HIGH PERFORMANCE CURRENT MODE CONTROLLERS

Description

Niveau: Supérieur, Doctorat, Bac+8
Device Operating Temperature Range Package HIGH PERFORMANCE CURRENT MODE CONTROLLERS ORDERING INFORMATION UC3844D UC3845D TA = 0° to +70°C TA = – 25° to +85°C SO–14 SO–14 PIN CONNECTIONS Order this document by UC3844/D D SUFFIX PLASTIC PACKAGE CASE 751A (SO–14) N SUFFIX PLASTIC PACKAGE CASE 626 1 8 1 14 (Top View) Vref (Top View) Compensation Voltage Feedback Current Sense RT/CT Vref VCC Output Gnd 1 2 3 4 5 6 7 8 Compensation NC Voltage Feedback NC Current Sense NC RT/CT NC VCC VC Output Gnd Power Ground 1 2 3 4 5 6 7 9 8 10 11 12 13 14 UC3844N UC3845N Plastic Plastic UC2844D UC2845D SO–14 SO–14 UC2844N UC2845N Plastic Plastic 1MOTOROLA ANALOG IC DEVICE DATA The UC3844, UC3845 series are high performance fixed frequency current mode controllers. They are specifically designed for Off–Line and dc–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.

• input bias


• current sense


• maintain junction temperature


• pwm section


• operating ambient


• so–14 so–14


• output voltage


• undervoltage lockout


• reference short

Sujets

• Motorola
• Régulation

Informations

• Publié par: profil-zyak-2012
• Nombre de lectures: 21
• Langue: English

Extrait

Order this document by UC3844/D
HIGH PERFORMANCE
The UC3844, UC3845 series are high performance fixed frequency
CURRENT MODEcurrent mode controllers. They are specifically designed for Off–Line and
dc–to–dc converter applications offering the designer a cost effective CONTROLLERS
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.
N SUFFIX
Also included are protective features consisting of input and reference PLASTIC PACKAGE
undervoltage lockouts each with hysteresis, cycle–by–cycle current limiting, CASE 626
a latch for single pulse metering, and a flip–flop which blanks the output off 8
every other oscillator cycle, allowing output deadtimes to be programmed for
1
50% to 70%. D SUFFIX
These devices are available in an 8–pin dual–in–line plastic package as PLASTIC PACKAGE
14CASE 751Awell as the 14–pin plastic surface mount (SO–14). The SO–14 package has
(SO–14) 1separate power and ground pins for the totem pole output stage.
The UCX844 has UVLO thresholds of 16 V (on) and 10 V (off), ideally
suited for off–line converters. The UCX845 is tailored for lower voltage
applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).
PIN CONNECTIONS
• Current Mode Operation to 500 kHz Output Switching Frequency
Compensation 1 8 V• Output Deadtime Adjustable from 50% to 70% ref
• Automatic Feed Forward Compensation Voltage Feedback 2 7 VCC
• Latching PWM for Cycle–By–Cycle Current Limiting 3 6Current Sense Output
• Internally Trimmed Reference with Undervoltage Lockout 45R /C GndT T
• High Current Totem Pole Output
(Top View)• Input Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
1 14Compensation Vref• Direct Interface with Motorola SENSEFET Products
2 13NC NC
3 12Voltage Feedback VCC
4 11 VNC C
5 10Current Sense Output
6 9NC GndSimplified Block Diagram
R /C Power Ground7 8T TV 7(12)CC
(Top View)V VCCref 5.0V
Undervoltage8(14) Reference
Lockout ORDERING INFORMATIONR
V Operatingref VCR Undervoltage Device Temperature Range Package7(11)
Lockout
UC3844D SO–14R C OutputT T
Oscillator Flip 6(10)4(7) UC3845D SO–14Flop
T = 0° to +70°CA&Voltage PWR GND UC3844N Plastic
LatchingFeedback 5(8)+
PWM– UC3845N Plastic2(3) Current
Error Sense UC2844D SO–14Amplifier 3(5)
1(1)
UC2845D SO–14Output
T = – 25° to +85°CAComp. Gnd 5(9) UC2844N Plastic
Pin numbers in parenthesis are for the D suffix SO–14 package. UC2845N Plastic
 Motorola, Inc. 1996 Rev 1
1MOTOROLA ANALOG IC DEVICE DATA

