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Part: UC2844BD1R2
Category:
Power Management
-> AC-DC Controllers/Converters
-> AC-DC Switching
-> Off-Line Controllers
Description: 1A, 52kHz (250kHz Max) Current Mode PWM Control Circuit With 16V Uvlo Threshold And 48% Max Duty Cycle, Package: Soic, Pins=8
Company: ON Semiconductor
Datasheet: Download UC2844BD1R2 datasheet File size : 216 kB
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Datasheet text preview:
UC3844B, UC3845B, UC2844B, UC2845B High Performance Current Mode Controllers
The UC3844B, UC3845B series are high performance fixed frequency current mode controllers. They are specifically designed for OffLine and dctodc converter applications offering the designer a costeffective solution with minimal external components. These integrated circuits feature an oscillator, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving a power MOSFET. Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cyclebycycle current limiting, a latch for single pulse metering, and a flipflop which blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed from 50% to 70%. These devices are available in an 8pin dualinline and surface mount (SO8) plastic package as well as the 14pin plastic surface mount (SO14). The SO14 package has separate power and ground pins for the totem pole output stage. The UCX844B has UVLO thresholds of 16 V (on) and 10 V (off), ideally suited for offline converters. The UCX845B is tailored for lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off). · Trimmed Oscillator for Precise Frequency Control · Oscillator Frequency Guaranteed at 250 kHz · Current Mode Operation to 500 kHz Output Switching Frequency · Output Deadtime Adjustable from 50% to 70% · Automatic Feed Forward Compensation · Latching PWM for CycleByCycle Current Limiting · Internally Trimmed Reference with Undervoltage Lockout · High Current Totem Pole Output · Undervoltage Lockout with Hysteresis · Low Startup and Operating Current
VCC 7(12)
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8 1
PDIP8 N SUFFIX CASE 626
8 1
SO8 D1 SUFFIX CASE 751
14 1
SO14 D SUFFIX CASE 751A
PIN CONNECTIONS
Compensation Voltage Feedback Current Sense RT/CT
1 2 3 4 8 7 6 5
Vref VCC Output Gnd
(Top View) Compensation NC Voltage Feedback NC Current Sense NC RT/CT
1 2 3 4 5 6 7 14 13 12 11 10 9 8
Vref 8(14) R R Vref Undervoltage Lockout
5.0V Reference
VCC Undervoltage Lockout VC 7(11) Output 6(10) Power Ground 5(8) Current Sense Input
Vref NC VCC VC Output Gnd Power Ground
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package dimensions section on page 16 of this data sheet.
RT/CT Voltage Feedback Input Output/ Compensation
4(7)
Oscillator
Latching PWM
DEVICE MARKING INFORMATION
See general marking information in the device marking section on page 17 of this data sheet.
2(3) 1(1)
Error Amplifier
3(5) Gnd 5(9)
Pin numbers in parenthesis are for the D suffix SO-14 package.
Figure 1. Simplified Block Diagram
© Semiconductor Components Industries, LLC, 2001
1
October, 2001 Rev. 2
Publication Order Number: UC3844B/D
UC3844B, UC3845B, UC2844B, UC2845B
MAXIMUM RATINGS
Rating Total Power Supply and Zener Current Output Current, Source or Sink (Note 1) Output Energy (Capacitive Load per Cycle) Current Sense and Voltage Feedback Inputs Error Amp Output Sink Current Power Dissipation and Thermal Characteristics D Suffix, Plastic Package, SO14 Case 751A Maximum Power Dissipation @ TA = 25°C Thermal Resistance, JunctiontoAir D1 Suffix, Plastic Package, SO8 Case 751 Maximum Power Dissipation @ TA = 25°C Thermal Resistance, JunctiontoAir N Suffix, Plastic Package, Case 626 Maximum Power Dissipation @ TA = 25°C Thermal Resistance, JunctiontoAir Operating Junction Temperature Operating Ambient Temperature UC3844B, UC3845B UC2844B, UC2845B Storage Temperature Range Symbol (ICC + IZ) IO W Vin IO Value 30 1.0 5.0 0.3 to + 5.5 10 Unit mA A µJ V mA
PD R J A PD R J A PD R J A TJ TA
862 145 702 178 1.25 100 +150 0 to + 70 25 to + 85
mW °C/W mW °C/W W °C/W °C °C
Tstg
65 to +150
°C
ELECTRICAL CHARACTERISTICS (VCC = 15 V [Note 2], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max values
