ZLED7000 Datasheet

© 2016 Integrated Device Technology, Inc.

9

April 20, 2016

S

OUT

R

mV

95

I

=

2

Circuit Description

The ZLED7000 is an inductive step-down converter for driving LEDs. It operates in continuous mode, enabling proper LED

current control. The ZLED7000 supports linear or PWM control of the LED current. Only a few external components are

needed for typical applications.

2.1

Voltage Supply

The ZLED7000 has an internal regulator that disables the LX output until the voltage supply rises above a start-up

threshold voltage set internally as needed to ensure that the power MOSFET on-resistance is low enough for

proper operation. When the supply voltage exceeds the threshold, the ZLED7000 begins normal operation.

Important: The ZLED7000 must be operated within the operating voltage range specified in Table 1.2 to avoid

conditions that could result in thermal damage to the ZLED7000. Operating with the supply voltage below the

minimum can result in a high switch duty cycle and excessive ZLED7000 power dissipation, risking over-

temperature conditions (also see section 4.1 regarding thermal restrictions) that could result in activation of the

ZLED7000’s thermal shut-down circuitry. With multiple LEDs, the forward drop is typically adequate to prevent the

chip from switching below the minimum voltage supply specification (6V), so there is less risk of thermal shut-

down.

2.2

ZLED7000 Standby Mode

Whenever the ADJ pin voltage falls below 0.2V, the ZLED7000 turns the output off and the supply current drops

to approximately 60μA. This standby mode minimizes current consumption.

2.3

Output Current Control

The LED control current output on the LX pin is determined by the value of external components and the control

components are discussed in section 2.3.4. The subsequent sections describe the two options for control voltage

input at the ADJ pin: a pulse width modulation (PWM) control signal or a DC control voltage.

The ADJ pin has an input impedance

†

of 500kΩ ±25%.

2.3.1

Ω to prevent

exceeding the maximum switch current (see Table 1.1).

(1)

Where

≥0.13Ω