Datasheet TL497AIN, TL497AIJ, TL497AID, TL497AIDR, TL497ACPWR Datasheet (Texas Instruments)

TL497A

SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

1

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

D

High Efficiency . . . 60% or Greater

D

Output Current . . . 500 mA

D

Input Current Limit Protection

D

TTL-Compatible Inhibit

D

Adjustable Output Voltage

D

Input Regulation . . . 0.2% Typ

D

Output Regulation . . . 0.4% Typ

D

Soft Start-Up Capability

description

The TL497A incorporates all the active functions
required in the construction of switching voltage
regulators. It can also be used as the control
element to drive external components for high-power-output applications. The TL497A was designed for ease
of use in step-up, step-down, or voltage-inversion applications requiring high efficiency.

The TL497A is a fixed-on-time variable-frequency switching-voltage-regulator control circuit. The switch-on
time is programmed by a single external capacitor connected between FREQ CONTROL and GND. This
capacitor, CT, is charged by an internal constant-current generator to a predetermined threshold. The charging
current and the threshold vary proportionally with V

CC

. Thus, the switch-on time remains constant over the

specified range of input voltage (4.5 V to 12 V). Typical on times for various values of CT are as follows:

TIMING CAPACITOR, CT (pF) 200 250 350 400 500 750 1000 1500 2000
ON TIME (µs) 19 22 26 32 44 56 80 120 180

The output voltage is controlled by an external resistor ladder network (R1 and R2 in Figures 1, 2, and 3) that
provides a feedback voltage to the comparator input. This feedback voltage is compared to the reference
voltage of 1.2 V (relative to SUBSTRA TE) by the high-gain comparator. When the output voltage decays below
the value required to maintain 1.2 V at the comparator input, the comparator enables the oscillator circuit, which
charges and discharges C

T

as described above. The internal pass transistor is driven on during the charging

of C

T

. The internal transistor can be used directly for switching currents up to 500 mA. Its collector and emitter
are uncommitted, and it is current driven to allow operation from the positive supply voltage or ground. An
internal Schottky diode matched to the current characteristics of the internal transistor also is available for
blocking or commutating purposes. The TL497A also has on-chip current-limit circuitry that senses the peak
currents in the switching regulator and protects the inductor against saturation and the pass transistor against
overstress. The current limit is adjustable and is programmed by a single sense resistor, R

CL

, connected
between VCC and CUR LIM SENS. The current-limit circuitry is activated when 0.7 V is developed across RCL.
External gating is provided by the INHIBIT input. When the INHIBIT input is high, the output is turned off.

Simplicity of design is a primary feature of the TL497A. With only six external components (three resistors, two
capacitors, and one inductor), the TL497A operates in numerous voltage-conversion applications (step-up,
step-down, invert) with as much as 85% of the source power delivered to the load. The TL497A replaces the
TL497 in all applications.

The TL497AC is characterized for operation from 0°C to 70°C. The TL497AI is characterized for operation from
–40°C to 85°C.

Copyright  1999, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

1
2
3
4
5
6
7

14
13
12
11
10

9
8

COMP INPUT

INHIBIT

FREQ CONTROL

SUBSTRATE

GND

CATHODE

ANODE

V

CC

CUR LIM SENS
BASE DRIVE

†

BASE

†

COL OUT
NC
EMIT OUT

(TOP VIEW)

D, N, OR PW PACKAGE

NC – No internal connection

†

BASE (11) and BASE DRIVE (12) are used for device testing
only. They normally are not used in circuit applications of the
device.

TL497A
SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

2

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

AVAILABLE OPTIONS

PACKAGED DEVICES

T

A

SMALL-OUTLINE

(D)

PLASTIC DIP

(N)

SHRINK

SMALL-OUTLINE

(PW)

CHIP

FORM

(Y)

0°C to 70°C TL497ACD TL497ACN TL497ACPW TL497AY

–40°C to 85°C TL497AID TL497AIN — —

The D and PW packages are only taped and reeled. Add the suffix R to the device type (e.g.,
TL497ACPWR). Chip forms are tested at 25°C.

functional block diagram

BASE

†

11
12

BASE DRIVE

†

CUR LIM SENS

FREQ CONTROL

INHIBIT

SUBSTRATE

COMP INPUT

CATHODE

Current

Limit

Sense

13

3
2

1

4

6

1.2-V

Reference

10

8

7

COL OUT

EMIT OUT

ANODE

Oscillator

†

BASE and BASE DRIVE are used for device testing only. They normally are not used in circuit applications of the device.

