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| LM3409MY-NOPB Datasheet, PDF (26/43 Pages) Texas Instruments – PFET Buck Controller for High Power LED Drivers | |||
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LM3409, LM3409HV, LM3409-Q1
SNVS602J â MARCH 2009 â REVISED MAY 2013
The chosen component from step 6 is:
Q1o 3.8A,100V, DPAK
7. DIODE
Determine minimum D1 voltage rating and current rating:
VD-MAX = VIN-MAX = 75V
ID
=
(1-D)
x
ILED
=
¨¨©§1-
VO
VIN x
K¸¸¹·
x
ILED
ID = ¨©§¨1- 48V3x5V0.95¸¸¹· x1.97A = 457 mA
A 100V, 3A diode is chosen with VD = 750mV. Determine PD:
PD = ID x VD = 457 mA x 750 mV = 343 mW
The chosen component from step 7 is:
D1 o 3A,100V, SMC
8. INPUT UVLO
Solve for RUV2:
RUV2
=
VHYS
22 PA
=
1.1V
22 PA
=
50 k:
The closest 1% tolerance resistor is 49.9 k⦠therefore VHYS is:
VHYS = RUV2 x 22 PA = 49.9 k: x 22 PA = 1.1V
Solve for RUV1:
RUV1 =
1.24V x RUV2
VTURN- ON -1.24V
=
1.24V x 49.9 k:
10V -1.24V
= 7.06 k:
The closest 1% tolerance resistor is 6.98 k⦠therefore VTURN-ON is:
( ) VTURN-ON
=
1.24V x
RUV1 + RUV2
RUV1
1.24V x (6.98 k: + 49.9 k:)
VTURN-ON =
6.98 k:
= 10.1V
The chosen components from step 8 are:
RUV1 = 6.98k:
RUV2 = 49.9 k:
9. IADJ CONNECTION METHOD
The IADJ pin is left open forcing VADJ = 1.24V.
10. PWM DIMMING METHOD
PWM dimming signal pair is applied to the EN pin and GND at fDIM = 1 kHz.
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Product Folder Links: LM3409 LM3409HV LM3409-Q1
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