MIC3003 datasheet(23/75 Pages) MICREL

23 / 75 page

Micrel, Inc.

MIC3003

November 2009

M9999-111209-C

hbwhelp@micrel.com or (408) 955-1690

RX Power

Received power is sensed as a voltage appearing at

VRX. It is assumed that this voltage is generated by a

sense resistor carrying the receiver photodiode current

or by the RSSI circuit of the receiver. The value returned

by the A/D is therefore a voltage analogous to received

power. The binary values in RXOPh and RXOPl are

related to receive power by:

RX(mW)=K x VREF x (256 x RXOPh +RXOPl/16)/ 65536 (4)

For a given implementation, the constant, K, will likely

have to be determined through experimentation or

closed-loop calibration, as it depends upon the gain and

efficiencies

the

receiver.

SFF-8472

implementations, the external calibration constants can

describe up to a fourth-order polynomial in case K is

nonlinear.

B/ Internal Calibration

If the INTCAL bit in OEMCFG3 is set to 1 (internal

calibration selected), the MIC3003 will process each

piece of data coming out of the A/D converter before

storing the result in result register. Linear slope/offset

correction will be applied on a per-channel basis to the

measured values for voltage, bias current, TX power,

and RX power. Only offset is applied to temperature.

The user must store the appropriate slope/offset

coefficients in memory at the time of transceiver

calibration. In the case of RX power, a look-up table is

provided that implements eight-segment piecewise-

linear correction. This correction may be performed as a

compensation

the

receiver

non-linearity

over

temperature or receive power level. If static slope/offset

correction for RX power is desired, the eight coefficient

sets can simply be made the same. The user has the

option to select between using preset hard-coded

delimiters values or programmable delimiters where

delimiters corresponding to the best linear approximation

intervals of a specific receiver can be entered. The latter

option will use an additional fourteen (14) bytes from the

OEM scratch pad A6h:208-221(DOh-DDh). OEMCFG6

bits [6:5] are used to select between these options. The

memory maps for the calibration coefficients are shown

in Tables 11 and 12. If the programmable delimiters

option is selected, the user must enter the seven

delimiters of the intervals that best fit the receiver

response. The diagram in Figure 3 shows the link

between the delimiters and the sets of slopes and

offsets.

Slopes Coefficients

The slopes allow for the correction of gain errors. Each

slope coefficient is an unsigned, sixteen-bit, fixed-point

binary number in the format:

[mmmmmmmm.llllllll],

(5)

where m is a data bit in the most-significant byte and l is

a data bit in the least significant byte

Slopes are always positive. The decimal point is in

between the two bytes, i.e., between bits 7 and 8. This

provides a numerical range of 1/256 (0.00391) to

255.997 in steps of 1/256. The most significant byte is

always stored in memory at the lower numerical

address.

Offset coefficients

The offsets correct for constant errors in the measured

data. Each offset, apart from temperature, is a signed,

sixteen-bit, fixed-point binary number. The bit-weights of

the offsets are the same as that of the final results. The

sixteen-bit offsets provide a numerical range of –32768

to +32767 for voltage, bias current, transmit power, and

receive power.

The numerical range for the six-bit temperature offset is

–32 (–16 °C) to +31 (+15.5 °C) in increments of .5 °C.

The two most significant bits of the temperature offset

coefficient are ignored by the MIC3003.

Computing Internal Calibration Results

Calibration of voltage, bias current, and TX power are

performed using the following calculation:

RESULTn = ADC_RESULTn x SLOPEn + OFFSETn

(6)

Calibration of RX power is performed using the following

calculation:

RESULT = ADC_RESULT x SLOPE(m) + OFFSET(m)

(7)

where m represents one of the eight linearization

intervals corresponding to the RX power level.

The results of these calculations are rounded to sixteen

bits. If the seventeenth bit is a one, the result is rounded

up to the next higher value. If the seventeenth bit is zero,

the upper sixteen bits remain unchanged. The bit-

weights of the offsets are the same as that of the final

results. For SFF-8472 compatible applications, these bit-

weights are given in Table 10.

Parameter

Magnitude of LSB

Voltage

100µV

Bias Current

2µA

TX Power

0.1µW

RX Power

0.1µW

Table 10. LSB Values of Offset Coefficients

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