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UC3845B の電気的特性と機能

UC3845BのメーカーはST Microelectronicsです、この部品の機能は「(UC3842B - UC3845B) HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER」です。


製品の詳細 ( Datasheet PDF )

部品番号 UC3845B
部品説明 (UC3842B - UC3845B) HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER
メーカ ST Microelectronics
ロゴ ST Microelectronics ロゴ 




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UC3845B Datasheet, UC3845B PDF,ピン配置, 機能
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UC2842B/3B/4B/5B
® UC3842B/3B/4B/5B
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
TheUC384xB family ofcontrolICs providesthe nec-
essary 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-
outfeaturingstart-up current less than0.5mA,a pre-
cision reference trimmed for accuracy at the error
amp input, logicto insure latched operation,a PWM
Minidip
SO8
comparatorwhich alsoprovidescurrent limit control,
and a totem pole output stage designed to source
or sink high peakcurrent. The outputstage, suitable
for driving N-Channel MOSFETs, is low in the off-
state.
Differences between members of this family are the
under-voltagelockout thresholds and maximum duty
cycle ranges. The UC3842B and UC3844B have
UVLO thresholds of 16V (on) and 10V (off), ideally
suited off-line applications The corresponding thresh-
oldsforthe UC3843BandUC3845Bare8.5 V and7.9
V. The UC3842B and UC3843B can operate to duty
cycles approaching 100%. A range of the zero to <
50 % is obtained by the UC3844B and UC3845B by
the addition of an internal toggle flip flopwhich blanks
the output off every otherclock cycle.
BLOCK DIAGRAM (toggle flip flop used only in UC3844B and UC3845B)
7
Vi
5
GROUND
4
RT/CT
VFB
COMP
CURRENT
SENSE
2
1
3
34V UVLO
S/R
5V
REF
2.50V
OSC
VREF GOOD
LOGIC
INTERNAL
BIAS
T
8 VREF
5V 50mA
6
OUTPUT
ERROR AMP.
+
-
2R
R
S
R
1V
CURRENT
SENSE
COMPARATOR
PWM
LATCH
UC3842B
D95IN331
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UC3845B pdf, ピン配列
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THERMAL DATA
Symbo l
Description
Rth j-amb Thermal Resistance Junction-ambient.
UC2842B/3B/4B/5B - UC3842B/3B/4B/5B
Minidip
max.
100
SO8
150
Unit
°C/W
ELECTRICAL CHARACTERISTICS ( [note 1] Unless otherwise stated, these specifications apply for
-25 < Tamb < 85°C for UC284XB; 0 < Tamb < 70°C for UC384XB; Vi = 15V (note 5); RT = 10K; CT = 3.3nF)
Symbol
P a ram et er
REFERENCE SECTION
T est Cond it ion s
UC 284 X B
UC384XB
Uni t
Min. Typ. Max. Min. Typ. Max.
VREF Output Voltage
Tj = 25°C Io = 1mA
4.95 5.00 5.05 4.90 5.00 5.10 V
VREF Line Regulation
12V Vi 25V
2 20
2 20 mV
VREF Load Regulation
1 Io 20mA
3 25
3 25 mV
VREF/T Temperature Stability
(Note 2)
0.2 0.2 mV/°C
Total Output Variation
Line, Load, Temperature
4.9
5.1 4.82
5.18 V
eN Output Noise Voltage
10Hz f 10KHz Tj = 25°C
(note 2)
50
50 µV
Long Term Stability
Tamb = 125°C, 1000Hrs
(note 2)
5 25
5 25 mV
ISC Output Short Circuit
-30 -100 -180 -30 -100 -180 mA
OSCILLATOR SECTION
fOSC Frequency
Tj = 25°C
49 52 55 49 52 55 KHz
TA = Tlow to Thigh
48 – 56 48 – 56 KHz
TJ = 25°C (RT = 6.2k, CT = 1nF) 225 250 275 225 250 275 KHz
fOSC/V Frequency Change with Volt. VCC = 12V to 25V
– 0.2 1 – 0.2 1 %
fOSC/T Frequency Change with Temp. TA = Tlow to Thigh
– 1 – – 0.5 – %
VOSC
Idischg
Oscillator Voltage Swing (peak to peak)
Discharge Current (VOSC =2V) TJ = 25°C
TA = Tlow to Thigh
– 1.6 – – 1.6 – V
7.8 8.3 8.8 7.8 8.3 8.8 mA
7.5 – 8.8 7.6 – 8.8 mA
ERROR AMP SECTION
V2 Input Voltage
VPIN1 = 2.5V
2.45 2.50 2.55 2.42 2.50 2.58 V
Ib Input Bias Current
VFB = 5V
-0.1 -1
-0.1 -2 µA
AVOL
BW Unity Gain Bandwidth
2V Vo 4V
TJ = 25°C
65 90
0.7 1
65 90
0.7 1
dB
MHz
PSRR Power Supply Rejec. Ratio 12V Vi 25V
60 70
Io Output Sink Current
VPIN2 = 2.7V VPIN1 = 1.1V 2 12
60 70
2 12
dB
mA
Io Output Source Current
VPIN2 = 2.3V VPIN1 = 5V
-0.5 -1
-0.5 -1
mA
VOUT High
VOUT Low
CURRENT SENSE SECTION
VPIN2 = 2.3V;
RL = 15Kto Ground
VPIN2 = 2.7V;
RL = 15Kto Pin 8
5 6.2
5 6.2
V
0.8 1.1
0.8 1.1 V
GV Gain
(note 3 & 4)
2.85 3 3.15 2.85 3 3.15 V/V
V3 Maximum Input Signal
VPIN1 = 5V (note 3)
0.9 1 1.1 0.9 1 1.1 V
SVR
Ib
Supply Voltage Rejection
Input Bias Current
12 Vi 25V (note 3)
70
-2 -10
70 dB
-2 -10 µA
Delay to Output
150 300
150 300 ns
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UC3845B 電子部品, 半導体
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UC2842B/3B/4B/5B - UC3842B/3B/4B/5B
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 VO=2V to 4V 30
Gain
RL=100K
TA=25°C
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 20 40 60 80
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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)

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共有リンク

Link :


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