ZXLD1352ET5TA Diodes Zetex, ZXLD1352ET5TA Datasheet

Page 1

Description The ZXLD1352 is a continuous mode inductive step-down converter with integrated switch and high side current sense. It operates from an input supply from 7V to 30V driving single and multiple series connected LEDs effciently externally adjustable output current ...

Page 2

Block Diagram ADJ Vref GND Pin Description Name Pin No. Description LX 1 Drain of NDMOS switch GND 2 Ground (0V) Multi-function On/Off and brightness control pin: • Leave floating for normal operation =0.1/R OUTnom ...

Page 3

Absolute Maximum Ratings Symbol Input Voltage Voltage SENSE SENSE LX Output Voltage V LX Adjust Pin Input Voltage V ADJ I Switch Output Current LX Power Dissipation P TOT (Refer to Package thermal de-rating curve on ...

Page 4

Electrical Characteristics (Test conditions: V Symbol Parameter V Internal regulator start-up threshold SU Quiescent supply current I INQoff with output off Quiescent supply current I INQon with output switching Mean current sense threshold voltage V SENSE (defines LED current setting ...

Page 5

Device Description The device, in conjunction with the coil (L1) and current sense resistor (RS), forms a self-oscillating continuous-mode buck converter Device operation (Refer to block diagram and Figure 1 - Operating waveforms) Operation can be best understood by assuming ...

Page 6

Device Description voltage SENSE voltage Coil current 0V Comparator V input voltage ADJ 5V Comparator output 0V ZXLD1352 Document number: DS33469 Rev Toff Ton 115mV 85mV 0.15V ADJ Figure 2. Operating ...

Page 7

Typical Operating Waveforms Normal Operation. Output Current (Ch3) and LX Voltage (Ch1 Ch3 100mA Ch 2 20.0V Start-up Waveforms. Output Current (Ch3), LX Voltage (Ch2) ZXLD1352 Document number: DS33469 Rev Diodes Incorporated [V = 12V, ...

Page 8

Typical Characteristics For typical application circuit driving 1W Luxeon ...

Page 9

Typical Characteristics (Cont ...

Page 10

Typical Characteristics (Cont ...

Page 11

Typical Characteristics (Cont.) ZXLD1352 Document number: DS33469 Rev Product Line of Diodes Incorporated www.diodes.com ZXLD1352 December 2010 © Diodes Incorporated ...

Page 12

Application Information Setting nominal average output current with external resistor R The nominal average output current in the LED(s) is determined by the value of the external current sense resistor (R connected between V and I and is given by: ...

Page 13

Application Information (Continued) Output Current Adjustment by PWM Control Directly driving ADJ input A Pulse Width Modulated (PWM) signal with duty cycle D output current to a value above or below the nominal average value set by resistor R   ...

Page 14

Application Information (Continued) Shutdown Mode Taking the ADJ pin to a voltage below 0.2V will turn off the output and supply current will fall to a low standby level of 20µA nominal. Note that the ADJ pin is not a ...

Page 15

Application Information (Continued) Inductor Selection Recommended inductor values for the ZXLD1352 are in the range 47µH to 220µH. Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in ...

Page 16

Application Information (Continued) Example For V =12V, L=47μH, rL=0.64Ω LED T = (47e-6 x 0.105)/(12 - 3.4 - 0.672) = 0.622μ (47e-6 x 0.105)/(3.4 + 0.36 + 0.322)= 1.21μs OFF This gives an operating frequency ...

Page 17

Application Information (Continued) Reducing Output Ripple Peak to peak ripple current in the LED can be reduced, if required, by shunting a capacitor C below:   value of 1µF will reduce nominal ripple current by a ...

Page 18

Application Information (Continued) Note that the device power dissipation will most often be a maximum at minimum supply voltage. It will also increase if the efficiency of the circuit is low. This may result from the use of unsuitable coils, ...

Page 19

Dimming Output Current Using PWM When the ADJ pin is driven with a low frequency PWM signal (eg 100Hz), with a high level voltage V the output current will be switched on and off at the PWM frequency, resulting in ...

Page 20

... Ordering Information Device Package ZXLD1352ET5TA TSOT23-5 Package Outline Dimensions TSOT23-5 ZXLD1352 Document number: DS33469 Rev Product Line of Diodes Incorporated Reel Size Tape Width (mm) (mm) 180 www.diodes.com ZXLD1352 Quantity Part (per reel) Marking 3000 1352 December 2010 © Diodes Incorporated ...

Page 21

DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY ...