Fontes

Disponível somente no TrabalhosFeitos
  • Páginas : 8 (1952 palavras )
  • Download(s) : 0
  • Publicado : 15 de junho de 2012
Ler documento completo
Amostra do texto
www.fairchildsemi.com

UC3842/UC3843/UC3844/UC3845
SMPS Controller
Features
• • • • Low Start up Current Maximum Duty Clamp UVLO With Hysteresis Operating Frequency up to 500KHz

Description
The UC3842/UC3843/UC3844/UC3845 are fixed frequencycurrent-mode PWM controller. They are specially designed for Off-Line and DC to DC converter applications with minimum external components. Theseintegrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and a high current totempole output for driving a Power MOSFET. The UC3842 and UC3844 have UVLO thresholds of 16V (on) and 10V (off). The UC3843 and UC3845 are 8.5V(on) and 7.9V (off). The UC3842 and UC3843 can operate within 100%duty cycle. The UC3844 and UC3845 can operate with 50% duty cycle.
8-DIP 8-SOP

1

1

14-SOP

1

Internal Block Diagram

* NORMALLY 8DIP/8SOP PIN NO. * ( ) IS 14SOP PINNO. * TOGGLE FLIP FLOP USED ONLY IN UC3844, UC3845

Rev. 1.0.1
©2002 Fairchild Semiconductor Corporation

UC3842/UC3843/UC3844/UC3845

Absolute Maximum Ratings
Parameter Supply Voltage Output Current AnalogInputs (Pin 2.3) Error Amp Output Sink Current Power Dissipation at TA≤25°C (8DIP) Power Dissipation at TA≤25°C (8SOP) Power Dissipation at TA≤25°C (14SOP) Storage Temperature Range Lead Temperature (Soldering, 10sec) Symbol VCC IO V(ANA) ISINK (E.A) PD(Note1,2) PD(Note1,2) PD(Note1,2) TSTG TLEAD Value 30 ±1 -0.3 to 6.3 10 1200 460 680 -65 ~ +150 +300 Unit V A V mA mW mW mW °C °C

Note: 1. BoardThickness 1.6mm, Board Dimension 76.2mm ×114.3mm, (Reference EIA / JSED51-3, 51-7) 2. Do not exceeed PD and SOA (Safe Operation Area)

Power Dissipation Curve
1200 8DIP 1100 POWER DISSIPATION (mW) 1000 900 800 700 600 500 400 300
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

14SOP

8SOP

AMBIENT TEMPERATURE (℃)

Thermal Data
Characteristic Thermal Resistance Junction-ambientSymbol Rthj-amb(MAX) 8-DIP 100 8-SOP 265 14-SOP 180 Unit °C/W

Pin Array
8DIP,8SOP 14SOP

COMP 1

8

VREF

COMP 1

14 VREF

VFB 2

7

VCC

N/C

2

13

N/C

CURRENT SENSE

3

6

OUTPUT

VFB 3

12

VCC

RT/ CT 4

5 GND

N/C 4

11 PWR VC

CURRENT SENSE

5

10 OUTPUT

N/C

6

9

GND

RT/C T 7

8

PWR GND

2 UC3842/UC3843/UC3844/UC3845

Electrical Characteristics
(VCC=15V, RT=10kΩ, CT=3.3nF, TA= 0°C to +70°C, unless otherwise specified) Parameter REFERENCE SECTION Reference Output Voltage Line Regulation Load Regulation Short Circuit Output Current OSCILLATOR SECTION Oscillation Frequency Frequency Change with Voltage Oscillator Amplitude ERROR AMPLIFIER SECTION Input Bias Current Input Voltage Open Loop Voltage GainPower Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage CURRENT SENSE SECTION Gain Maximum Input Signal Power Supply Rejection Ratio Input Bias Current OUTPUT SECTION Low Output Voltage High Output Voltage Rise Time Fall Time Start Threshold Min. Operating Voltage (After Turn On) VOL ISINK = 20mA ISINK = 200mA VOH tR tF ISOURCE = 20mA ISOURCE =200mA TJ = 25°C, CL= 1nF (Note 3) TJ = 25°C, CL= 1nF (Note 3) UC3842/UC3844 UC3843/UC3845 UC3842/UC3844 UC3843/UC3844 13 12 14.5 7.8 8.5 7.0 0.08 1.4 13.5 13.0 45 35 16.0 8.4 10.0 7.6 0.4 2.2 150 150 17.5 9.0 11.5 8.2 V V V V ns ns V V V V GV VI(MAX) PSRR IBIAS (Note 1 & 2) Vpin1 = 5V(Note 1) 12V ≤ VCC ≤ 25V (Note 1,3) 2.85 0.9 3 1 70 -3 3.15 1.1 -10 V/V V dB µA IBIAS VI(E>A) GVO PSRR ISINK ISOURCEVOH VOL Vpin1 = 2.5V 2V ≤ VO ≤ 4V (Note3) 12V ≤ VCC ≤ 25V (Note3) Vpin2 = 2.7V, Vpin1 = 1.1V Vpin2 = 2.3V, Vpin1 = 5V Vpin2 = 2.3V, RL = 15kΩ to GND Vpin2 = 2.7V, RL = 15kΩ to Pin 8 2.42 65 60 2 -0.6 5 -0.1 2.50 90 70 7 -1.0 6 0.8 -2 2.58 1.1 µA V dB dB mA mA V V f ∆f/∆VCC VOSC TJ = 25°C 12V ≤ VCC ≤ 25V 47 52 0.05 1.6 57 1 kHz % VP-P VREF ∆VREF ∆VREF ISC TJ = 25°C, IREF = 1mA 12V ≤ VCC ≤ 25V 1mA...
tracking img