UC3844 UC3845 SO-14 UCX844 UCX845 UC2844 UC3844D UC3845D UC3844N UC3845N - Datasheet Archive

 

Advance Information High Performance Current Mode Controllers The UC3844, UC3845 series are high performance fixed frequency

 

(fc) MOTOROLA Advance Information High Performance Current Mode Controllers The UC3844 UC3844, UC3845 UC3845 series are high performance fixed frequency current mode controllers. They are specifically designed for Off-Line and do-to-dc converter applications offering the designer a cost effective 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, cycle-by-cycle current limiting, a latch for single pulse metering, and a flip-flop which blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed for 50% to 70%. These devices are available in an 8-pin dual-in-line plastic package as well as the 14-pin plastic surface mount (SO-14 SO-14). The SO-14 SO-14 package has separate power and ground pins for the totem pole output stage. The UCX844 UCX844 has UVLO thresholds of 16 V (on) and 10 V (off), ideally suited for off-line converters. The UCX845 UCX845 is tailored for lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off). • Current Mode Operation to 500 kHz Output Switching Frequency • Output Deadtime Adjustable from 50% to 70% • Automatic Feed Forward Compensation • Latching PWM for Cycle-By-Cycle Current Limiting • Internally Trimmed Reference with Undervoltage Lockout • High Current Totem Pole Output • Input Undervoltage Lockout with Hysteresis • Low Startup and Operating Current • Direct Interface with Motorola SENSEFET Products Simplified Block Diagram Pin numbers in parenthesis are for the D sulfa SO-14 SO-14 package. 1 UC3844 UC3844, 45 UC2844 UC2844, 45 HIGH PERFORMANCE CURRENT MODE CONTROLLERS n suffix füSfe PLASTIC PACKAGE CASE 626 B jl> d suffix ^Êk PLASTIC PACKAGE CASE 751A (SO-14 SO-14) 1 PIN CONNECTIONS Compensation T]vre, Voilage Feedback Z]vcc Current Sense 6 I Output RT'CTE Gnd (Top View) Compensation r NC ti li] NC Voltage Feedback jUvcc NC 13 Vo Current Sense 5 10] Output NC 6 j] Gnd Rr/c-r LL 8 | Power Ground (Top View) ORDERING INFORMATION Device Operating Temperature Flange Package UC3844D UC3844D TA '= 0" to +70°C SO-14 SO-14 UC3845D UC3845D SO-14 SO-14 UC3844N UC3844N Plastic UC3845N UC3845N Plastic UC2844D UC2844D Ta = - 25° to +85°C SO-14 SO-14 UC2845D UC2845D SO-14 SO-14 UC2844N UC2844N Plastic UC2845N UC2845N Plastic MOTOROLA ANALOG IC DEVICE DATA 3-573 UC3844 UC3844, 45 UC2844 UC2844, 45 MAXIMUM RATINGS Rating Symbol Value Unit Total Power Supply and Zener Current (Icc + lz) 30 mA Output Current, Source or Sink (Note 1) lo 1.0 A Output Energy (Capacltive Load per Cycle) w 5.0 nJ Current Sense and Voltage Feedback Inputs Vin - 0.3 to + 5.5 V Error