MAX1234ETI+T Maxim Integrated Products, MAX1234ETI+T Datasheet - Page 32

• Manufacturer Part Number: MAX1234ETI+T
• Description: IC CNTRLR TOUCH 28-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Resistiver

Specifications of MAX1234ETI+T

• Touch Panel Interface: 4-Wire
• Number Of Inputs/keys: 1, 4 x 4 Keypad
• Resolution (bits): 8, 10, 12 b
• Data Interface: MICROWIRE™, QSPI™, Serial, SPI™
• Data Rate/sampling Rate (sps, Bps): 50k
• Voltage Reference: Internal
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Applications: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Two auxiliary analog inputs (AUX1 and AUX2) allow the
MAX1233/MAX1234 to monitor analog input voltages
from zero to V
auxiliary input reading.
The MAX1233/MAX1234 provide two temperature mea-
surement options: a single-ended conversion method
and a differential conversion method. Both temperature
measurement techniques rely on the semiconductor
junction’s operational characteristics at a fixed current
level. The forward diode voltage (V
a well-defined characteristic. The ambient temperature
can be predicted in applications by knowing the value
of the V
toring the delta of that voltage as the temperature
changes. Figure 17 illustrates the functional block of the
internal temperature sensor.
The single conversion method requires calibration at a
known temperature, but only requires a single reading to
predict the ambient temperature. First, the internal diode
forward bias voltage is measured by the ADC at a
known temperature. Subsequent diode measurements
provide an estimate of the ambient temperature through
extrapolation. This assumes a temperature coefficient of
-2.1mV/°C. The single conversion method results in a
resolution of 0.29°C/LSB (2.5V reference) and
0.12°C/LSB (1.0V reference) with a typical accuracy of
±2°C. Figure 18 shows the flowchart for the single tem-
perature measurement.
The differential conversion method uses two measure-
ment points. The first measurement is performed with a
fixed bias current into the internal diode. The second
measurement is performed with a fixed multiple of the
original bias current. The voltage difference between the
first and second conversion is proportional to the
absolute temperature and is expressed by the following
formula:
where:
ΔV
N = current ratio of the second measurement to the first
measurement
k = Boltzmann’s constant (1.38 × 10
q = electron charge (1.60 × 10
T = temperature in °Kelvin
The resultant equation solving for °K is:
T(°K) = q x ΔV / (k × ln(N))
32
BE
______________________________________________________________________________________
= difference in diode voltage
BE
voltage at a fixed temperature and then moni-
REF
ΔV
. Figure 16 illustrates the process of
Temperature Measurements
BE
= (kT/q)
Auxiliary Analog Inputs
-19
✕
ln(N)
C)
BE
-23
) vs. temperature is
eV/°Kelvin)
Figure 16. Auxiliary Input Flowchart
Figure 17. Internal Block Diagram of Temperature Sensor
TEMP1
NO
NO
STORE AUXILIARY INPUT 1 OR 2 IN
AUX1 OR AUX2 REGISTER
AUXILIARY INPUT 1 OR 2
POWER UP REFERENCE
AUTO POWER-DOWN
CONTROL REGISTER
AVERAGING DONE?
TEMP2
REFERENCE IN
HOST WRITES
START CLOCK
POWER UP
CONVERT
SET BUSY
IS DATA
MODE?
IS ADC
ADC
LOW
ADC
YES
YES
MUX
AUXILIARY INPUT 1 OR
POWER DOWN REFERENCE
AUXILIARY INPUT 2
TURN OFF CLOCK
SET BUSY HIGH
POWER DOWN
DONE
ADC
CONVERTER
A/D