LM3402HVEVAL National Semiconductor, LM3402HVEVAL Datasheet - Page 17
![BOARD EVALUATION FOR LM3402HV](/photos/28/39/283984/lm3402hveval_sml.jpg)
LM3402HVEVAL
Manufacturer Part Number
LM3402HVEVAL
Description
BOARD EVALUATION FOR LM3402HV
Manufacturer
National Semiconductor
Series
PowerSmart®r
Specifications of LM3402HVEVAL
Current - Output / Channel
500mA
Outputs And Type
1, Non-Isolated
Voltage - Output
4 V
Features
Dimmable
Voltage - Input
6 ~ 75 V
Utilized Ic / Part
LM3402
Core Chip
LM3402HV
Topology
Buck
Input Voltage
6V To 75V
Dimming Control Type
PWM
Kit Contents
Board
Svhc
No SVHC (15-Dec-2010)
Kit Features
Cycle-by-Cycle Current Limit, Separate PWM Dimming
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
*LM3402HVEVAL
Adding a resistor in series with the CS pin causes the ob-
served output LED current to shift very slightly. The reason
for this is twofold: (1) the CS pin has about 20pF of inherent
capacitance inside it which causes a slight delay (20ns for a
1kΩ series resistor), and (2) the comparator that is watching
the voltage at the CS pin uses a pnp bipolar transistor at its
input. The base current of this pnp transistor is approximately
100nA which will cause a 0.1mV change in the 200mV thresh-
old. These are both very minor changes and are well under-
stood. The shift in current can either be neglected or taken
into consideration by changing the current sense resistance
slightly.
CS PIN PROTECTION WITH OVP
When designing output overvoltage protection into the switch-
ing converter circuit using a zener diode, transient protection
FIGURE 7. CS Pin, Transient Path with Protection
17
on the CS pin requires additional consideration. As shown in
Figure
(with the series resistor) for output overvoltage protection will
now again allow the transient energy to be passed through
the CS pin’s ESD structure thereby damaging it.
Adding an additional series resistor to the CS pin as shown
in
pass through the sense resistor thereby protecting the
LM340X device.
Figure 9
8, adding a zener diode from the output to the CS pin
will result in the majority of the transient energy to
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