TA is the operating ambient temperature range that applies [Note 3], unless otherwise noted.) UC284XB Characteristic REFERENCE SECTION Reference Output Voltage (IO = 1.0 mA, TJ = 25°C) Line Regulation (VCC = 12 V to 25 V) Load Regulation (IO = 1.0 mA to 20 mA) Temperature Stability Total Output Variation over Line, Load, and Temperature Output Noise Voltage (f = 10 Hz to 10 kHz, TJ = 25°C) Long Term Stability (TA = 125°C for 1000 Hours) Output Short Circuit Current OSCILLATOR SECTION Frequency TJ = 25°C TA = Tlow to Thigh TJ = 25°C (RT = 6.2 k, CT = 1.0 nF) Frequency Change with Voltage (VCC = 12 V to 25 V) Frequency Change with Temperature (TA = Tlow to Thigh) Oscillator Voltage Swing (PeaktoPeak) Discharge Current (VOSC = 2.0 V) TJ = 25°C TA = Tlow to Thigh (UC284XB, UC384XB) TA = Tlow to Thigh (UC384XBV) fOSC 49 48 225 fOSC/V fOSC/T VOSC Idischg 7.8 7.5 8.3 8.8 8.8 7.8 7.6 7.2 8.3 8.8 8.8 8.8 52 250 0.2 1.0 1.6 55 56 275 1.0 49 48 225 52 250 0.2 0.5 1.6 55 56 275 1.0 % % V mA kHz Vref Regline Regload TS Vref Vn S ISC 4.95 4.9 30 5.0 2.0 3.0 0.2 50 5.0 85 5.05 20 25 5.1 180 4.9 4.82 30 5.0 2.0 3.0 0.2 50 5.0 85 5.1 20 25 5.18 180 V mV mV mV/°C V µV mV mA Symbol Min Typ Max UC384XB, XBV Min Typ Max Unit
1. Maximum package power dissipation limits must be observed. 2. Adjust VCC above the Startup threshold before setting to 15 V. 3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. Tlow = 0°C for UC3844B, UC3845B Thigh = + 70°C for UC3844B, UC3845B = 25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B = 40°C for UC3844BV, UC3845BV = +105°C for UC3844BV, UC3845BV
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UC3844B, UC3845B, UC2844B, UC2845B
ELECTRICAL CHARACTERISTICS (VCC = 15 V [Note 4], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max values
TA is the operating ambient temperature range that applies [Note 5], unless otherwise noted.) UC284XB Characteristic ERROR AMPLIFIER SECTION Voltage Feedback Input (VO = 2.5 V) Input Bias Current (VFB = 5.0 V) Open Loop Voltage Gain (VO = 2.0 V to 4.0 V) Unity Gain Bandwidth (TJ = 25°C) Power Supply Rejection Ratio (VCC = 12 V to 25 V) Output Current Sink (VO = 1.1 V, VFB = 2.7 V) Source (VO = 5.0 V, VFB = 2.3 V) Output Voltage Swing High State (RL = 15 k to ground, VFB = 2.3 V) Low State (RL = 15 k to Vref, VFB = 2.7 V) (UC284XB, UC384XB) (UC384XBV) CURRENT SENSE SECTION Current Sense Input Voltage Gain (Notes 6 & 7) (UC284XB, UC384XB) (UC384XBV) Maximum Current Sense Input Threshold (Note 6) (UC284XB, UC384XB) (UC384XBV) Power Supply Rejection Ratio (VCC = 12 V to 25 V) (Note 6) Input Bias Current Propagation Delay (Current Sense Input to Output) OUTPUT SECTION Output Voltage Low State (ISink = 20 mA) (ISink = 200 mA, UC284XB, UC384XB) (ISink = 200 mA, UC384XBV) High State (ISource = 20 mA, UC284XB, UC384XB) (ISource = 20 mA, UC384XBV) (ISource = 200 mA) Output Voltage with UVLO Activated (VCC = 6.0 V, ISink = 1.0 mA) Output Voltage Rise Time (CL = 1.0 nF, TJ = 25°C) Output Voltage Fall Time (CL = 1.0 nF, TJ = 25°C) UNDERVOLTAGE LOCKOUT SECTION Startup Threshold UCX844B, BV UCX845B, BV Minimum Operating Voltage After TurnOn UCX844B, BV UCX845B, BV Vth 15 7.8 VCC(min) 9.0 7.0 10 7.6 11 8.2 8.5 7.0 10 7.6 11.5 8.2 16 8.4 17 9.0 14.5 7.8 16 8.4 17.5 9.0 V V V VOL 13 12 0.1 1.6 13.5 13.4 0.1 50 50 0.4 2.2 1.1 150 150 13 12.9 12 0.1 1.6 1.6 13.5 13.4 0.1 50 50 0.4 2.2 2.3 1.1 150 150 V ns ns AV 2.85 Vth 0.9 PSRR IIB tPLH(In/Out) 1.0 70 2.0 150 1.1 10 300 0.9 0.85 1.0 1.0 70 2.0 150 1.1 1.1 10 300 dB µA ns 3.0 3.15 2.85 2.85 3.0 3.0 3.15 3.25 V V/V VFB IIB AVOL BW PSRR ISink ISource VOH VOL 2.45 65 0.7 60 2.0 0.5 5.0 2.5 0.1 90 1.0 70 12 1.0 6.2 0.8 2.55 1.0 1.1 2.42 65 0.7 60 2.0 0.5 5.0 2.5 0.1 90 1.0 70 12 1.0 6.2 0.8 0.8 2.58 2.0 V 1.1 1.2 V µA dB MHz dB mA Symbol Min Typ Max UC384XB, XBV Min Typ Max Unit
VOH
VOL(UVLO) tr tf
4. Adjust VCC above the Startup threshold before setting to 15 V. 5. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. Thigh = + 70°C for UC3844B, UC3845B Tlow = 0°C for UC3844B, UC3845B = 25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B = 40°C for UC3844BV, UC3845BV = +105°C for UC3844BV, UC3845BV 6. This parameter is measured at the latch trip point with VFB = 0 V. 7. Comparator gain is defined as: AV = V Output/Compensation V Current Sense Input
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