ZXLD1374_11 DIODES [Diodes Incorporated], ZXLD1374_11 Datasheet - Page 30

• Manufacturer Part Number: ZXLD1374_11
• Description: 60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST
• Manufacturer: DIODES [Diodes Incorporated]

ZXLD1374
Document number: DS35032 Rev. 2 - 2
Applications Information
Over-voltage Protection
The ZXLD1374 is inherently protected against open-circuit load when used in Buck configuration. However care has to be
taken with open-circuit load conditions in Buck-boost or Boost configurations. This is because in these configurations there
is only an over-voltage FLAG but no internal open-circuit protection mechanism for the internal MOSFET. In this case an
Over-Voltage-Protection (OVP) network should be provided to the MOSFET to avoid damage due to open circuit conditions.
This is shown in Figure 37 below, highlighted in the dotted blue box.
The zener voltage is determined according to: V
Q1 will rise turning Q1 on. This will pull the PWM pin low and disable the LX output until the voltage on the LX falls below
Vz. If the LX pin remains above V
Care should be taken such that the maximum gate voltage of the Q1 MOSFET is not exceeded.
An alternative,solution for OVP function is to use the diagnostic section of the ZXLD1374 to initiate the disabling of the LX
pin. For example, a microcontroller could be used to respond to the FLAG and the status pins, and if an over-voltage state is
indicated, the microcontroller could switch the device off by pulling the PWM signal low.
Z
for longer than 20ms then the ZXLD1374 will enter into a shutdown state.
(Continued)
60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST
Z
Figure 50. OVP Circuit
= V
www.diodes.com
LEDMAX
30 of 37
LED DRIVER CONVERTER WITH AEC-Q100
+10%. If the LX pin voltage exceeds V
Diodes Incorporated
A Product Line of
Z
the gate of MOSFET
© Diodes Incorporated
ZXLD1374
March 2011