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OPT3002

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SBOS745A – MAY 2016 – REVISED JUNE 2016

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Copyright © 2016, Texas Instruments Incorporated

A series of result register output examples with the corresponding LSB weight and resulting optical power are

given in Table 9. Note that many combinations of exponents (E[3:0]) and fractional results (R[11:0]) can map

onto the same optical power result, as shown in the examples of Table 9.

Table 9. Examples of Decoding the Result Register into Optical Power

RESULT REGISTER

(Bits 15-0, Binary)

EXPONENT

(E[3:0], Hex)

FRACTIONAL

RESULT

(R[11:0], Hex)

LSB WEIGHT AT 505-nm

WAVELENGTH

(nW/cm2, Decimal)

RESULTING OPTICAL POWER

AT 505-nm WAVELENGTH

(nW/cm2, Decimal)

0000 0000 0000 0001b

00h

001h

1.2

1.2

0000 1111 1111 1111b

00h

FFFh

1.2

4,914

0011 0100 0101 0110b

03h

456h

9.6

338,227.2

0111 1000 1001 1010b

07h

89Ah

153.6

629,145.6

1000 1000 0000 0000b

08h

800h

307.2

629,145.6

1001 0100 0000 0000b

09h

400h

614.4

629,145.6

1010 0010 0000 0000b

0Ah

200h

1228.8

629,145.6

1011 0001 0000 0000b

0Bh

100h

2457.6

629,145.6

1011 0000 0000 0001b

0Bh

001h

2457.6

2457.6

1011 1111 1111 1111b

0Bh

FFFh

2457.6

10,063,872

To compensate for the spectral response of the device, for input wavelengths other than 505 nm, see the

Compensation for the Spectral Response section.

Note that the exponent field can be disabled (set to zero) by enabling the exponent mask (configuration register,

ME field = 1) and manually programming the full-scale range (configuration register, RN[3:0] < 1100b (0Ch)),

allowing for simpler operation in a manually-programmed, full-scale mode. Calculating optical power from the

result register contents only requires multiplying the result register by the LSB weight (in nW/cm2) associated

with the specific programmed full-scale range (see Table 8). See the low-limit register for details.

See the configuration register conversion time field (CT, bit 11) description for more information on optical power

measurement resolution as a function of conversion time.

7.6.1.1.2

Configuration Register (address = 01h) [reset = C810h]

This register controls the major operational modes of the device. This register has 11 fields, as documented in

this section. If a measurement conversion is in progress when the configuration register is written, then the active

measurement conversion immediately aborts. If the new configuration register directs a new conversion, then

that conversion is subsequently started.

Figure 20. Configuration Register

15

14

13

12

11

10

9

8

RN3

RN2

RN1

RN0

CT

M1

M0

OVF

R/W-1h

R/W-1h

R/W-0h

R/W-0h

R/W-1h

R/W-0h

R/W-0h

R-0h

7

6

5

4

3

2

1

0

CRF

FH

FL

L

POL

ME

FC1

FC0

R-0h

R-0h

R-0h

R/W-1h

R/W-0h

R/W-0h

R/W-0h

R/W-0h

LEGEND: R/W = Read/Write; R = Read only; -n = value after reset

Table 10. Configuration Register Field Descriptions

Bit

Field

Type

Reset

Description

15-12

RN[3:0]

R/W

0Ch

Range number field (read or write).

The range number field selects the full-scale optical power range of the device. The format of

this field is the same as the result register exponent field (E[3:0]); see Table 8.

When RN[3:0] is set to 1100b (0Ch), the device operates in automatic full-scale setting mode,

as described in the Automatic Full-Scale Setting Mode section. In this mode, the automatically

chosen range is reported in the result exponent (register 00h, E[3:0]).

The device powers up as 1100 in automatic full-scale setting mode.

Codes 1101b, 1110b, and 1111b (0Dh, 0Eh, and 0Fh) are reserved for future use.