TL494 pin functions/configuration/ratings/operating conditions/layout diagram

IC TL494 is designed for single chip pulse width modulation application circuits. This device is mainly used in power supply control circuits which can be dimensioned efficiently using this IC.

The device contains a variable oscillator, a dead-time controller stage (DTC), a trigger control for pulse steering, a precision 5 V regulator, two error amplifiers, and some output buffering circuitry.

The common-mode voltage range of the error amplifier is -0.3 V to VCC - 2V.

The dead-time control comparator is set with a fixed offset value to provide a constant dead-time of approximately 5%.

The on-chip oscillator function can be overridden by connecting the IC's RT pin #14 to the reference pin #14 and supplying a sawtooth signal externally to CT pin #5. This facility also allows synchronous driving of many TL494s with different supply rails.

IC.

The output transistors with floating outputs inside the chip are arranged to provide common emitter output or emitter follower output facilities.

The device allows the user to obtain either push-pull or single-ended oscillation on the output pins by appropriately configuring pin #13 (output control function pin).

Internal circuitry makes it impossible for any output to produce double pulses, and the IC uses push-pull functionality.

Pin Function and Configuration

The following diagram and description provide us basic information about the functionality of the pins of IC TL494.

Pin #1 and Pin #2 (1 IN+ and 1 IN-): These are the non-inverting and inverting inputs of the error amplifier (op amp 1).

Pin #16, Pin #15 (1 IN+ and 1 IN-): As mentioned above, these are the non-inverting and inverting inputs of the error amplifier (op amp 2).

Pin #8 and Pin #11 (C1, C2): These are outputs 1 and 2 of the IC and they are connected to the collectors of the respective internal transistors.

Pin #5 (CT): This pin needs to be connected to an external capacitor to set the oscillator frequency.

Pin #6 (RT): This pin needs to be connected to an external resistor to set the oscillator frequency.

Pin #4 (DTC): This is the input to the internal op amp that controls the dead time operation of the IC.

Pin #9 and Pin #10 (E1 and E2): These are the outputs of the IC and are connected to the emitter pin of the internal transistor.

Pin #3 (Feedback): As the name implies, this input pin is used to integrate with the output sample signal to achieve the desired automatic control of the system.

Pin #7 (Ground): This pin is the ground pin of the IC and needs to be connected to 0 V of the power supply.

Pin #12 (VCC): This is the positive power supply pin for the IC.

Pin #13 (O/P CNTRL): This pin can be configured to enable the output of the IC in either push-pull mode or single-ended mode.

Pin #14 (REF): This output pin provides a constant 5V output and can be used to fix the reference voltage for the error op amp in comparator mode.

Absolute Maximum Ratings

(VCC) Maximum supply voltage not to exceed = 41 V

(VI) Maximum voltage on input pins does not exceed = VCC + 0.3 V

(VO) Maximum output voltage at the collector of the internal transistor = 41 V

(IO) Maximum current on internal transistor collector = 250 mA

Maximum IC lead soldering heat at 1.6 mm (1/16 inch) from IC body not to exceed 10 seconds @ 260 °C

Tstg Storage temperature range = –65/150 °C

Recommended operating conditions

The following data gives you the recommended voltages and currents that can be used to operate the IC under safe and efficient conditions:

VCC power supply: 7 V to 40 V

VI amplifier input voltage: -0.3 V to VCC - 2 V

VO transistor collector voltage = 40, collector current of each transistor = 200 mA

Feedback pin current: 0.3 mA

fOSC oscillator frequency range: 1 kHz to 300 kHz

CT Oscillator timing capacitor value: between 0.47 nF and 10000 nF

RT Oscillator Timing Resistor Value: Between 1.8 k and 500 k ohms.

Internal layout