IC Phoenix
 
Home ›  UU5 > UC2842AD-UC2844AD-UC2845AN-UC3844AD-UC3844AN-UC3845AD,Current Mode PWMs
UC2842AD-UC2844AD-UC2845AN-UC3844AD-UC3844AN Fast Delivery,Good Price
Part Number:
If you need More Quantity or Better Price,Welcom Any inquiry.
We available via phone +865332716050 Email
Partno Mfg Dc Qty AvailableDescript
UC2842ADLMIN/a10avaiCurrent Mode PWMs
UC2845ANSTN/a1avaiHIGH PERFORMANCE CURRENT MODE PWM CONTROLLER
UC3844ADSTN/a17avaiCurrent Mode PWMs
UC3844ANUNITRODEN/a1000avaiHIGH PERFORMANCE CURRENT MODE PWM CONTROLLER
UC3845ADMSCN/a29avaiCurrent Mode PWMs
UC2844ADMSCN/a345avaiCurrent Mode PWMs
UC2844ADSTN/a3505avaiCurrent Mode PWMs


UC2844AD ,Current Mode PWMsfeatures: startup current• Automatic Feedforward Compensationis less than 0.5 mA, oscillator discha ..
UC2844AD ,Current Mode PWMsUC2842A/3A/4A/5AUC3842A/3A/4A/5A® HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER.TRIMMED OSCILLATOR D ..
UC2844AD ,Current Mode PWMs SLUS224F–SEPTEMBER 1994–REVISED OCTOBER 20174 Revision HistoryNOTE: Page numbers for previous revi ..
UC2844AD ,Current Mode PWMsElectrical Characteristics....... 711.4 Receiving Notification of Documentation Updates 256.6 Typic ..
UC2844AD ,Current Mode PWMsELECTRICAL CHARACTERISTICS ( [note 1] Unless otherwise stated, these specifications apply for-25 < ..
UC2844AD ,Current Mode PWMsfeatures: startup current• Automatic Feedforward Compensationis less than 0.5 mA, oscillator discha ..
UM61512AK-20 , 64K X 8 BIT HIGH SPEED CMOS SRAM
UM61512AS-15 , 64K X 8 BIT HIGH SPEED CMOS SRAM
UM621024CV-70L , 128K x 16 CMOS SRAM
UM621024CV-70LL , 128K x 16 CMOS SRAM
UM6264-10 , 8K x 8 CMOS SRAM
UM6264-10L , 8K x 8 CMOS SRAM


UC2842AD-UC2844AD-UC2845AN-UC3844AD-UC3844AN-UC3845AD
SMPS Controller
UC2842A/3A/4A /5A
UC3842A/3A/4A /5A

March 1999
HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER TRIMMED OSCILLATOR DISCHARGE CUR-
RENT. 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 CURRENT (< 0.5mA). DOUBLE PULSE SUPPRESSION
DESCRIPTION

The UC384xA family of control ICs provides the nec-
essary features to implement off-line or DC to DC
fixed frequency current mode control schemes with 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
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 UC3842A and UC3844A have
UVLO thresholds of 16V (on) and 10V (off), ideally
suited off-line applications The corresponding thresh-
olds for the UC3843A and UC3845A are 8.5 V and
7.9V. The UC3842A and UC3843A can operate to
duty cycles approaching 100%. A range of the zero to
< 50 % is obtained by the UC3844A and UC3845A 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 UC3844A and UC3845A)

1/15
All voltages are with respect to pin 5, all currents are positive into the specified terminal.PIN CONNECTION (top view)
ORDERING NUMBERS
ABSOLUTE MAXIMUM RATINGS
PIN FUNCTIONS
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

2/15
ELECTRICAL CHARACTERISTICS ( [note 1] Unless otherwise stated, these specifications apply for
-25 < Tamb < 85°C for UC284XA; 0 < Tamb < 70°C for UC384XA; Vi = 15V (note 5); RT = 10K; CT = 3.3nF)
THERMAL DATA
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

3/15
Notes :1. Max package power dissipation limits must be respected; low duty cycle pulse techniques are used during test maintain Tj as
close to Tamb as possible. These parameters, although guaranteed, are not 100% tested in production. Parameter measured at trip point of latch with VPIN2 = 0. Gain defined as :
Δ VPIN1A = ; 0 ≤ VPIN3 ≤ 0.8 VΔ VPIN3 Adjust Vi above the start threshold before setting at 15 V.
ELECTRICAL CHARACTERISTICS (continued)
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

4/15
Figure 1: Open Loop Test Circuit.
High peak currents associated with capacitive loads
necessitate careful grounding techniques. Timing
and bypass capacitors should be connected close
to pin 5 in a single point ground. The transistor and
5 KΩ potentiometer are used to sample the oscillator
waveform and apply an adjustable ramp to pin 3.
300 1K 3K 10K 30K RT(Ω)
10K
100K
(Hz)
Figure 2: Oscillator Frequency vs Timing Resis-

300 1K 3K 10K 30K RT(Ω)
D96IN363
Figure 3: Maximum Duty Cycle vs Timing Resis-
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

5/15
-55 -250 25 50 75 100 TA(˚C)
Idischg
(mA)
D95IN335
Figure 4: Oscillator Discharge Current vs. Tem-

perature. 100 1K 10K 100K 1M f(Hz)
(dB)
D95IN337
Figure 5: Error Amp Open-Loop Gain and

Phase vs. Frequency.
0246 VO(V)0.0
Vth
(V)
D95IN338
Figure 6: Current Sense Input Threshold vs. Er-

ror Amp Output Voltage. 20406080 100 Iref(mA)
D95IN339
Figure 7: Reference Voltage Change vs.

Source Current.
-55 -250 25 50 75 100 TA(˚C)
D95IN340
ISC
(mA)
Figure 8: Reference Short Circuit Current vs.

Temperature.
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

6/15
200 400 600 IO(mA)Vsat
(V)
D95IN341
Figure 9: Output Saturation Voltage vs. Load

Current. 102030 Vi(V)0
(mA)
D95IN342
Figure 10: Supply Current vs. Supply Voltage.
Figure 11: Output Waveform. Figure 12: Output Cross Conduction
Figure 13: Oscillator and Output Waveforms.

50ns/DIV
100ns/DIV
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

7/15
Figure 14 : Error Amp Configuration.
Figure 15 : Under Voltage Lockout.
Figure 16 : Current Sense Circuit .

Peak current (is) is determined by the formula
1.0 VIS max ≈ RS
A small RC filter may be required to suppress switch transients.
UC2842A/3A/4A/5A - UC3842A/3A/4A/5A

8/15
ic,good price


TEL:86-533-2716050      FAX:86-533-2716790
   

©2020 IC PHOENIX CO.,LIMITED