MAX11359AETL Maxim Integrated, MAX11359AETL Datasheet - Page 31

• Manufacturer Part Number: MAX11359AETL
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX11359AETL

• Number Of Channels: 10
• Architecture: Sigma-Delta
• Conversion Rate: 10 SPs to 512 SPs
• Resolution: 16 bit
• Input Type: Differential
• Interface Type: 4-Wire Serial, Microwire, QSPI, SPI
• Operating Supply Voltage: 1.8 V to 3.6 V
• Maximum Power Dissipation: 2051.3 mW
• Number Of Converters: 1
• Voltage Reference: 1.251 V 1.996 V, 2.422 V

For the two-current method, currents I
passed through a p-n junction. This requires two V
measurements. Temperature measurements can be
performed using I
where k is Boltzman’s constant and q is the absolute
value of the charge on electron. A four-measurement
procedure is adopted to improve accuracy by precisely
measuring the ratio of I
1) Current I
2) For the same current, the voltage across the diode
3) Repeat steps 1 and 2 with I
Since only four integer numbers are accessible from the
ADC conversions at a certain voltage reference, the previ-
ous equation can be represented in the following manner:
where N
ment results in integer format and V
voltage used in the ADC measurements.
The four-current method is used to account for the
diode series resistance and trace resistance. The four
currents are defined as follows; I
the currents are selected so (M
effect of the series resistance is eliminated from the
temperature measurements. For the currents I
and I
M
and I
current method, two measurements per current are
Maxim Integrated
UPIOs, RTC, Voltage Monitors, and Temp Sensor
2
resistor R, and the voltage across the diode is mea-
sured as V
and R is measured as V
I
2
= 2. This results in the currents I
16-Bit Data-Acquisition System with ADC, DAC,
2
4
is typically 60µA (see Table 21).
= 60µA, the factors are selected as M
= M
T
V1
MEAS
, N
2
1
I
2
is driven through the diode and the series
BE1
V2
= 120µA (typ). As in the case of the two-
T
=
MEAS
, N
.
1
nk
and I
VBE1
q N
(
ln
1
=
VBE
⎛
⎜
⎝
, and N
2
and I
N
.
N
q V
1
V
(
V
2
.
2
nk
1
BE
−
2
−
−
:
N
2
N
N
1
2
ln
. I
VBE2
VBE
1
VBE
VBE
Four-Current Method
−
Two-Current Method
⎛
⎜
⎝
- 1)I
, I
1
I
I
V
2
1
2
REF
is typically 4µA and
1
BE
1
2
⎞
⎟
⎠
, M
)
1
are the measure-
3
⎞
⎟
⎠
1
= (M
)
×
1
is the reference
= M
I
1
V
1
2
, and M
REF
16
2
and I
1
1
I
- 1)I
1
= 16 and
1
= 64µA
= 4µA
2
2
2
, the
I
2
are
BE
. If
used to improve accuracy by precisely measuring the
values of the currents.
1) Current I
2) For the same current, the voltage across the diode and
3) Repeat steps 1 and 2 with I
The measured temperature is defined as follows:
where V
For an external temperature sensor, either the two-cur-
rent or four-current method can be used. Connect an
external diode (such as 2N3904 or 2N3906) between
pins AIN1 and AGND (or AIN2 and AGND). Connect a
sense resistor R between AIN1 and AIN2. Maximize R
so the IR drop plus V
I
or (AVDD - 400mV). The same procedure as the inter-
nal temperature sensor can be used for the external
temperature sensor, by routing the currents to AIN1 (or
AIN2) (see Table 20).
For the two-current method, if the external diode’s
series resistance (R
measurement can be corrected as shown below:
To account for various error sources during the temper-
ature measurement, the internal temperature sensor is
calibrated at the factory. The calibrated temperature
equation is:
MAX
T
T
ACTUAL
MEAS
resistor R, and the voltage is measured across the
diode using the ADC as NVBE1.
the series resistor is measured by the ADC as NV1.
)+V
REF
=
BE
=
T
q N
M
M
MEAS
] is the smaller of the ADC reference voltage
(
1
1
2
is the reference voltage used and:
VBE
is driven through the diode and the series
=
−
⎛
⎜
⎝
⎛
⎜
⎜
⎜
⎜
⎝
N
3
N
q N
V
(
−
V
3
1
V
N
S
2
−
−
Temperature-Sensor Calibration
VBE
) is known, then the temperature
nkIn
−
N
N
nkIn
N
VBE
VBE
External Temperature Sensor
BE
VBE
1
⎛
⎜
⎝
MAX11359A
)
N
N
−
⎛
⎜
⎝
V
1
2
3
V
of the p-n junction [(R x
M
2
)
q N
M
1
⎞
⎟
⎠
−
−
−
(
2
1
2
⎛
⎜
⎝
q N
N
N
, I
N
N
(
⎞
⎟
⎠
VBE
VBE
VBE
3
V
V
V
, and I
1
4
2
1
2
−
4
−
−
⎞
⎟
⎠
N
−
N
N
VBE
N
VBE
VBE
4
VBE
1
)
.
×
2
4
V
2
⎞
⎟
⎠
2
REF
16
)
×
×
V
2
R
REF
R
16
S
⎞
⎟
⎟
⎟
⎟
⎠
31