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PDF ZXLD1350Q Data sheet ( Hoja de datos )
| Número de pieza | ZXLD1350Q | |
| Descripción | AUTOMOTIVE GRADE 350mA BUCK LED DRIVER | |
| Fabricantes | Diodes | |
| Logotipo |  |
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A Product Line of
Diodes Incorporated
ZXLD1350Q
AUTOMOTIVE GRADE 350mA BUCK LED DRIVER
Description
The ZXLD1350Q is a hysteretic 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 or
multiple series connected LEDs efficiently external adjustable output
current up to 350mA.
The output current can be adjusted by applying a DC voltage or a
PWM waveform. 100:1 adjustment of output current is possible using
PWM control. Applying a voltage of 0.2V or lower to the ADJ pin
turns the output off and switches the device into a low current
standby state.
The ZXLD1350Q has been qualified to AECQ100 grade 2 and is
Automotive Grade supporting PPAPs.
Pin Assignments
LX
GND
ADJ
TSOT23-5
Top View
VIN
ISENSE
Features
Simple low parts count
Internal 30V NDMOS switch
Internal PWM filter
High efficiency (up to 95% (Note 1)
Wide input voltage range: 7V to 30V
40V transient capability
Up to 1MHz switching frequency
Typical 4% output current accuracy
Green Molding (No Br, Sb) in TSOT25
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Automotive Grade
Qualified to AEC-Q100 Standards for High Reliability
Supports PPAP Documents (Note 4)
Notes: 1.
2.
3.
4.
No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free,
"Green" and Lead-free.
Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl)
and <1000ppm antimony compounds.
Automotive products are AEC-Q100 qualified and are PPAP capable. Automotive, AEC-Q100 and standard products are electrically and thermally
the same, except where specified. For more information, please refer to http://www.diodes.com/quality/product_compliance_definitions/.
Typical Application Circuit
ZXLD1350Q
Document number: DS37076 Rev. 1 - 2
VIN
7~30V
C1
1µF
GND
RS
0.33
L1
47µH
VIN SET
ADJ ZXLD1350
GND
LX
1 of 19
www.diodes.com
December 2014
© Diodes Incorporated
1 page  
A Product Line of
Diodes Incorporated
ZXLD1350Q
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)
Figure 1. Theoretical Operating Waveforms
Operation can be best understood by assuming that the ADJ pin of the device is unconnected and the voltage on this pin (VADJ) appears
directly at the (+) input of the comparator.
When input voltage VIN is first applied, the initial current in L1 and RS is zero and there is no output from the current sense circuit. Under this
condition, the (-) input to the comparator is at ground and its output is high. This turns MN on and switches the LX pin low, causing current to
flow from VIN to ground, via RS, L1 and the LED(s). The current rises at a rate determined by VIN and L1 to produce a voltage ramp (VSENSE)
across RS. The supply referred voltage VSENSE is forced across internal resistor R1 by the current sense circuit and produces a proportional
current in internal resistors R2 and R3. This produces a ground referred rising voltage at the (-) input of the comparator. When this reaches
the threshold voltage (VADJ), the comparator output switches low and MN turns off. The comparator output also drives another NMOS switch,
which bypasses internal resistor R3 to provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 15% of VADJ.
When MN is off, the current in L1 continues to flow via D1 and the LED(s) back to VIN. The current decays at a rate determined by the LED
and diode forward voltages to produce a falling voltage at the input of the comparator. When this voltage returns to VADJ, the comparator
output switches high again. This cycle of events repeats, with the comparator input ramping between limits of VADJ ± 15%.
ZXLD1350Q
Document number: DS37076 Rev. 1 - 2
5 of 19
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December 2014
© Diodes Incorporated
5 Page 
A Product Line of
Diodes Incorporated
ZXLD1350Q
Application Information (Continued)
Output Current Adjustment by PWM Control
Directly driving ADJ input
A Pulse Width Modulated (PWM) signal with duty cycle DPWM can be applied to the ADJ pin, as shown below, to adjust the output current to
a value above or below the nominal average value set by resistor RS:
VADJ
PWM
ADJ ZXLD1350
0V GND
GND
Driving the ADJ input via open collector transistor
The recommended method of driving the ADJ pin and controlling the amplitude of the PWM waveform is to use a small NPN switching
transistor as shown below:
PWM
ADJ ZXLD1350
GND
GND
This scheme uses the 200k resistor between the ADJ pin and the internal voltage reference as a pull-up resistor for the external transistor.
Driving the ADJ input from a microcontroller
Another possibility is to drive the device from the open drain output of a microcontroller. The diagram below shows one method of doing this:
MCU
10k
ADJ ZXLD1350
GND
The diode and resistor suppress possible high amplitude negative spikes on the ADJ input resulting from the drain-source capacitance of the
FET. Negative spikes at the input to the device should be avoided as they may cause errors in output current, or erratic device operation.
PWM dimming can be further split into high frequency and low frequency PWM dimming and how the device responds to these.
ZXLD1350Q
Document number: DS37076 Rev. 1 - 2
11 of 19
www.diodes.com
December 2014
© Diodes Incorporated
11 Page | ||
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| PDF Descargar | [ Datasheet ZXLD1350Q.PDF ] | |
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