ILED =

200

RISNSx

mA

LM3464, LM3464A

SNVS652F – APRIL 2010 – REVISED MAY 2013

www.ti.com

Figure 18. Linear LED Current Regulator

The driving currents of the LED strings are defined by the values of RISNS1 to RISNS4 individually. The LED current

and the value of RISNSx are related by the following equation:

(10)

Since the accuracy of the LED currents are dependent on the tolerance of RISNSx, the RISNSx to recommended to

be thick carbon file resistors with no more than 1% tolerance and adequate rated power to the desired LED

current.

Figure 19. LED Current vs RISNSx

RESPONSE OF THE LM3464/64A DRIVER STAGE

In order to ensure good operation stability of the entire system, the response of the LM3464/64A circuitry must

be set slower than the primary power supply. The response of the LM3464/64A is decided by the value of the

capacitor, CDHC. In general, a higher capacitance CDHC will result in slower response of the LM3464/64A driver

stage.

Generally, a first order integrator that consists of CDHC and a transconductance amplifier with gm = 76umho and

+/– 15uA current limit as shown in Figure 20 defines the frequency response of the LM3464/64A driver stage.

14

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