UC3844, 45 UC2844, 45
MAXIMUM RATINGS
Rating Symbol Value Unit
Total Power Supply and Zener Current (I + I ) 30 mACC Z
Output Current, Source or Sink (Note 1) I 1.0 AO
Output Energy (Capacitive Load per Cycle) W 5.0 J
Current Sense and Voltage Feedback Inputs V – 0.3 to + 5.5 Vin
Error Amp Output Sink Current I 10 mAO
Power Dissipation and Thermal Characteristics
D Suffix, Plastic Package, Case 751A
Maximum Power Dissipation @ T = 25°C P 862 mWA D
Thermal Resistance Junction–to–Air R 145 °C/WJA
N Suffix, Plastic Package, Case 626 = 25°C P 1.25 WA D R 100 °C/WJA
Operating Junction Temperature T + 150 °CJ
Operating Ambient T T °CA
UC3844, UC3845 0 to + 70
UC2844, UC2845 – 25 to + 85
Storage Temperature Range T – 65 to + 150 °Cstg
ELECTRICAL CHARACTERISTICS (V = 15 V, [Note 2], R = 10 k, C = 3.3 nF, T = T to T [Note 3], CC T T A low high
unless otherwise noted.)
UC284X UC384X
Characteristics Symbol Min Typ Max Min Typ Max Unit
REFERENCE SECTION
Reference Output Voltage (I = 1.0 mA, T = 25°C) V 4.95 5.0 5.05 4.9 5.0 5.1 VO J ref
Line Regulation (V = 12 V to 25 V) Reg – 2.0 20 – 2.0 20 mVCC line
Load Regulation (I = 1.0 mA to 20 mA) Reg – 3.0 25 – 3.0 25 mVO load
Temperature Stability T – 0.2 – – 0.2 – mV/°CS
Total Output Variation over Line, Load, Temperature V 4.9 – 5.1 4.82 – 5.18 Vref
Output Noise Voltage (f = 10 Hz to kHz, T = 25°C) V – 50 – – 50 – VJ n
Long Term Stability (T = 125°C for 1000 Hours) S – 5.0 – – 5.0 – mVA
Output Short Circuit Current I – 30 – 85 – 180 – 30 – 85 – 180 mASC
OSCILLATOR SECTION
Frequency f kHzosc
T = 25°C 47 52 57 47 52 57J
T = T to T 46 – 60 46 – 60A low high
Frequency Change with Voltage (V = 12 V to 25 V) f – 0.2 1.0 – 0.2 1.0 %CC osc/ V
Frequency Change with Temperature f – 5.0 – – 5.0 – %osc/ T
T = T to TA low high
Oscillator Voltage Swing (Peak–to–Peak) V – 1.6 – – 1.6 – Vosc
Discharge Current (V = 2.0 V, T = 25°C) I – 10.8 – – 10.8 – mAosc J dischg
NOTES: 1. Maximum Package power dissipation limits must be observed.
2. Adjust V above the Startup threshold before setting to 15 V.CC
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible
T = –20°C for UC3844, UC3845 T = +70°C for UC3844, UC3845low high
T = –25°C for UC2844, UC2845 T = +85°C for UC2844, UC2845low high
2 MOTOROLA ANALOG IC DEVICE DATA
mDDmqDDqUC3844, 45 UC2844, 45
ELECTRICAL CHARACTERISTICS (V = 15 V, [Note 2], R = 10 k, C = 3.3 nF, T = T to T [Note 3], CC T T A low high
unless otherwise noted,)
UC284X UC384X
Characteristics Symbol Min Typ Max Min Typ Max Unit
ERROR AMPLIFIER SECTION
Voltage Feedback Input (V = 2.5 V) V 2.45 2.5 2.55 2.42 2.5 2.58 VO FB
Input Bias Current (V = 2.7 V) I – –0.1 –1.0 – –0.1 –2.0 AFB IB