Amp Output Sink Current _ ' io 10 mA Power Dissipation and Thermal Characteristics D Suffix, Plastic Package, Case 751A Maximum Power Dissipation @ Ta = 25°C Thermal Resistance Junction-to-Air N Suffix, Plastic Package, Case 626 Maximum Power Dissipation @ Ta = 25°C Thermal Resistance Junctlon-to-Air PD ReJA PD R6JA 862 145 1.25 100 mW »C/W W "C/W Operating Junction Temperature Tj + 150 °C Operating Ambient Temperature UC3844 UC3844, UC3845 UC3845 UC2844 UC2844, UC2845 UC2845 Ta 0 to + 70 - 25 to + 85 °c Storage Temperature Range Tstg - 65 to + 150 °c ELECTRICAL CHARACTERISTICS (Vcc = 15 V, [Note 2], Rj = 10 k, Cr = 3.3 riF, Ta = T|0W to Thigii [Note 3], unless otherwise noted.) UC284X UC284X UC384X UC384X Characteristics Symbol Min j Typ Max Min Typ Max Unit REFERENCE SECTION Reference Output Voltage (lo = 1 -0 mA, Tj = 25°C) Vref 4.95 5.0 5.05 4.9 5.0 5.1 V Line Regulation (Vcc = 12 V to 25 V) Regiine - 2.0 20 - 2.0 20 mV Load Regulation (lo = 1.0 mA to 20 mA) Regioad - 3.0 25 - 3.0 25 mV Temperature Stability Ts - 0.2 - - 0.2 - mV/°C Total Output Variation over Line, Load, Temperature Vref 4.9 - 5.1 4.82 5.18 V Output Noise Voltage (f = 10 Hz to kHz, Tj = 25°C) Vn - 50 - - 50 - HV Long Term Stability (Ta = 125°C for 1000 Hours) S - 5.0 - - â-  5.0 - mV Output Short Circuit Current isc -30 -85 -180 -30 -85 -180 mA OSCILLATOR SECTION Frequency Tj = 25°C -TA = Tlow to Thigh 'ose 47 46 52 57 60 47 46 52 57 60 kHz Frequency Change with Voltage (Vcc = 12 V to 25 V) Af0sc/AV - 0.2 1.0 - 0.2 1.0 % Frequency Change with Temperature Ta = T|0W to Thigh A'osc/AT - 5.0 - - 5.0 - % Oscillator Voltage Swing (Peak-to-Peak) Vose - 1.6 - - 1.6 - V Discharge Current (V0SG = 2.0 V, Tj = 25°C) •dischg - 10.8 - - 10.8 - mA NOTES: 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 ¡unction temperature as close to ambient as possible T|0W = 0°C for UC3844 UC3844, UC3845 UC3845 TMgh = +70°C for UC3844 UC3844, UC3845 UC3845 -25°C for UC2844 UC2844, UC2845 UC2845 +85°C for UC2844 UC2844, UC2845 UC2845 3-574 MOTOROLA ANALOG IC DEVICE DATA UC3844 UC3844, 45 UC2844 UC2844, 45 ELECTRICAL CHARACTERISTICS (Vcc = 15 V, [Note 2], Rj = 10 k, Cj = 3.3 nF, "Ia = T|0W to Thigh [Note 3], unless otherwise noted,) ' - . . UC284X UC284X UC384X UC384X f Characteristics Symbol Min Typ Max Min Typ Max Unit ERROR AMPLIFIER SECTION Voltage Feedback Input (Vo = 2.5 V) vfb 2.45 2.5 2.55 2,42 2.5 2.58 V Input Bias Current (Vfb = 2.7 V) l|B - -0.1 -1.0 - -0.1 -2.0 [1a Open Loop Voltage Gain (Vo = 2.0 V to 4.0 V) AvOL 65 90 - 65 90 - dB Unity Gain Bandwidth (tj = 25°C) bw 0.7 1.0 - 0.7 1.0 MHz Power Supply Rejection Ratio (Vcc = 12 V to 25 V) PSRR 60 70 - 60 70 - dB Output Current Sink (V0 = 1.1 V, VFB = 2.7 V) Source (Vo = 5.0 V, VpB = 2.3 V) 