ZLED7010 Datasheet

© 2016 Integrated Device Technology, Inc.

15

April 20, 2016

4

Operating Conditions

4.1.

Thermal Conditions

Refer to section 1.1 for maximum package power dissipation specifications for the ZLED7010’s SOP-8 package.

Exceeding these specifications due to operating the chip at high ambient temperatures (see section 1.2 for

maximum operating temperature range) or driving over the maximum load current (see section 1.3) can damage

the ZLED7010. The ZLED7010 can be used for LED current applications up to750mA when properly mounted to

a high wattage land pattern. Conditions such as operating below the minimum supply voltage or inefficiency of the

circuit due to improper coil selection or excessive parasitic capacitance on the output can cause excessive chip

power dissipation.

4.2.

Thermal Shut-Down Protection

The ZLED7010 includes an on-board temperature sensing circuit that stops the output if the junction exceeds approximately

160°C.

4.3.

Open-Circuit Protection

The ZLED7010 is inherently protected if there is an open-circuit in the connection to the LEDs because in this

case, the coil is isolated from the LX pin. This prevents any back EMF from damaging the internal switch due to

forcing the drain above its breakdown voltage.

4.4.

External Temperature Compensation of Output Current

The ZLED7010’s temperature compensation feature is useful in applications that require a temperature

compensated LED control current to ensure stability and reliability over temperature, such as high luminance

LEDs. When output current compensation is needed, use an external temperature sensing network, typically with

negative temperature coefficient (NTC) thermistors/diodes, located close to the LED(s) and connected to the RNTC

and Rth inputs. With this circuit configuration, the internal circuitry of the ZLED7010 reduces the output current if

the temperature sensing input indicates a rising temperature.

Figure 4.1

Temperature Compensation

RNTC

RTH

ADJI

ADJO

GND

ZLED7010

R2

R3

NTC

R4

As shown in Figure 4.1, the temperature compensation curve is determined by R2, R3 (NTC) and R4. When the

LED temperature increases, the resistance of R3 decreases. As R3 reaches the point that R3 plus R4 equal R2,

the temperature compensation function starts to work by reducing IOUT.