UNITRODE UC2577-ADJ Technical data

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Simple Step-Up Voltage Regulator

FEATURES DESCRIPTION

•

Requires Few External Components

•

NPN Output Switches 3.0A, 65V(max)

•

Extended Input Voltage Range: 3.0V to 40V

•

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

The UC2577-ADJ device provides all the active functions neces­sary to implement step-up (boost), flyback, and forward converter
switching regulat ors. R equirin g only a few c omponen ts, these sim­ple regula tors efficiently provide up to 60V as a step-up regulator,
and even high er volta ges as a flyback or forwa rd 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 star t 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.

UC2577-ADJ

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).

3/97

UDG-94034

UC2577-ADJ

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45V

Output Switch Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65V

Output Switch Current (Note 2) . . . . . . . . . . . . . . . . . . . . . 6.0A

Power Dissipation. . . . . . . . . . . . . . . . . . . . . . Internally Limited

RECOMMENDED OPERATING RANGE

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . 3.0V ≤ VIN ≤ 40V

Output Switch Voltage . . . . . . . . . . . . . . . 0V ≤ V

Output Switch Current . . . . . . . . . . . . . . . . . . . . I

Junction Temperature Range. . . . . . . . . . −40°C ≤ TJ ≤ +125°C

SWITCH

SWITCH

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

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, these specifications apply for T
5V, VFB = V

REF

, I

SWITCH

= 0, and TA =TJ.

= −40°C to +125°C, VIN =

A

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

System Parameters

Output Voltage VIN = 5V to 10V, I

Line Regulation VIN = 3.0V to 10V, I

Load Regulation VIN = 5V, I

Efficiency VIN = 5V, I

Circuit Figure 1

(Note 3)

= 100mA to 800mA 11.40 12.0 12.60 V

LOAD

= 25°C 11.60 12.40 V

T

J

= 300mA 20 100 mV

LOAD

T

= 25°C50mV

J

= 100mA to 800mA 20 100 mV

LOAD

= 25°C50mV

T

J

= 800mA 80 %

LOAD

Device Parameters

Input Supply Current VFB = 1.5V (Switch Off) 7.5 14 mA

= 25°C10mA

T

J

= 2.0A, V

I

SWITCH

T

= 25°C70mA

J

Input Supply UVLO I

= 100mA 2.70 2.95 V

SWITCH

= 25°C2.85V

T

J

Oscillator Frequency Measured at SWITCH Pin, I

T

= 25°C4856kHz

J

Reference Voltage Measured at FB Pin, VIN = 3.0V to 40V, V

= 25°C 1.214 1.246 V

T

J

= 2.0V (Max Duty Cycle) 45 85 mA

COMP

= 100mA 42 52 62 kHz

SWITCH

= 1.0V 1.206 1.230 1.254 V

COMP

Reference Voltage Line Regulation VIN = 3.0V to 40V 0.5 mV
Error Amp Input Bias Current V

Error Amp Transconductance

Error Amp Voltage Gain V

Error Amplifier Output Swing Upper Limit V

Error Amp Output Current

Soft Start Current

Maximum Dut y C yc le V

= 1.0V 100 800 nA

COMP

= 25°C 300 nA

T

J

= −30µA to +30µA, V

I

COMP

T

= 25°C 2400 4800

J

= 0.8V to 1.6V, R

COMP

= 25°C 500 V/V

T

J

= 1.0V 2.0 2.4 V

FB

= 25°C2.2V

T

J

Lower Limit V

= 25°C0.40V

T

J

= 1.0V to 1.5V, V

V

FB

T

= 25°C

J

V

= 1.0V, V

FB

T

= 25°C2.57.5

J

= 1.5V, I

COMP

= 25°C93%

T

J

= 1.5V 0.3 0.55 V

FB

COMP

SWITCH

COMP

COMP

= 0.5V 1.5 5.0 9.5

= 100mA 90 95 %

= 1.0V 1600 3700 5800

COMP

= 1.0MW (Note 4) 250 800 V/V

±

= 1.0V

±

90

130

±

200±400 µA

±

300 µA

≤ 60V

≤ 3.0A

µ

mho

µmho

µA
µA

2

UC2577-ADJ

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, these specifications apply for T
5V, VFB = V

REF

, I

SWITCH

= 0, and TA =TJ.

= −40°C to +125°C, VIN =

A

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Device Parameters (cont.)

Switch Transconductance 12.5 A/V
Switch Leakage Current

Switch Saturation Voltage I

NPN Switch Current Limit V
Thermal Resistance

V
T

SWITCH

T

= 65V, VFB = 1.5V (Switch Off) 10 600

SWITCH

= 25°C300

J

= 2.0A, V

J

= 25°C0.7V

= 2.0V 3.0 4.3 6.0 A

COMP

= 2.0V (Max Duty Cycle) 0.5 0.9 V

COMP

Junction to Ambient 65
Junction to Case 2

COMP Pin Current

V

= 0 25 50

COMP

TJ = 25°C40

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

indicate cond it io ns during which the devi ce is in te nd ed to be functional, but device parameter sp ec if ic at ions 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 in ternally 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. Wh en the UC2 577 is used as shown in the Test Circuit, sys te m pe rfo rmance will be as specif ie d by t he
system parameters.

Ω

Note 4: A 1.0M

measuring A

resistor is connected to the compensation pin (which is the error amplifier’s output) to ensure accuracy in

In actual applications, this pin’s load resistance should be ≥ 10MΩ, resulting in A

VOL.

that is typically twice

VOL

the guaranteed minimum limit.

µA
µA

°C/W
°

C/W

µ

A

µA

L = 415-0930 (AIE)
D = any manufacturer

C

= Sprague Type 673D

OUT

Electrolytic 680µF, 20V

R1 = 48.7k in series with 511Ω (1%)
R2 = 5.62k (1%)

Figure 1. Circuit Used to Specify System Parameters

3

UDG-94035