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UC3843T の電気的特性と機能

UC3843TのメーカーはSTMicroelectronicsです、この部品の機能は「(UC3842T - UC3845T) HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER」です。


製品の詳細 ( Datasheet PDF )

部品番号 UC3843T
部品説明 (UC3842T - UC3845T) HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER
メーカ STMicroelectronics
ロゴ STMicroelectronics ロゴ 




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UC3843T Datasheet, UC3843T PDF,ピン配置, 機能
www.DataSheet4U.com
UC3842T UC3843T
® UC3844T UC3845T
HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER
. TRIMMED OSCILLATOR FOR PRECISE FRE-
QUENCY CONTROL
. OSCILLATOR FREQUENCY GUARANTEED
AT 250kHz
. CURRENT MODE OPERATION TO 500kHz
. AUTOMATIC FEED FORWARD COMPENSA-
TION
. LATCHING PWM FOR CYCLE-BY-CYCLE
CURRENT LIMITING
. INTERNALLY TRIMMED REFERENCE WITH
UNDERVOLTAGE LOCKOUT
. HIGH CURRENT TOTEM POLE OUTPUT
. UNDERVOLTAGE LOCKOUT WITH HYSTER-
ESIS
. LOW START-UP AND OPERATING CURRENT
DESCRIPTION
The UC384XT family of control ICs provides the
necessary features to implement off-line or DC to
DC fixed frequency current mode control schemes
with a minimal external parts count. Internally imple-
mented circuits include a trimmed oscillator for pre-
cise DUTY CYCLE CONTROL under voltage lock-
out featuring start-up current less than 0.5mA, a pre-
cision reference trimmed for accuracy at the error
amp input, logic to insure latched operation, a PWM
Minidip
SO8
comparator which also provides current limit control,
and a totem pole output stage designed to source
or sink high peak current. The output stage, suitable
for driving N-Channel MOSFETs, is low in the off-
state.
Differences between members of this family are the
under-voltage lockout thresholds and maximum duty
cycle ranges. The UC3842T and UC3844T have
UVLO thresholds of 16V (on) and 10V (off), ideally
suited to off-line applications The corresponding
thresholds for the UC3843T and UC3845T are 8.5 V
and 7.9 V. The UC3842T and UC3843T can operate
to duty cycles approaching 100%. A range of zero to
< 50 % is obtained by the UC3844T and UC3845T by
the addition of an internal toggle flip flop which blanks
the output off every other clock cycle.
BLOCK DIAGRAM (toggle flip flop used only in UC3844T and UC3845T)
7
Vi
5
GROUND
4
RT/CT
VFB
COMP
CURRENT
SENSE
2
1
3
34V UVLO
S/R
5V
REF
2.50V
VREF GOOD
LOGIC
INTERNAL
BIAS
OSC
ERROR AMP.
+
-
2R
R
T
S
R
1V
CURRENT
SENSE
COMPARATOR
PWM
LATCH
8 VREF
5V 50mA
6
OUTPUT
D95IN331
September 2001
1/15