TL497A

SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

3

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)

†

Supply voltage, VCC (see Note 1) 15 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Output voltage, VO 35 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input voltage, VI(COMP INPUT) 5 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input voltage, V

I

(INHIBIT) 5 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Diode reverse voltage 35 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power switch current 750 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Diode forward current 750 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Package thermal impedance, θJA (see Notes 2 and 3): D package 86°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . .

N package 101°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . .

PW package 113°C/W. . . . . . . . . . . . . . . . . . . . . . . . . .

Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range, T

stg

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

†

Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and

functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTES: 1. All voltage values except diode voltages are with respect to network ground terminal.

2. Maximum power dissipation is a function of TJ(max),

θ

JA

, and TA. The maximum allowable power dissipation at any allowable

ambient temperature is PD = (TJ(max) – TA)/

θ

JA

. Operating at the absolute maximum TJ of 150°C can impact reliability.

3. The package thermal impedance is calculated in accordance with JESD 51, except for through-hole packages, which use a trace
length of zero.

recommended operating conditions

MIN MAX UNIT

Supply voltage, V

CC

4.5 12 V

High-level input voltage, V

IH

INHIBIT pin 2.5 V

Low-level input voltage, V

IL

INHIBIT pin 0.8 V
Step-up configuration (see Figure 1) VI + 2 30

Output voltage Step-down configuration (see Figure 2) V

refVI

– 1 V

Inverting regulator (see Figure 3) –V

ref

–25
Power switch current 500 mA
Diode forward current 500 mA

p

p

TL497AC 0 70

°

O erating free-air tem erature range, T

A

TL497AI –40 85

°C

TL497A
SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

4

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

electrical characteristics over recommended operating conditions, V

CC

= 6 V (unless otherwise

noted)

TL497AC TL497AI

PARAMETER

TEST CONDITIONS

T

A

†

MIN TYP‡MAX MIN TYP‡MAX

UNIT

High-level input current, INHIBIT V

I(I)

= 5 V Full range 0.8 1.5 0.8 1.5 mA

Low-level input current, INHIBIT V

I(I)

= 0 V Full range 5 10 5 20 µA
Comparator reference voltage VI = 4.5 V to 6 V Full range 1.08 1.2 1.32 1.14 1.2 1.26 V
Comparator input bias current VI = 6 V Full range 40 100 40 100 µA

IO = 100 mA 25°C 0.13 0.2 0.13 0.2

Switch on-state voltage

V

I

=

4.5 V

IO = 500 mA Full range 0.85 1

V

25°C 10 50 10 50

Switch off-state current

V

I

= 4.5 V,

V

O

= 30

V

Full range 200 500

µ

A

Sense voltage, CUR LIM SENS VI = 6 V 25°C 0.45 1 0.45 1 V

IO = 10 mA Full range 0.75 0.85 0.75 0.95

Diode forward voltage

IO = 100 mA Full range 0.9 1 0.9 1.1

V
IO = 500 mA Full range 1.33 1.55 1.33 1.75
IO = 500 µA Full range 30

Diode reverse voltage

IO = 200 µA Full range 30

V

pp

25°C 11 14 11 14

On-state supply current

Full range 15 16

mA

pp

25°C 6 9 6 9

Off-state supply current

Full range 10 11

mA

†

Full range is 0°C to 70°C for the TL497AC and –40°C to 85°C for the TL497AI.

‡

All typical values are at TA = 25°C.

electrical characteristics over recommended operating conditions, V

CC

= 6 V, T

A

= 25°C (unless

otherwise noted)

TL497AY

PARAMETER

TEST CONDITIONS

MIN TYP MAX

UNIT

High-level input current, INHIBIT V

I(I)

= 5 V 0.8 mA

Low-level input current, INHIBIT V

I(I)

= 0 V 5 µA
Comparator reference voltage VI = 4.5 V to 6 V 1.2 V
Comparator input bias current VI = 6 V 40 µA
Switch on-state voltage VI = 4.5 V, IO = 100 mA 0.13 V
Switch off-state current VI = 4.5 V, VO = 30 V 10 µA

