Philips UC3842N, UC3842D Datasheet

Philips Semiconductors Linear Products	Product specification
Current-mode PWM controller	UC3842

DESCRIPTION

The UC3842 is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting.

Protection circuitry includes built-in undervoltage lock-out and current limiting. Other features include fully-latched operation, a 1% trimmed bandgap reference, and start-up current less than 1mA.

These devices feature a totem-pole output designed to source and sink high peak current from a capacitive load, such as the gate of a power MOSFET. Consistent with N-channel power devices, the output is low in the OFF-state.

FEATURES

•Low start-up current (≤1mA)

•Automatic feed-forward compensation

•Pulse-by-pulse current limiting

•Enhanced load response characteristics

•Undervoltage lock-out with hysteresis

•Double pulse suppression

•High current totem-pole output

•Internally-trimmed bandgap reference

•400kHz operation, guaranteed min

PIN CONFIGURATIONS

N Package

COMP
	1				8	VREF
VFB	2				7	VCC
ISENSE	3				6	OUTPUT
RT/CT	4				5	GROUND
		TOP VIEW
		D Package
COMP	1	14				VREF
NC	2	13				NC
VFB	3	12				VCC
NC	4	11				VC
ISENSE	5	10				OUTPUT
NC	6	9				GROUND
RT/CT	7	8				POWER GROUND

TOP VIEW

APPLICATIONS

•Off-line switched mode power supplies

•DC-to-DC converters UC3842

BLOCK DIAGRAM

						7(11)
VCC	(12)7
		34V	UVLO			8(14)	VREF
	(9)5		S/R	5V			5.0V
GND			6V	REF			50mA
		16V
		2.5V			INTERNAL
					BIAS
RT/CT	(7)4	OSC
						6(10)
							OUTPUT
		ERROR			S
		AMP	2R
	(3)2	+				PWM
VFB
		±	R		R	LATCH
COMP	(1)1			1V	CURRENT
					SENSE
					COMPARATOR
CURRENT	(5)3
SENSE
						5(8)

NOTE:

Pin numbers in parentheses refer to the D package.

August 31, 1994

1100

853-0614 13721

Philips Semiconductors Linear Products	Product specification
Current-mode PWM controller	UC3842

ORDERING INFORMATION

DESCRIPTION	TEMPERATURE RANGE	ORDER CODE	DWG #
8-Pin Plastic Dual In-Line Package (DIP)	0 to +70°C	UC3842N	0404B
14-Pin Plastic Small Outline (SO) Package	0 to +70°C	UC3842D	0405B

ABSOLUTE MAXIMUM RATINGS1

SYMBOL	PARAMETER	RATING	UNIT
VCC	Supply voltage (ICC<30mA)		Self-Limiting
VCC	Supply voltage	30	V
	(low impedance source)
I	Output current 2, 3	±1	A
OUT
	Output energy (capacitive load)	5	μJ
	Analog inputs (Pin 2, Pin 3)	-0.3 to 6.3	V
	Error amp output sink current	10	mA
PD	Power dissipation at TA≤70°C	1	W
	(derate 12.5mW/°C for T >70°C)2
	A
TSTG	Storage temperature range	-65 to +150	°C
TSOLD	Lead temperature	300	°C
	(soldering, 10sec max)

NOTES:

1.All voltages are with respect to Pin 5; all currents are positive into the specified terminal.

2.See section in application note on ªPower Dissipation Calculationº.

3.This parameter is guaranteed, but not 100% tested in production.

August 31, 1994

1101

Philips Semiconductors Linear Products	Product specification
Current-mode PWM controller	UC3842

DC AND AC ELECTRICAL CHARACTERISTICS

0≤TJ≤70°C for UC3842; VCC=15V; RT=10kW; CT=3.3nF, unless otherwise specified.

	SYMBOL	PARAMETER	TEST CONDITIONS		UC3842		UNIT
				Min	Typ	Max

Reference section

VOUT	Output voltage	TJ=25°C, IO=1mA			4.90	5.00	5.10	V
	Line regulation	12≤VIN≤25V				6	20	mV
	Load regulation	1≤IO≤20mA				6	25	mV
	Temp. stability1					0.2	0.4	mV/°C
	Total output variation1	Line, load, temp.			4.82		5.18	V
V	Output noise voltage1	10Hz≤f≤10kHz, T =25°C				50		μV
NOISE				J
	Long-term stability1	T =125°C, 1000 Hrs.				5	25	mV
		J
	Output short-circuit	TJ=25			-30	-100	-130	mA
	Output short-circuit	-55<TJ≤0°C			-30	-100	-180	mA
Oscillator section
	Initial accuracy	TJ=25°C			47	52	57	kHz
	Voltage stability	12≤VCC≤25V				0.2	1	%
	Temp. stability1	T	≤T ≤T			5		%
		MIN	J MAX
	Amplitude	VPIN 4 peak-to-peak				1.7		V
Error amp section
	Input voltage	V Pin 1=2.5V			2.42	2.50	2.58	V
IBIAS	Input bias current					-0.3	-2	μA
AVOL		2≤VO≤4V			65	90		dB
	Unity gain bandwidth1	T =25°C			0.7	1		MHz
		J
	Unity gain bandwidth	TMIN<TJ<TMAX			0.5			MHz
PSRR	Power supply rejection ratio	12≤VCC≤25V			60	70		dB
ISINK	Output sink current	VPIN 2=2.7V, VPIN 1=1.1V			2	6		mA
ISOURCE	Output source current	VPIN 2=2.3V, VPIN 1=5V			-0.5	-0.8		mA
	VOUT High	VPIN 2=2.3V, RL=15k to ground			5	6		V
	VOUT Low	VPIN 2=2.7V, RL=15k to Pin 8				0.7	1.1	V
Current sense section
	Gain 2, 3				2.85	3	3.15	V/V
	Maximum input signal2	V		=5V	0.9	1	1.1	V
		PIN 1
PSRR	Power supply rejection ratio2	12≤VCC≤25V				70		dB
IBIAS	Input bias current					-2	-10	μA
	Delay to output1					150	300	ns

August 31, 1994

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