1 Page





UC3843T pdf, ピン配列
THERMAL DATA
Symbol
Description
Rth j-amb Thermal Resistance Junction-ambient.
www.DataSheet4U.com
U3842T - UC3843T - UC3844T - UC3845T
Minidip
max. 100
SO8
150
Unit
°C/W
ELECTRICAL CHARACTERISTICS ( [note 1] Unless otherwise stated, these specifications apply for
0 < Tamb < 105°C; Vi = 15V (note 5); RT = 10K; CT = 3.3nF)
Symbol
Parameter
REFERENCE SECTION
VREF Line Regulation
VREF Load Regulation
VREF/T Temperature Stability
Total Output Variation
eN Output Noise Voltage
Long Term Stability
ISC Output Short Circuit
OSCILLATOR SECTION
fOSC Frequency
fOSC/V Frequency Change with Volt.
fOSC/T Frequency Change with Temp.
VOSC Oscillator Voltage Swing
Idischg Discharge Current (VOSC =2V)
ERROR AMP SECTION
V2 Input Voltage
Ib Input Bias Current
AVOL
BW Unity Gain Bandwidth
PSRR Power Supply Rejec. Ratio
Io Output Sink Current
Io Output Source Current
VOUT High
VOUT Low
CURRENT SENSE SECTION
GV Gain
V3 Maximum Input Signal
SVR Supply Voltage Rejection
Ib Input Bias Current
Delay to Output
Test Conditions
Value
Unit
Min. Typ. Max.
12V Vi 25V
1 Io 20mA
(Note 2)
Line, Load, Temperature
10Hz f 10KHz Tj = 25°C
(note 2)
Tamb = 125°C, 1000Hrs (note 2)
4.85
-30
2
3
0.2
50
5
-100
20 mV
25 mV
mV/°C
5.15 V
µV
25
-180
mV
mA
Tj = 25°C
TA = Tlow to Thigh
TJ = 25°C (RT = 6.2k, CT = 1nF)
VCC = 12V to 25V
TA = Tlow to Thigh
(peak to peak)
TA = Tlow to Thigh
49 52 55 KHz
48 – 56 KHz
225 250 275 KHz
– 0.2 1 %
– 1 –%
– 1.6 – V
7.3 – 8.8 mA
VPIN1 = 2.5V
VFB = 5V
2V Vo 4V
TJ = 25°C
12V Vi 25V
VPIN2 = 2.7V VPIN1 = 1.1V
VPIN2 = 2.3V VPIN1 = 5V
VPIN2 = 2.3V;
RL = 15Kto Ground
VPIN2 = 2.7V;
RL = 15Kto Pin 8
(note 3 & 4)
VPIN1 = 5V (note 3)
12 Vi 25V (note 3)
2.42 2.50 2.58 V
-0.1 -2 µA
65 90
dB
0.7 1
MHz
60 70
dB
2 12
mA
-0.5 -1
mA
5 6.2
V
0.8 1.1 V
2.85 3 3.15 V/V
0.9 1 1.1 V
70 dB
-2 -10 µA
100 300 ns
3/15


3Pages


UC3843T 電子部品, 半導体
UC3842T - UC3843T - UC3844T - UC3845T
www.DataSheet4U.com
Figure 4: Oscillator Discharge Current vs. Tem-
perature.
Idischg
(mA)
8.5
D95IN335
Vi=15V
VOSC=2V
8.0
7.5
7.0
-55 -25 0 25 50 75 100 TA(˚C)
Figure 6: Error Amp Open-Loop Gain and
Phase vs. Frequency.
(dB)
D95IN337 φ
Vi=15V
80
Gain
VO=2V to 4V
RL=100K
TA=25˚C
30
60 60
40 90
Phase
20 120
0 150
-20 180
10 100 1K 10K 100K 1M f(Hz)
Figure 8: Reference Voltage Change vs.
Source Current.
D95IN339
60
Vi=15V
50
40 TA=-40˚C
TA=125˚C
30
20
10
0
0
6/15
20 40 60 80 100 Iref(mA)
Figure 5: Maximum Output Duty Cycle vs. Tim-
ing Resistor.
Dmax
(%)
D95IN336
90
Idischg=7.5mA
80
Idischg=8.8mA
70
60
Vi=15V
CT=3.3nF
50 TA=25˚C
40
0.8 1
23
5 RT(K)
Figure 7: Current Sense Input Threshold vs. Er-
ror Amp Output Voltage.
Vth
(V)
Vi=15V
D95IN338
1.0
TA=25˚C
0.8
TA=125˚C
0.6
0.4
TA=-40˚C
0.2
0.0
0 2 4 6 VO(V)
Figure 9: Reference Short Circuit Current vs.
Temperature.
ISC
(mA)
100
D95IN340
Vi=15V
RL0.1
90
80
70
60
50
-55 -25 0 25 50 75 100 TA(˚C)

6 Page



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