AFS090 datasheet(112/334 Pages) MICROSEMI

112 / 334 page

Device Architecture

2- 96

R e visio n 2

The diode’s voltage is measured at each current level and the temperature is calculated based on EQ 7.

EQ 7

where

ITMSLO is the current when the Temperature Strobe is Low, typically 100 µA

ITMSHI is the current when the Temperature Strobe is High, typically 10 µA

VTMSLO is diode voltage while Temperature Strobe is Low

VTMSHI is diode voltage while Temperature Strobe is High

is the non-ideality factor of the diode-connected transistor. It is typically 1.004 for the Microsemi-

recommended transistor type 2N3904.

= 1.3806 x 10-23 J/K is the Boltzman constant

= 1.602 x 10-19 C is the charge of a proton

When I

TMSLO / ITMSHI = 10, the equation can be simplified as shown in EQ 8.

EQ 8

In the Fusion TMB, the ideality factor n for 2N3904 is 1.004 and

ΔV is amplified 12.5 times by an internal

amplifier; hence the voltage before entering the ADC is as given in EQ 9.

EQ 9

This means the temperature to voltage relationship is 2.5 mV per degree Kelvin. The unique design of

Fusion has made the Temperature Monitor System simple for the user. When the 10-bit mode ADC is

used, each LSB represents 1 degree Kelvin, as shown in EQ 10. That is, e. 25°C is equal to 293°K and is

represented by decimal 293 counts from the ADC.

EQ 10

If 8-bit mode is used for the ADC resolution, each LSB represents 4 degrees Kelvin; however, the

resolution remains as 1 degree Kelvin per LSB, even for 12-bit mode, due to the Temperature Monitor

design. An example of the temperature data format for 10-bit mode is shown in Table 2-38.

Table 2-38 • Temperature Data Format

Temperature

Temperature (K)

Digital Output

(ADC 10-bit mode)

–40°C

233

00 1110 1001

–20°C

253

00 1111 1101

0°C

273

01 0001 0001

1°C

274

01 0001 0010

10 °C

283

01 0001 1011

25°C

298

01 0010 1010

50 °C

323

01 0100 0011

85 °C

358

01 0110 0110

VTMSLO VTMSHI

–

-------

ITMSLO

ITMSHI

-----------------

⎝⎠

⎛⎞

ΔVV

TMSLO

VTMSHI

–

1.986 10

–

ADC

ΔV 12.5

2.5 mV KT

()

⁄

2.5 mV

2.56 V

-----------------

1 LSB

AFS090 Datasheet(PDF) 112 Page - Microsemi Corporation

AFS090 Datasheet(HTML) 112 Page - Microsemi Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL