TSC2046E datasheet(13/34 Pages) TI2

13 / 34 page

TSC2046E

SBAS417B − JUNE 2007 − REVISED JANUARY 2008

www.ti.com

The second mode of operation does not require a test

temperature calibration, but uses a two-measurement

method to eliminate the need for absolute temperature

calibration and for achieving 2

°C accuracy. This mode

requires a second conversion with an address of A2 = 1,

A1 = 1, and A0 = 1, with a 91 times larger current. The voltage

difference between the first and second conversion using 91

times the bias current is represented by Equation (1):

DV + kT

q @ In(N)

where:

N is the current ratio = 91

k = Boltzmann’s constant = 1.3807

× 10−23 J/K

(joules/kelvins).

q = the electron charge = 1.6022

× 10–19 C (coulombs).

T = the temperature in kelvins (K).

This method can provide improved absolute temperature

measurement, but at a lower resolution of 1.6

°C/LSB. The

resulting equation that solves for T is:

@ DV

@ In(N)

where:

∆V = VBE(TEMP1) – VBE(TEMP0) (in mV)

∴ T = 2.573 ⋅ ∆V (in K)

or T = 2.573

⋅ ∆V – 273 (in °C)

NOTE: The bias current for each diode temperature

measurement is only on for three clock cycles (during the

acquisition mode) and, therefore, does not add any

noticeable increase in power, especially if the temperature

measurement only occurs occasionally.

BATTERY MEASUREMENT

An added feature of the TSC2046E is the ability to monitor

the battery voltage on the other side of the voltage regulator

(dc/dc converter), as shown in Figure 7. The battery voltage

can vary from 0V to 6V, while maintaining the voltage to the

TSC2046E at 2.7V, 3.3V, etc. The input voltage (VBAT) is

divided down by four so that a 5.5V battery voltage is

represented as 1.375V to the ADC. This design simplifies the

multiplexer and control logic. In order to minimize the power

consumption, the divider is only on during the sampling

period when A2 = 0, A1 = 1, and A0 = 0 (see Table 1 for the

relationship between the control bits and configuration of the

TSC2046E).

+VCC

VBAT

7.5k

Ω

2.5k

Ω

DC/DC

Converter

Battery

0.5V

5.5V

0.125V to 1.375V

2.7V

ADC

Figure 7. Battery Measurement Functional Block

Diagram

(1)

(2)

TSC2046E Datasheet(PDF) 13 Page - Texas Instruments

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