LM3464MH National Semiconductor, LM3464MH Datasheet - Page 18

• Manufacturer Part Number: LM3464MH
• Description: IC, LED DRIVER, BUCK, 28TSSOP
• Manufacturer: National Semiconductor

Specifications of LM3464MH

• No. Of Outputs: 4
• Input Voltage: 12V To 80V
• Driver Case Style: TSSOP
• Svhc: No SVHC (15-Dec-2010)
• No. Of Pins: 28
• Operating Temperature Range: -40°C To +125°C
• Topology: Linear
• Efficiency: 98%
• Led Driver Application: Streetlights, Solid State Lighting Solutions
• Dimming Control Type: PWM / Analogue
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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verse current of the CMHZ5267B is specified 1.7mA at 75V
zener voltage. The maximum allowable reverse current is
6.67mA as the power rating of the CMHZ5276B is 500mW.
Given that the input current of the DRx pins of the
LM3464/64A at 100V is 63uA maximum, if the DRx pin volt-
age is below 100V the current flows into the DRx pin (I
below 63uA. In order to reserve operation margin for compo-
nent variations, I
calculations.
Because V
pins, the maximum resistance of R
lowing this equation:
Where V
zener diode Zx respectively.
For V
And the minimum value of R
Thus, the value of R
To minimize power dissipation on the zener diodes, a stan-
dard 42.2kΩ resistor can be used for the R
resistors, R
by the voltage difference between V
mum power dissipation on every R
RAIL(peak)
Z
RAIL(peak)
and I
DRx
= 150V, the maximum value of R
are used to absorb the power being introduced
Z
DRx
are the reverse voltage and current of the
is the possible highest voltage at the DRx
is assumed equal to 63uA in the following
DRx
must be selected in the range:
DRx
is:
DRx
DRx
RAIL
equals to:
can be obtained fol-
and V
DRx
. Because the
DRx
Zx
, the maxi-
is:
DRx
) is
18
Thus, a standard 42.2kΩ resistor with 0.25W power rating
(1206 package) and 1% tolerance can be used.
Calculating the Values of Z
Similar to the requirements of selecting the Zx and R
voltage at the VIN pin of the LM3464/64A is clamped to 75V
by a voltage clamping circuit consists of Z
the maximum operating and shut-down current (V
are 3mA and 700uA respectively, in order to ensure the volt-
age of the VIN pin is clamped close to 75V even when the
LM3464/64A is disabled, a 1.5W/75V zener diode CMZ5946B
from Central Semiconductor is used to ensure adequate con-
duction current for Z
is specified 5mA at 75V, so the allowable current flows
through Z
The value of R
Maximum value of R
Minimum value of R
So the value of R
To minimize power dissipations on both the Z
standard 9.31kΩ resistor can be selected for the R
the maximum power dissipation on R
Thus, a standard 9.38kΩ resistor with 2512 package (1W)
and 1% tolerance can be used.
IN
is in between 5mA to 20mA.
IN
is governed by the following equations:
IN
must be in the range:
IN
IN
IN
. The reverse current of the CMZ5946B
:
:
IN
and R
IN
IN
:
is:
IN
and R
IN
IN
and R
EN
. Because
IN
DRx
< 2.1V)
. Then
, the
IN
, a