DS1856E-050 Maxim Integrated Products, DS1856E-050 Datasheet - Page 26

• Manufacturer Part Number: DS1856E-050
• Description: Digital Potentiometer ICs
• Manufacturer: Maxim Integrated Products

Specifications of DS1856E-050

• Number Of Pots: Dual
• Taps Per Pot: 256
• Resistance: 50 KOhms
• Wiper Memory: Non Volatile
• Digital Interface: Serial (2-Wire)
• Operating Supply Voltage: 3.3 V, 5 V
• Supply Current: 2 mA
• Maximum Operating Temperature: + 95 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2.85 V
• Package / Case: TSSOP-16
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Dual, Temperature-Controlled Resistors with Inter-
nally Calibrated Monitors and Password Protection
The gain register is now set and the resolution of the
conversion will best match the expected LSB. The next
step is to calibrate the offset of the DS1856. With the
correct gain value written to the gain register, again
force the null input to the pin. Read the digital result
from the part (Meas1). The offset value is equal to the
negative value of Meas1.
The calculated offset is now written to the DS1856 and
the gain and offset scaling is now complete.
The right-shifting method is used to regain some of the
lost ADC range of a calibrated system. If a system is cali-
brated so the maximum expected input results in a digi-
tal output value of less than 7FFFh (1/2 FS), then it is a
candidate for using the right-shifting method.
If the maximum desired digital output is less than 7FFFh,
then the calibrated system is using less than 1/2 of the
ADC’s range. Similarly, if the maximum desired digital
output is less than 1FFFh, then the calibrated system is
only using 1/8 of the ADC’s range. For example, if using
a zero for the right-shift during internal calibration and
the maximum expected input results in a maximum digi-
tal output less than 1FFCh, only 1/8 of the ADC’s range is
used. If left like this, the three MS bits of the ADC will
never be used. In this example, a value of 3 for the right-
shifting maximizes the ADC range. No resolution is lost
since this is a 12-bit converter that is left justified. The
26
____________________________________________________________________
Right-Shifting A/D Conversion Result
Offset
If Meas2 >= Clamp then
Else
end;
Set the gain register to gain_result;
_Re
(Scalable Dynamic Ranging)
gain_result = gain_result + 2^n;
Force the 90% FS input (2.949075V);
Meas2 = read the digital result from
the part;
gain_result = gain_result – 2^n;
Force the null input (0.5V);
Meas1 = read the digital result from
the part;
if (Meas2 – Meas1) > (CNT2 –
CNT1) then
gain_result = gain_result – 2^n;
gister
Meas
4
1
value can be right-shifted four times without losing reso-
lution. Table 9 shows when the right-shifting method can
be used.
The direct-to-digital temperature sensor measures tem-
perature through the use of an on-chip temperature
measurement technique with a -40°C to +102°C operat-
ing range. Temperature conversions are initiated upon
power-up, and the most recent conversion is stored in
memory locations 60h and 61h of the Main Device,
which are updated every t
sions do not occur during an active read or write to
memory.
The value of each resistor is determined by the tempera-
ture-addressed look-up table. The look-up table assigns
a unique value to each resistor for every 2°C increment
with a 1°C hysteresis at a temperature transition over the
operating temperature range (see Figure 4).
Table 9. Right Shifting
Figure 4. Look-Up Table Hysteresis
WITH ZERO RIGHT-SHIFTS
OUTPUT RANGE USED
0h....FFFFh
0h....7FFFh
0h....3FFFh
0h....1FFFh
0h....0FFFh
M6
M5
M4
M3
M2
M1
2
4
Temperature Conversion
TEMPERATURE
DECREASING
TEMPERATURE ( C)
frame
6
RIGHT-SHIFTS NEEDED
. Temperature conver-
TEMPERATURE
INCREASING
8
NUMBER OF
10
0
1
2
3
4
12