ADPD1081 datasheet(32/74 Pages) AD

32 / 74 page

ADPD1080/ADPD1081

Data Sheet

Rev. C | Page 32 of 74

PD8

PD1

PD8

PD1

PD8

Figure 39. Photodiode Configuration Options for the ADPD1080 LFCSP

Table 22. Typical Photodiode Anode to Input Channel Connections for the ADPD1080 LFCSP1, 2

Input Channel

Photodiode Anode Configuration

PD1

PD2

PD3

PD4

PD5

PD6

PD7

PD8

Single Photodiode (PD1)

Two Photodiodes (PD1, PD2)

Four Photodiodes (PD1 to PD4)

Eight Photodiodes (PD1 to PD8)

Dx refers to the diode connected to the specified channel.

NC means do not connect. Leave all unused inputs floating.

LED DRIVER PINS AND LED SUPPLY VOLTAGE

The LEDX1, LEDX2, and LEDX3 pins have an absolute maximum

voltage rating of 3.6 V. Any voltage exposure over this rating

affects the reliability of the device operation and, in certain

circumstances, causes the device to cease proper operation. The

voltage of the LEDx pins must not be confused with the supply

voltages for the LED themselves. VLEDx is the voltage applied to the

anode of the external LED, whereas the LEDXx pin is the input

of the internal current driver, and the pins are connected to the

cathode of the external LED.

LED DRIVER OPERATION

The LED driver for the ADPD1080/ADPD1081 is a current

sink. The compliance voltage, measured at the driver pin with

respect to ground, required to maintain the programmed LED

current level is a function of the current required. Figure 12

shows the typical compliance voltages required at the various

LED coarse settings. Figure 40 shows the basic schematic of

how the ADPD1080/ADPD1081 connect to an LED through the

LED driver. The Determining the Average Current section and

the Determining CVLED section define the requirements for the

bypass capacitor (CVLED) and the supply voltages of the LEDs

(VLEDx).

ADPD1080/

ADPD1081

LEDXx

LGND

VLEDx

SUPPLY

CVLED

Figure 40. VLEDx Supply Schematic

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