
OSC
500pF
(Hz)
100pF
200pF
Current Sense Input Threshold vs. Error Amp
1.2
1.0
0.8
TA= 25℃
0.6
0.4
Excess Phase Degrees, φ
0.2
Output Voltage
TA= 125℃
TA= -55℃
VCC= 15V
-20
10 100 1.0k 10k
Frequency, f (Hz)
100k 1.0M 10M
180
Current Sense Input Threshold, VIN(THR) (V)
0
02.04.0
Error Amp Output Voltage, V
6.0 8.0
(V)
OUT
UNISONIC TECHNOLOGIES CO., LTD 6 of 7
www.unisonic.com.tw QW-R103-010,C
UC3844/45 LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS(Cont.)
(V)
O(SAT)
Output Saturation Voltage, V
(mA)
CC
Supply Current, I
UCX845
UCX844
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 believ ed to be accurate
and reliable and may be changed without notice.
UNISONIC TECHNOLOGIES CO., LTD 7 of 7
www.unisonic.com.tw QW-R103-010,C
Loading...