ZLED7x30 Datasheet

© 2016 Integrated Device Technology, Inc.

12

April 20, 2016

Rs

V

1

.

0

I

2

Circuit Description

2.1

ZLED7x30 Overview

The ZLED7x30 is a continuous-mode inductive step-down converter LED driver for driving single or multiple series-

connected LEDs from a voltage input higher than the LED voltage (Vin = 8.5 to 40VDC; see section 3.2.2 for

important details). The ZLED7x30 provides an adjustable output current (1.2A maximum for ZLED7030; 1.0A

maximum for ZLED7330; 0.75A maximum for ZLED7530; 0.35A maximum for ZLED7730) , which is nominally set via

an external sense resistor Rs and controlled by the ZLED7x30’s integrated high-side output current-sensing circuit

and output switch. The ZLED7x30 detects external switching action on the supply line to adjust the output current in

different modes on different levels.

Only a resistor, a diode, an inductor, and three capacitors are needed for a typical basic application. Refer to the

application circuits in section 3 for the location of the components referred to in the following sections.

2.2

Control of Output Current via External Sense Resistor Rs

the nominal average output current. Equation (1) can be used to calculate the nominal output current, which is the LX

typical basic application and section 3.4 for layout guidelines for Rs.

(1)

2.3

Multi-Mode Switch Dimming

The ZLED7x30 detects external switching action on the supply line to adjust output current, allowing dimming

functionality to be achieved without changing the original lighting system circuitry. The switch dimming is implemented

in either two-level mode or three-level mode. The output current of each level and the total number of levels are

customer selected by setting the corresponding input conditions on the DIM1 and DIM2 pins. See page 1 for a typical

application using the DIM1 and DIM2 pins.

The output current is set at the initial 100% value determined by the sense resistor Rs the first time that power is

supplied to the chip. After the initial power up sequence, the chip adjusts the output current according to the external

switch action. After the lowest current level, the current cycles back to the initial value if subsequent switch action is

detected. If the power is switched off for longer than 2 seconds, the device will return to its initial state and the output

current will be set to the initial value the next time that power is applied.

There are two types of switch action: a normal switch, which has an off-time between each subsequent switch action

longer than 2s, and a dimming switch, which has an off-time between each subsequent switch less than 2s.