ZXLD1374EST20TC Diodes Inc, ZXLD1374EST20TC Datasheet - Page 15

• Manufacturer Part Number: ZXLD1374EST20TC
• Description: LED Drivers 60V 1.5A LED Driver Converter IC
• Manufacturer: Diodes Inc

Specifications of ZXLD1374EST20TC

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ZXLD1374
Document number: DS35032 Rev. 2 - 2
Applications Information
b) Boost and Buck-boost modes
A basic ZXLD1374 application circuit for Buck-boost and Boost modes is shown in Figure 28.
Control in Boost and Buck-boost mode is achieved by
sensing the coil current in the series resistor Rs,
connected between the two inputs of a current monitor
within the control loop block.
An output from the control loop drives the input of a
comparator which drives the gate of the internal NMOS
switch transistor. In Boost and Buck-boost modes, when
the switch is on, current flows from V
switch to ground. This current ramps up until an upper
threshold value is reached. At this point the switch is
turned off and the current flows via Rs, coil, D1 and LED
back to V
When the coil current has ramped down to a lower
threshold value the switch is turned on again and the
cycle of events repeats, resulting in continuous oscillation.
The average current in the coil is equal to the average of
the maximum and minimum threshold currents and the
ripple current (hysteresis) is equal to the difference
between the thresholds.
The average current in the LED is always less than the
average current in the coil and the ratio between these
currents is set by the values of external resistors R
R
current.
current at the set level by adjusting the thresholds and the
hysteresis continuously to force the average current in the
coil to the value demanded by the voltage on the ADJ and
GI pins. This minimizes variation in output current with
changes in operating conditions. Loop compensation is
achieved by a single external capacitor C2, connected
between SHP and SGND.
For more detailed descriptions of device operation and for
choosing external components, please refer to the
application circuits and descriptions in the later sections of
this specification.
GI2
. The peak LED current is equal to the peak coil
IN
The control loop maintains the average LED
(Buck-boost mode), or GND (Boost mode).
(Continued)
IN
, via Rs, coil and
60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST
GI1
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and
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LED DRIVER CONVERTER WITH AEC-Q100
Figure 28. Boost and Buck-boost Configuration
Figure 29. Operating Waveforms
(Boost and Buck-boost Modes)
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ZXLD1374
March 2011