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TL497AY Datasheet(PDF) 1 Page - Texas Instruments |
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TL497AY Datasheet(HTML) 1 Page - Texas Instruments |
1 / 11 page TL497AC, TL497AI, TL497AY SWITCHING VOLTAGE REGULATORS SLVS009C – JUNE 1976 – REVISED AUGUST 1995 Copyright © 1995, Texas Instruments Incorporated 4–1 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 TL497AC and TL497AI incorporate on a single monolithic chip all the active functions required in the construction of switching voltage regulators. They can also be used as the control element to drive external components for high-power-output applications. The TL497AC and TL497AI were designed for ease of use in step-up, step-down, or voltage inversion applications requiring high efficiency. The TL497AC and TL497AI are fixed-on-time variable-frequency switching-voltage-regulator control circuits. 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 VCC. 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 SUBSTRATE) 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 CT as described above. The internal pass transistor is driven on during the charging of CT. The internal transistor may 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 is also available for blocking or commutating purposes. The TL497AC and TL497AI also have 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, RCL, 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. AVAILABLE OPTIONS T PACKAGED DEVICES CHIP TA SURFACE MOUNT (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 — — 1 2 3 4 5 6 7 14 13 12 11 10 9 8 COMP INPUT INHIBIT FREQ CONTROL SUBSTRATE GND CATHODE ANODE VCC CUR LIM SENS BASE DRIVE† BASE† COL OUT NC EMIT OUT (TOP VIEW) TL497AC, TL497AI . . . D, N, OR PW PACKAGE NC – No internal connection † BASE (11) and BASE DRIVE (12) are used for device testing only. They are not normally used in circuit applications of the device. 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. |
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