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

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TL497A

SWITCHING VOLTAGE REGULATORS

SLVS009D – JUNE 1976 – REVISED JULY 1999

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

High Efficiency . . . 60% or Greater

Output Current . . . 500 mA

Input Current Limit Protection

TTL-Compatible Inhibit

Adjustable Output Voltage

Input Regulation . . . 0.2% Typ

Output Regulation . . . 0.4% Typ

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

. 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

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

of C

. 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

, 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.

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

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

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

AVAILABLE OPTIONS

PACKAGED DEVICES

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

3 2

1.2-V

Reference

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

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

(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),

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

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

. 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

4.5 12 V

High-level input voltage, V

INHIBIT pin 2.5 V

Low-level input voltage, V

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

TL497AC 0 70

O erating free-air tem erature range, T

TL497AI –40 85

°C

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