IO = 10 mA 0.75

Diode forward voltage

IO = 100 mA 0.9

V

IO = 500 mA 1.33
On-state supply current 11 mA
Off-state supply current 6 mA

TL497A

SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

5

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

V

I

L

14 13 10 8

7654321

TL497A

R2 = 1.2 kΩ

R1

V

O

C

O

BASIC CONFIGURATION

(Peak Switching Current = I

(PK)

< 500 mA)

V

I

R

CL

L

R1

8

101314

12345

EXTENDED POWER CONFIGURATION

(using external transistor)

TL497A

DESIGN EQUATIONS

I

(PK)

+

2IOmax

ƪ

V

O

V

I

ƫ

L(mH)

+

V

I

I

(PK)

ton(ms)

CT(pF)[12 ton(ms)

R1+(VO–1.2V)k

W

Choose L (50 to 500 µH), calculate
ton (25 to 150 µs)

RCL+

0.5 V
I

(PK)

CO(mF)[ton(ms)

ƪ

V

I

V

O

I

(PK)

)

I

O

ƫ

V

ripple

(PK)

C

T

R2 = 1.2 kΩ

V

O

C

O

C

T

R

CL

Figure 1. Positive Regulator, Step-Up Configurations

TL497A
SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

6

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

DESIGN EQUATIONS

I

(PK)

+

2IOmax

L(mH)

+

VI–V

O

I

(PK)

ton(ms)

CT(pF)[12 ton(ms)

R1+(VO–1.2V)k

W

Choose L (50 to 500 µH), calculate
ton (10 to 150 µs)

RCL+

0.5 V
I

(PK)

CO(mF)[ton(ms)

ƪ

V

I

*

V

O

V

O

I

(PK)

)

I

O

ƫ

V

ripple

(PK)

V

I

R

CL

8101314

TL497A

1 234567

R2 = 1.2 kΩ

R1

C

O

V

O

V

I

R

CL

14 13 10

8

12 34567

TL497A

L

R1

R2 = 1.2 kΩ

EXTENDED POWER CONFIGURATION

(using external transistor)

L

V

O

C

O

C

T

C

T

BASIC CONFIGURATION

(Peak Switching Current = I

(PK)

< 500 mA)

Figure 2. Positive Regulator, Step-Down Configurations

TL497A

SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

7

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

V

I

V

I

R

CL

14 13 10 8

TL497A

12345

C

T

R1

R2 = 1.2 kΩ

C

O

R

CL

14 13 10 8

R1

C

T

L

V

O

L

V

O

12 3 45

DESIGN EQUATIONS

I

(PK)

+

2IOmaxƪ1

)

Ť

V

O

Ť

V

I

ƫ

L(mH)

+

V

I

I

(PK)

ton(ms)

CT(pF)[12 ton(ms)

R1

+

ǒ

Ť

V

O

Ť

–1.2VǓk

W

Choose L (50 to 500 µH), calculate
ton (10 to 150 µs)

RCL+

0.5 V
I

(PK)

CO(mF)[ton(ms)

ƪ

V

I

Ť

V

O

Ť

I

(PK)

)

I

O

ƫ

V

ripple

(PK)

EXTENDED POWER CONFIGURATION

(using external transistor)

†

R2 = 1.2 kΩ

†

TL497A

C

O

BASIC CONFIGURATION

(Peak Switching Current = I

(PK)

< 500 mA)

†

Use external catch diode, e.g., 1N4001, when building an inverting supply with the TL497A.

Figure 3. Inverting Applications

TL497A
SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

8

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

3-Term

Reg < 12 V

Switching

Circuit

Control

14 13

TL497A

5

V

O

V

I

V

I

V

O

R2

1 kΩ

R1

Q2

10 mA

R

CL

V

reg

14 13

5

TL497A

CURRENT LIMIT FOR EXTENDED INPUT CONFIGURATION

Q1

RCL+

V

BE(Q1)

I

limit (PK)

R1

)

V

I

I

B(Q2)

R2

+ǒV

reg

*

1Ǔ10 k

W

Control

DESIGN EQUATIONS

Switching

Circuit

EXTENDED INPUT CONFIGURATION WITHOUT CURRENT LIMIT

3-Term

Reg < 12 V

Figure 4. Extended Input Voltage Range (VI > 12 V)

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pertaining to warranty, patent infringement, and limitation of liability.

TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.

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Copyright  1999, Texas Instruments Incorporated