Datasheet

Chapter 2

SLVU803–December 2012

Detailed Description

2.1 Description

The TPS92690EVM provides a high-brightness LED driver based on the TPS92690 configured as a boost

(step-up) regulator. It is designed to operate with an input voltage in the range of 8 V to 19 V with a 12-V

nominal input voltage. This input voltage range is typical for automotive applications and common for

many off the shelf AC-DC sources. The EVM is set up for a default output current of 500 mA with an

output voltage range of 20 V to 35 V or approximately 7 to 10 LEDs, depending on the forward voltage of

each.

2.1.1 Typical Applications

This converter design describes an application of the TPS92690 as an LED driver with the specifications

listed below. For applications with a different input voltage range or different output voltage range, refer to

the TPS92690 datasheet.

2.1.2 Features

2.1.2.1 Connector Description

This section describes the connectors and test points on the EVM and how to properly connect, setup,

and use the TPS92690EVM.

2.1.2.1.1 J1, J4, J10 (VIN, GND)

These two test points and the screw down connector are for the input voltage supply to the converter. The

leads to the input supply should be twisted and kept as short as possible to minimize voltage drop,

inductance, and EMI transmission. Additional bulk capacitance between VIN and GND may be desirable if

the supply leads are greater than twelve inches, particularly if pulse width modulation (PWM) dimming will

be used. If using the screw down connector J1, pin 1 is VIN and pin 2 is GND.

2.1.2.1.2 J2, J3, J8 (LED+, LED-)

Connect the LED string between J3 and J8 with the anode of one end connected to LED+ and the

cathode of the other end connected to LED-. Alternatively, the screw down connector J2 may be used. Pin

1 of J2 is LED- and pin 2 is LED+.

2.1.2.1.3 GND

An additional ground test point is provided for ease of use. Ground leads for voltage probes, function

generators, or low power analog supplies may be connected to either GND test point.

2.1.2.1.4 PWM DIM

This test point is connected through a blocking diode to the nDIM pin of the TPS92690. Pulling this test

point to ground will disable switching and turn the LEDs off. A square wave with a low level of ground and

a high level greater than the nDIM pin threshold (greater than 1.24 V and up to 30 V) may be applied to

this test point to dim using PWM. The average LED current is approximately equal to the positive duty

cycle of the PWM signal multiplied by the steady state LED current. The PWM dimming frequency should

be between 120 Hz and 1 kHz to maintain the best linearity.

SLVU803–December 2012 Detailed Description

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