'Sink 'Source 2.0 -0.5 12 -1.0 - - 2.0 -0.5 12 -1.0 - mA Output Voltage Swing High State (R|_ = 15 k to ground, Vpe = 2.3 V) Low State (Rl = 15 k to Vref, Vpe = 2.7 V) VOH Vol 5.0 6.2 0.8 1.1 5.0 6.2 0.8 1.1 V CURRENT SENSE SECTION Current Sense Input Voltage Gain (Notes 4 & 5) Av 2.85 3.0 3.15 2.85 3.0 3.15 V/V Maximum Current Sense Input Threshold (Note 4) Vth 0.9 1.0 1.1 0.9 1.0 1.1 V Power Supply Rejection Ratio Vcc = 12 V to 25 V (Note 4) PSRR _ 70 _ _ 70 _ dB Input Bias Cuitent . IIB - -2.0 -10 - -2.0 -10 MA Propagation Delay (Current Sense Input to Output) tpLH(IN/OUT) - 150 300 . - 150 300 ns OUTPUT SECTION Output Voltage V Low State (Isink = 20 mA) vol - 0.1 0.4 - 0.1 0,4 ("Sink = 200 mA) - 1.6 2.2 - 1.6 2.2 High State (Isink = 20 mA) voh 12 13.5 - - 13 13.5 - ('Sink = 200 mA) 12 13.4 - 12 13.4 - Output Voltage with UVLO Activated vol(uvlo) V VCC = 6.0 v, 'Sink = 10 mA . - 0.1 1.1 - 0.1 1.1 Output Voltage Rise Time (C|_ = 1.0 nF, Tj = 25®C) tr - 50 150 - 50 150 ns Output Voltage Fall Time (C[_ = 1.0 nF, Tj = 25°C) tf ~ - 50 150 - 50 150 ns UNDERVOLTAGE LOCKOUT SECTION Startup Threshold Vth V UCX844 UCX844 15 16 17 14.5 16 17.5 UCX845 UCX845 7.8 8.4 9.0 7.8 8.4 9.0 Minimum Operating Voltage After Turn-On VcC(min) V UCX844 UCX844 9.0 10 11 8.5 10 11.5 UCX845 UCX845 7.0 7.6 8.2 7.0 7.6 8.2 PWM SECTION Duty Cycle % Maximum DCmax 46 48 50 47 48 50 Minimum DCmin - - 0 - - 0 TOTAL DEVICE Power Supply Current (Note 2) 'CC mA Startup: (Vcc = 6-5 V for UCX845A UCX845A, - 0.5 1.0 - 0.5 1.0 14 V for UCX844 UCX844) Operating - 12 17 - 12 17 Power Supply Zener Voltage (Ice = 25 mA) vz 30 36 - 30 36 - V NOTES: 2. Adjust Vqq 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 Tiow - O'C for UC3844 UC3844, UC3845 UC3845 " Thigh = +70"C for UC3844 UC3844, UC3845 UC3845 -25°C for UC2844 UC2844, UC2845 UC2845 +85"C for UC2844 UC2844, UC2845 UC2845 4. This parameter is measured at the latch trip point with Vpg = 0 V. „ _ . . . . _ . . . . AV Output Compensation 5. Comparator gain is defined as: Av-'- ._ _ _ - - AV Current Sense Input 3-574 MOTOROLA ANALOG IC DEVICE DATA UC3844 UC3844, 45 UC2844 UC2844, 45 Figure 1. Timing Resistor versus Oscillator Frequency 20 k 50k 100k 200k 500k fose OSCILLATOR FREQUENCY (Hz) 1.0 M 75 UJ s. § 70 g g 65 § £ 60 UJ a ¡Ü Ë* 5? 55 50 Figure 2. Output Deadtlme versus Oscillator Frequency ! .On ^ 1 ! 2.0 nF i 1 i 5, >nF '- / / i ST = 1 JnF / 1 7ì r t / 1 100 aoipt 1 1 S 30 pF 10k 20k 50k 100k 200 k 500k fuse OSCILLATOR FREQUENCY (Hzj ' 1.0 m Figure 3. Error Amp Small Signal Transient Response 2.55 V 2.5 v 2.45 V Figure 4. Error Amp Large Signal Transient Response 3.0 V 2.5 V 2.0 V 0.5 ns/DIV 1.0 (is/DIV Figure 5. Error Amp Open Loop Gain and Phase versus Frequency 100 co 2. fj 60