The UC1842/3/4/5 family of control devices provides the necessary features to implement off-line or dc-to-dc fixed frequency current mode control schemes with a minimal external parts count

UC2845

Manufacturer Part NumberUC2845
DescriptionThe UC1842/3/4/5 family of control devices provides the necessary features to implement off-line or dc-to-dc fixed frequency current mode control schemes with a minimal external parts count
ManufacturerTexas Instruments
UC2845 datasheet
 


Specifications of UC2845

TopologyBoost, Flyback, ForwardControl MethodCurrent
Duty Cycle(max)(%)50Frequency(max)(khz)450
Uvlo Thresholds On/off(v)8.4/7.6Pin/package14SOIC, 8PDIP, 8SOIC
Vin(min)(v)7.6Vin(max)(v)30
Regulated Outputs(#)1Operating Temperature Range(c)-40 to 85
1
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THERMAL CHARACTERISTICS
over operating free-air temperature range (unless otherwise noted)
PACKAGE
DIL-8
SOIC-8
SOIC-14
CFP-14
PLCC-20
(1)
data values stated were derived from MIL-STD-1835B.
JC
(2) Specified
(junction to ambient) is for devices mounted to 5 in
JA
range is given, lower values are for 5 in
and 1.3-mm trace widths for non-power packages with 100 x 100-mil probe land area at the end of each trace.
DISSIPATION RATINGS
T
25 C
A
PACKAGE
POWER RATING
W
700 mW
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, these specifications apply for –55 C
UC284X; 0 C
T
70 C for the 384X; V
A
PARAMETER
REFERENCE SECTION
Output Voltage
T
= 25 C, I
J
Line Regulation
12
V
IN
Load Regulation
1
I
20 mA
0
(2) (3)
Temp. Stability
See
Total Output Variation
Line, load, tempature
Output Noise Voltage
10 Hz f
Long Term Stability
T
= 125 C, 1000 Hrs
A
Output Short Circuit
OSCILLATOR SECTION
Initial Accuracy
T
= 25 C
J
Voltage Stability
12
V
CC
Temp. Stability
T
T
MIN
A
Amplitude
V
4 peak-to-peak
PIN
(1) Adjust V
above the start threshold before setting at 15 V.
CC
(2) These parameters, although specified, are not 100% tested in production.
(3) Temperature stability, sometimes referred to as average temperature coefficient, is described by the equation:
V
(max) * VREF (min)
REF
Temp Stability +
TJ(max) * TJ (min)
the appropriate temperature range. Note that the extremes in voltage do not necessarily occur at the extremes in temperature.
(4) Output frequency equals oscillator frequency for the UC1842 and UC1843.
Output frequency is one half oscillator frequency for the UC1844 and UC1845.
J
N
D8
D14
W
Q
2
FR4 PC board with one ounce copper where noted. When resistance
2
. Test PWB was 0.062 in thick and typically used 0.635-mm trace widths for power packages
DERATING FACTOR
T
70 C
A
ABOVE T
25 C
POWER RATING
A
5.5 mW/ C
452 mW
T
125 C for the UC184X; –40 C
A
(1)
= 15 V
; R
= 10 k ; C
= 3.3 nF, T
CC
T
T
UC1842/3/4/5
UC2842/3/4/5
TEST CONDITIONS
MIN
= 1 mA
4.95
O
25 V
(2)
4.9
(2)
10 kHz, T
= 25 C
J
(2)
–30
(4)
47
25 V
(2)
T
MAX
(2)
V
and V
are the maximum and minimum reference voltages measured over
REF(max)
REF(min)
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UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
SLUS223C – APRIL 1997 – REVISED JUNE 2007
JC
JA
(1)
28
125-160
(2)
25
110
(2)
42
84-160
(2)
35
50-120
5.49 C/W
175.4C/W
(2)
34
43-75
T
85 CPO
T
125 C
A
A
WER RATING
POWER RATING
370 mW
150 mW
T
85 C for the
A
= T
.
A
J
UC3842/3/4/5
TYP
MAX
MIN
TYP
MAX
5.00
5.05
4.90
5.00
5.10
6
20
6
20
6
25
6
25
0.2
0.4
0.2
0.4
mV/ C
5.1
4.82
5.18
50
50
5
25
5
25
–100
–180
–30
–100
–180
52
57
47
52
57
0.2%
1%
0.2%
1%
5%
5%
1.7
1.7
UNIT
V
mV
V
V
mV
mA
kHz
V
3