Texas Instruments UC2577TDTR-ADJ, UC2577TD-ADJ, UC2577T-ADJ Datasheet

Simple Step-Up Voltage Regulator

•

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 impl ement 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

3/97

FEATURES DESCRIPTION

CONNECTION DIAGRAM

BLOCK DIAGRAM

UDG-94034

•

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

TYPICAL APPLICATIONS

5-Pin TO-220 (Top View)
T Package

Also available in TO-263 Package (TD).

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

System Parameters

Circuit Figure 1

(Note 3)

Output Voltage VIN = 5V to 10V, I

LOAD

= 100mA to 800mA 11.40 12.0 12.60 V

T

J

= 25°C 11.60 12.40 V

Line Regulation VIN = 3.0V to 10V, I

LOAD

= 300mA 20 100 mV

T

J

= 25°C50mV

Load Regulation VIN = 5V, I

LOAD

= 100mA to 800mA 20 100 mV

T

J

= 25°C50mV

Efficiency VIN = 5V, I

LOAD

= 800mA 80 %

Device Parameters

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

T

J

= 25°C10mA

I

SWITCH

= 2.0A, V

COMP

= 2.0V (Max Duty Cycle) 45 85 mA

T

J

= 25°C70mA

Input Supply UVLO I

SWITCH

= 100mA 2.70 2.95 V

T

J

= 25°C2.85V

Oscillator Frequency Measured at SWITCH Pin, I

SWITCH

= 100mA 42 52 62 kHz

T

J

= 25°C4856kHz

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

COMP

= 1.0V 1.206 1.230 1.254 V

T

J

= 25°C 1.214 1.246 V
Reference Voltage Line Regulation VIN = 3.0V to 40V 0.5 mV
Error Amp Input Bias Current V

COMP

= 1.0V 100 800 nA

T

J

= 25°C 300 nA

Error Amp Transconductance

I

COMP

= −30µA to +30µA, V

COMP

= 1.0V 1600 3700 5800

µ

mho

T

J

= 25°C 2400 4800

µmho

Error Amp Voltage Gain V

COMP

= 0.8V to 1.6V, R

COMP

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

T

J

= 25°C 500 V/V

Error Amplifier Output Swing Upper Limit V

FB

= 1.0V 2.0 2.4 V

T

J

= 25°C2.2V

Lower Limit V

FB

= 1.5V 0.3 0.55 V

T

J

= 25°C0.40V

Error Amp Output Current

V

FB

= 1.0V to 1.5V, V

COMP

= 1.0V

±

90±200±400 µA

T

J

= 25°C

±

130

±

300 µA

Soft Start Current

V

FB

= 1.0V, V

COMP

= 0.5V 1.5 5.0 9.5

µA

T

J

= 25°C2.57.5

µA

Maximum Dut y Cycle V

COMP

= 1.5V, I

SWITCH

= 100mA 90 95 %

T

J

= 25°C93%

Unless otherwise stated, these specifications apply for T

A

= −40°C to +125°C, VIN =

5V, VFB = V

REF

, I

SWITCH

= 0, and TA =TJ.

ELECTRICAL CHARACTERISTICS

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

ABSOLUTE MAXIMUM RATINGS

(Note 1)

UC2577-ADJ

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

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

SWITCH

≤ 60V

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

SWITCH

≤ 3.0A

Junction Te mperature Range . . . . . . . . . . −40°C ≤ TJ ≤ +125°C

2

UC2577-ADJ

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Device Parameters (cont.)

Switch Transconductance 12.5 A/V
Switch Leakage Current

V

SWITCH

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

µA

T

J

= 25°C300

µA

Switch Saturation Voltage I

SWITCH

= 2.0A, V

COMP

= 2.0V (Max Duty Cycle) 0.5 0.9 V

T

J

= 25°C0.7V

NPN Switch Current Limit V

COMP

= 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

V

COMP

= 0 25 50

µ

A

TJ = 25°C40

µA

Unless otherwise stated, these specifications apply for T

A

= −40°C to +125°C, VIN =

5V, VFB = V

REF

, I

SWITCH

= 0, and TA =TJ.

ELECTRICAL CHARACTERISTICS

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

indicate cond it io ns duri ng which the device is intended to be functional, but device pa ram et er sp ec ifications may not be
guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics.

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

the switch, its current must be externally limit ed 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. Wh en the UC2 57 7 is use d as sho w n in the Test Circuit, sys te m pe rfo r ma nc e wil l be as specified by the
system parameters.

Note 4: A 1.0M

Ω

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

measuring A

VOL.

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

VOL

that is typically twice

the guaranteed mi nimum limit.

Figure 1. Circuit Used to Specify System Parameters

UDG-94035

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

C

OUT

= Sprague Type 673D

Electrolytic 680µF, 20V

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

3