UC3842G中文资料

UNISONIC TECHNOLOGIES CO., LTD

UC3842G

LINEAR INTEGRATED CIRCUIT

HIGH PERFORMANCE

CURRENT MODE CONTROLLER

■ DESCRIPTION

The UTC UC3842G of high performance current mode controller is specifically designed for off-line and DC-to-DC converter applications offering the designer a cost effective solution with minimal external components. This integrated circuit features approximately 300μA start up current, a precision reference trimmed the error amplifier input. Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, and so on.

■ FEATURES

* Low startup and operating current

* User defined switching frequency(Norm is 52kHz) * Power-saving mode for low power * Under voltage lockout with hysteresis * Over voltage protection

* Latching PWM for Cycle-By-Cycle current limiting

* Internally trimmed reference with undervoltage lockout

*Pb-free plating product number:

UC3842GL

ORDERING INFORMATION

Ordering Number

Normal Lead Free Plating

Package Packing

UC3842G-D08-T UC3842GL-D08-T DIP-8 Tube UC3842G-S08-R UC3842GL-S08-R SOP-8 Tape Reel UC3842G-S08-T UC3842GL-S08-T SOP-8 Tube

PIN CONFIGURATION

GND

OUT

V CC

V REF

CT CS FB COMP

■ PIN DESCRIPTION

PIN NO. PIN NAME I/O Function

1 COMP O This pin is error amplifier output

2 FB I The error amplifier inverting input

3 CS I Current sense input

4 CT I The capacitor controlling switch frequency

5 GND Ground

6 OUT O Output to the gate of external power MOS

7 V CC Supply voltage

8 V REF O Inter 5V reference voltage output

■ BLOCK DIAGRAM

ABSOLUTE MAXIMUM RATINGS (Ta ＝25°C)

PARAMETER SYMBOL RATINGS UNIT

Supply Voltage (Low Impedance Source) V CC 30 V

Supply Voltage (I CC <30mA) V CC Self Limiting V Output Current (Peak) I O(PEAK)±1 A Output Energy (Capacity load) 5 μJ

Junction Temperature T J +150 °C Operating Temperature T OPR -40 ~ +125 °C

Storage Temperature T STG -65 ~ +150 °C

Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied.

ELECTRICAL CHARACTERISTICS

(0°C ≤Ta ≤70°C, V CC =15V, C T =3.3n , unless otherwise specified)

PARAMETER SYMBOL TEST CONDITION MIN TYP MAX UNIT

STANDBY SECTION

Reduce Frequency Point of Standby Mode V COMP Right load 2.2 V REFERENCE SECTION Reference Output Voltage V REF I OUT = 1.0mA 4.95 5.0 5.05V Line Regulation ?V REF 12V ≤V CC ≤25V 3 20mV Load Regulation ?V REF I OUT =1.0mA to 20mA 8 25mV Output Short Circuit Current I SC -30 -65 -180mA OSCILLATOR SECTION

Frequency f OSC1 Normal 49 52 55KHz Frequency f OSC2 No load or right load 14 KHz

Frequency Change ?f OSC /?V 12V ≤V CC ≤25V 0.2 1.0 V OSC(P-P) 1.6 V V OSCL 1.2 V Oscillator Voltage

V OSCH 2.8 V

ERROR AMPLIFIER SECTION

Input Voltage

V I(EA) V COMP = 2.5V 2.42 2.50 2.58V Input Bias Current I I(BIAS) V FB =

5V -0.3 -2 μA AVOL

2V ≤V OUT ≤4V 60 90 dB Unity Gain Bandwidth T J =25°C(Note1) 0.7 1 MHz PSRR

12V ≤V CC ≤25V 60 70 dB Output Sink Current I SINK V FB =2.7V, V COMP =

1.1V 2 4 mA Output Source Current I SOURCE V FB =

2.3V, V COMP =5V -0.5 -0.7 mA V OUT High V OH V FB =2.3V, R L =15K to GND 5.0 5.6 V V OUT Low

V OL V FB =2.7V, R L =15K to V REF 0.8 1.1V

CURRENT SENSE SECTION Gain

G V (Note2,3) 2.85 3 3.15V/V Maximum Input Signal V I(MAX) V COMP =

5V(Note2) 0.9 1 1.1V PSRR

12V ≤V CC ≤25V 70 dB Input Bias Current I BIAS -2 -10μA Delay to Output 150 300nS

ELECTRICAL CHARACTERISTICS (Cont.)

PARAMETER SYMBOL TEST

CONDITION

MIN

TYP

MAX UNIT OUTPUT SECTION

Output Voltage With UVLO Active V OL(UVLO)V CC=6V,I SINK

=1mA

0.8

1.1V

I SINK =20mA

0.1

0.4V

V OL

I SINK =200mA

1.6

2.2V

I SOURCE =20mA 13

14.5

V

Output Voltage

V OH

I SOURCE =200mA 12

14.6

V

t R C L =1.0nF(Note1)

100

150

Output Voltage Rise and Fall time

t F C L

=1.0nF(Note1)

100

150

nS

UNDER VOLTAGE LOCKOUT SECTION

Startup Threshold V TH(STAR-UP) 13.5

15

16.5V Min Operating Voltage V OPR(MIN)After Turn-ON 8.5 10 11.5V

PWM SECTION

Max Duty Cycle D MAX92 94 %

Minimum Duty Cycle D MIN0

% TOTAL DEVICE

Power Supply Zener Voltage V Z I CC

=25mA 30

39

V

Power Operating Supply Current I CC Note2 7 10mA Startup Current I START-UP V CC=14V,UVLO Active 150 300μA Note: 1.These parameters, although guaranteed, are not 100% tested in production.

2.Parameters measured at trip point of latch with V FB=0.

3.Gain defined as: A=ΔV COMP/ΔV CS; 0≤V CS≤0.8V

OPEN-LOOP TEST CIRCUIT

C IN 470

μ

High peak current associated with capacity loads necessitate careful grounding techniques. Timing and bypass

capacitors should be connected close to pin5 in single point GND.

UNDER-VOLTAGE LOCKOUT

During Under-Voltage Lockout, the output driver is biased to a high impedance state. Pin6 should be shunt to GND with a bleeder resistor to prevent activing the power switch with output leakage currents.

ERROR AMPLIFIER CONFIGURATION

Error amplifier can source or sink up to 0.5mA

CURRENT SENSE CIRCUIT

Peak current (I S ) determined by the formula: I SMAX =1V/Rs. A small RC filter be required to suppress switch

transients

OSCILLATOR AND STANDBY MODE

We can judge the state of output load through the voltage of PIN1. In order to reduce the standby power, it will reduce the OSC frequency at right load. When V COMP ≤2.2V, the OSC frequency begins to reduce. The normal frequency is 52KHz, the minimum frequency is 14KHz.

2.2V 1.2V

OSC triangle wave

SHUTDOWN TECHNIQUE

Shutdown UTC UC3842G can be accomplished by two methods; either raise pin 3 above 1V or pull Pin 1 below a voltage two diode drops above ground.