Datasheet

´ Full-Scale Current
LED2[7:0]
256
´ Full-Scale Current
LED1[7:0]
256
AFE4490
SBAS602F –DECEMBER 2012–REVISED OCTOBER 2013 www.ti.com
LEDCNTRL: LED Control Register (Address = 22h, Reset Value = 0000h)
D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12
0 0 0 0 0 0 LED_RANGE[1:0] LED1[7:0]
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
LED1[7:0] LED2[7:0]
This register sets the LED current range and the LED1 and LED2 drive current.
Bits D[23:18] Must be '0'
Bits D[17:16] LED_RANGE[1:0]: LED range
These bits program the full-scale LED current range for Tx. Table 7 details the settings.
Bits D[15:8] LED1[7:0]: Program LED current for LED1 signal
Use these register bits to specify the LED current setting for LED1 (default after reset is
00h).
The nominal value of the LED current is given by Equation 6,
where the full-scale LED current is either 0 mA, 50 mA, 75 mA, 100 mA, 150 mA, or 200 mA
(as specified by the LED_RANGE[1:0] register bits).
Bits D[7:0] LED2[7:0]: Program LED current for LED2 signal
Use these register bits to specify the LED current setting for LED2 (default after reset is
00h).
The nominal value of LED current is given by Equation 7,
where the full-scale LED current is either 0 mA, 50 mA, 75 mA, 100 mA, 150 mA, or 200 mA
(as specified by the LED_RANGE[1:0] register bits).
Table 7. Full-Scale LED Current across Tx Reference Voltage Settings
(1)
0.75 V (TX_REF[1:0] = 00) 0.5 V (TX_REF[1:0] = 01) 1.0 V (TX_REF[1:0] = 10)
LED_RANGE[1:0]
I
MAX
V
HR
I
MAX
V
HR
I
MAX
V
HR
00 (default after reset) 150 mA 1.4 V 100 mA 1.1 V 200 mA 1.7 V
01 75 mA 1.3 V 50 mA 1.0 V 100 mA 1.6 V
10 150 mA 1.4 V 100 mA 1.1 V 200 mA 1.7 V
11 Tx is off — Tx is off — Tx is off —
(1) For a 3-V to 3.6-V supply, use TX_REF = 0.5 V. For a 4.75-V to 5.25-V supply, use TX_REF = 0.75 V or 1.0 V.
(6)
(7)
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