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TLC5916, TLC5917

www.ti.com

SLVS695D – JUNE 2007 – REVISED JANUARY 2015

10 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

10.1 Application Information

10.1.1 Constant Current

In LED display applications, TLC591x provides nearly no current variations from channel to channel and from IC

to IC. While 5 mA

≤ IOUT ≤ 100 mA, the maximum current skew between channels is less than ±3% and between

ICs is less than ±6%.

10.1.2 Adjusting Output Current

TLC591x scales up the reference current, Iref, set by the external resistor Rext to sink a current, Iout, at each

output port. Users can follow the below formulas to calculate the target output current IOUT,target in the saturation

region. In the equations,

Rext is the resistance of the external resistor connected between the R-EXT terminal and ground and VR-EXT is the

voltage of R-EXT, which is controlled by the programmable voltage gain (VG). VG is defined by the Configuration

Code.

VR-EXT = 1.26 V × VG

(1)

Iref = VR-EXT/Rext,

(2)

IOUT,target = Iref × 15 × 3

CM – 1

(3)

The Current Multiplier (CM) determines that the ratio IOUT,target/Iref is 15 or 5. After power on, the default value of

VG is 127/128 = 0.992, and the default value of CM is 1, so that the ratio IOUT,target/Iref = 15. Based on the default

VG and CM:

VR-EXT = 1.26 V × 127/128 = 1.25 V

(4)

IOUT,target = (1.25 V/Rext) × 15

(5)

Therefore, the default current is approximately 52 mA at 360

Ω and 26 mA at 720 Ω. The default relationship

after power on between IOUT,target and Rext is shown in Figure 19.

Figure 19. Default Relationship Curve Between IOUT,target and Rext After Power Up

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