UNITRODE UC2577-ADJ Technical data

UC2577T-ADJ

	UC2577-ADJ
Simple Step-Up Voltage Regulator
FEATURES	DESCRIPTION
∙ Requires Few External Components	The UC2577-ADJ device provides all the active functions neces-

	∙	NPN Output Switches 3.0A, 65V(max)	sary to implement step-up (boost), flyback, and forward converter
			switching regulators. Requiring only a few components, these sim-

∙Extended Input Voltage Range: 3.0V to 40V ple regulators efficiently provide up to 60V as a step-up regulator,

∙Current Mode Operation for Improved Transient Response, Line Regulation, and Current Limiting

∙Soft Start Function Provides Controlled Startup

∙52kHz Internal Oscillator

∙Output Switch Protected by Current Limit, Undervoltage Lockout and Thermal Shutdown

∙Improved Replacement for LM2577-ADJ Series

and even higher voltages as a flyback or forward converter regulator.

The UC2577-ADJ features a wide input voltage range of 3.0V to 40V and an adjustable output voltage. An on-chip 3.0A NPN switch is included with undervoltage lockout, thermal protection circuitry, and current limiting, as well as soft start mode operation to reduce current during startup. Other features include a 52kHz fixed frequency on-chip oscillator with no external components and current mode control for better line and load regulation.

A standard series of inductors and capacitors are available from several manufacturers optimized for use with these regulators and are listed in this data sheet.

TYPICAL APPLICATIONS

∙Simple Boost and Flyback Converters

∙SEPIC Topology Permits Input Voltage to be Higher or Lower than Output Voltage

∙Transformer Coupled Forward Regulators

∙Multiple Output Designs

BLOCK DIAGRAM

CONNECTION DIAGRAM

5-Pin TO-220 (Top View)

T Package

Also available in TO-263 Package (TD).

UDG-94034

3/97

UC2577-ADJ

ABSOLUTE MAXIMUM RATINGS (Note 1)

RECOMMENDED OPERATING RANGE

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45V Output Switch Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65V Output Switch Current (Note 2) . . . . . . . . . . . . . . . . . . . . . 6.0A Power Dissipation . . . . . . . . . . . . . . . . . . . . . . Internally Limited Storage Temperature Range . . . . . . . . . . . . . −65°C to +150°C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . . 260°C Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . 150°C Minimum ESD Rating (C = 100pF, R = 15kΩ) . . . . . . . . . . . 2kV

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . 3.0V ≤ VIN ≤ 40V Output Switch Voltage . . . . . . . . . . . . . . . 0V ≤ VSWITCH ≤ 60V Output Switch Current . . . . . . . . . . . . . . . . . . . . ISWITCH ≤ 3.0A Junction Temperature Range . . . . . . . . . . −40°C ≤ TJ ≤ +125°C

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = −40°C to +125°C, VIN = 5V, VFB = VREF, ISWITCH = 0, and TA =TJ.

PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNITS
System Parameters Circuit Figure 1 (Note 3)
Output Voltage	VIN = 5V to 10V, ILOAD = 100mA to 800mA	11.40	12.0	12.60	V
	TJ = 25°C	11.60		12.40	V
Line Regulation	VIN = 3.0V to 10V, ILOAD = 300mA		20	100	mV
	TJ = 25°C			50	mV
Load Regulation	VIN = 5V, ILOAD = 100mA to 800mA		20	100	mV
	TJ = 25°C			50	mV
Efficiency	VIN = 5V, ILOAD = 800mA		80		%
Device Parameters
Input Supply Current	VFB = 1.5V (Switch Off)		7.5	14	mA
	TJ = 25°C			10	mA
	ISWITCH = 2.0A, VCOMP = 2.0V (Max Duty Cycle)		45	85	mA
	TJ = 25°C			70	mA
Input Supply UVLO	ISWITCH = 100mA		2.70	2.95	V
	TJ = 25°C			2.85	V
Oscillator Frequency	Measured at SWITCH Pin, ISWITCH = 100mA	42	52	62	kHz
	TJ = 25°C	48		56	kHz
Reference Voltage	Measured at FB Pin, VIN = 3.0V to 40V, VCOMP = 1.0V	1.206	1.230	1.254	V
	TJ = 25°C	1.214		1.246	V
Reference Voltage Line Regulation	VIN = 3.0V to 40V		0.5		mV
Error Amp Input Bias Current	VCOMP = 1.0V		100	800	nA
	TJ = 25°C			300	nA
Error Amp Transconductance	ICOMP = −30μA to +30μA, VCOMP = 1.0V	1600	3700	5800	μmho
	TJ = 25°C	2400		4800	μmho
Error Amp Voltage Gain	VCOMP = 0.8V to 1.6V, RCOMP = 1.0MW (Note 4)	250	800		V/V
	TJ = 25°C	500			V/V
Error Amplifier Output Swing	Upper Limit VFB = 1.0V	2.0	2.4		V
	TJ = 25°C	2.2			V
	Lower Limit VFB = 1.5V		0.3	0.55	V
	TJ = 25°C			0.40	V
Error Amp Output Current	VFB = 1.0V to 1.5V, VCOMP = 1.0V	±90	±200	±400	μA
	TJ = 25°C	±130		±300	μA
Soft Start Current	VFB = 1.0V, VCOMP = 0.5V	1.5	5.0	9.5	μA
	TJ = 25°C	2.5		7.5	μA
Maximum Duty Cycle	VCOMP = 1.5V, ISWITCH = 100mA	90	95		%
	TJ = 25°C	93			%

2

UC2577-ADJ

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = -40°C to +125°C, VIN = 5V, VFB = VREF, ISWITCH = 0, and TA =TJ.

PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNITS
Device Parameters (cont.)
Switch Transconductance			12.5		A/V
Switch Leakage Current	VSWITCH = 65V, VFB = 1.5V (Switch Off)		10	600	mA
	TJ = 25°C			300	mA
Switch Saturation Voltage	ISWITCH = 2.0A, VCOMP = 2.0V (Max Duty Cycle)		0.5	0.9	V
	TJ = 25°C			0.7	V
NPN Switch Current Limit	VCOMP = 2.0V	3.0	4.3	6.0	A
Thermal Resistance	Junction to Ambient		65		°C/W
	Junction to Case		2		°C/W
COMP Pin Current	VCOMP = 0		25	50	mA
	TJ = 25°C			40	mA

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating ratings

indicate conditions during which the device is intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics.

Note 2: Output current cannot be internally limited when the UC2577 is used as a step-up regulator. To prevent damage to

the switch, its current must be externally limited to 6.0A. However, output current is internally limited when the UC2577 is used as a flyback or forward converter regulator.

Note 3. External components such as the diode, inductor, input and output capacitors can affect switching regulator performance. When the UC2577 is used as shown in the Test Circuit, system performance will be as specified by the system parameters.

Note 4: A 1.0MW resistor is connected to the compensation pin (which is the error amplifier’s output) to ensure accuracy in measuring AVOL. In actual applications, this pin’s load resistance should be ³ 10MW, resulting in AVOL that is typically twice the guaranteed minimum limit.

			UDG-94035
L = 415-0930 (AIE)	COUT = Sprague Type 673D	R1	= 48.7k in series with 511W (1%)
D = any manufacturer	Electrolytic 680mF, 20V	R2	= 5.62k (1%)

Figure 1. Circuit Used to Specify System Parameters

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