UNITRODE UC2577-ADJ Technical data

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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