Open Loop Voltage Gain (V = 2.0 V to 4.0 V) A 65 90 – 65 90 – dBO VOL
Unity Gain Bandwidth (T = 25°C) BW 0.7 1.0 – 0.7 1.0 – MHzJ
Power Supply Rejection Ratio (V = 12 V to 25 V) PSRR 60 70 – 60 70 – dBCC
Output Current mA
Sink (V = 1.1 V, V = 2.7 V) I 2.0 12 – 2.0 12 –O FB Sink
Source (V = 5.0 V, V = 2.3 V) I –0.5 –1.0 – –0.5 –1.0 –O FB Source
Output Voltage Swing V
High State (R = 15 k to ground, V = 2.3 V) V 5.0 6.2 – 5.0 6.2 –L FB OH
Low State (R = 15 k to V , V = 2.7 V) V – 0.8 1.1 – 0.8 1.1L ref FB OL
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 4 & 5) A 2.85 3.0 3.15 2.85 3.0 3.15 V/VV
Maximum Current Sense Input Threshold (Note 4) V 0.9 1.0 1.1 0.9 1.0 1.1 Vth
Power Supply Rejection Ratio PSRR dB
V = 12 V to 25 V (Note 4) – 70 – – 70 –CC
Input Bias Current I – –2.0 –10 – –2.0 –10 AIB
Propagation Delay (Current Sense Input to Output) t – 150 300 – 150 300 nsPLH(IN/OUT)
OUTPUT SECTION
Output Voltage V
Low State (I = 20 mA) V – 0.1 0.4 – 0.1 0.4Sink OL
(I = 200 mA) – 1.6 2.2 – 1.6 2.2Sink
High State (I = 20 mA) V 12 13.5 – 13 13.5 –Sink OH
(I = 200 mA) 12 13.4 – 12 13.4 –Sink
Output Voltage with UVLO Activated V VOL(UVLO)
V = 6.0 V, I = 1.0 mA – 0.1 1.1 – 0.1 1.1CC Sink
Output Voltage Rise Time (C = 1.0 nF, T = 25°C) t – 50 150 – 50 150 nsL J roltage Fall Time (C, T = 25°C) t – 50 150 – 50 150 nsL J f
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold V Vth
UCX844 15 16 17 14.5 16 17.5
UCX845 7.8 8.4 9.0 7.8 8.4 9.0
Minimum Operating Voltage After Turn–On V VCC(min)
UCX844 9.0 10 11 8.5 10 11.5
UCX845 7.0 7.6 8.2 7.0 7.6 8.2
PWM SECTION
Duty Cycle %
Maximum DC 46 48 50 47 48 50max
Minimum DC – – 0 – – 0min
TOTAL DEVICE
Power Supply Current (Note 2) I mACC
Startup:
(V = 6.5 V for UCX845A, – 0.5 1.0 – 0.5 1.0CC
(V 14 V for UCX844) Operating – 12 17 – 12 17CC
Power Supply Zener Voltage (I = 25 mA) V 30 36 – 30 36 – VCC Z
NOTES: 2. Adjust V above the Startup threshold before setting to 15 V.CC
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible
T = –20°C for UC3844, UC3845 T = +70°C for UC3844, UC3845low high
T = –25°C for UC2844, UC2845 T = +85°C for UC2844, UC2845low high
4. This parameter is measured at the latch trip point with V = 0 V.FB
V Output Compensation
5. Comparator gain is defined as: AV
V Current Sense Input
3MOTOROLA ANALOG IC DEVICE DATA
DmDmUC3844, 45 UC2844, 45
Figure 1. Timing Resistor versus Figure 2. Output Deadtime versus
Oscillator Frequency Oscillator Frequency
100 75
V = 15 VCC
T = 25°CA 1.0 nF50
70
2.0 nF
20
5.0 nF
65
C = 10 nFT
10
605.0
2.0 55 100 pFNOTE: Output switches
at one–half the oscillator
200 pFfrequency. 500 pF
1.0 50
10 k 20 k 50