MAX1358B Maxim Integrated Products, MAX1358B Datasheet - Page 32

• Manufacturer Part Number: MAX1358B
• Description: Data-Acquisition System
• Manufacturer: Maxim Integrated Products

DataSheet.in
Program each UPIO1–UPIO4 as one of the following:
• General-purpose input
• Power-mode control
• Analog switch (SPST) and SPDT control input
• ADC data-ready output
• General-purpose output
• PWM output
• Alarm output
• SPI pass-through
An internal transistor or a remote transistor (or diode) is
used with the ADC and a programmable current source
to measure the ambient temperature. Depending on the
method, either two or four currents are passed through
the PN junction. The voltage across the PN junction is
measured at each current. For each current, the voltage
across a series resistor is also measured. Measuring the
voltage across the resistor allows the user to determine
the precise current ratios. A microcontroller can then
use the diode equation to calculate the temperature.
The four-current method eliminates errors caused by
parasitic resistance in series with the diode, which
increases the apparent voltage across the PN junction.
When measuring temperature using the internal transis-
tor for a sensor, the two-current method is usually ade-
quate although the four-current method can also be
used. Refer to Application Note 4296: Measuring
Temperature with the MAX1358 Data Acquisition System
for details on the measurement procedure.
16-Bit, Data-Acquisition System with ADC, DACs,
UPIOs, RTC, Voltage Monitors, and Temp Sensor
Figure 12. High-Frequency Clock and FLL Block Diagram
32
M32K
______________________________________________________________________________________
Internal and External (Remote)
FLLE
FREQUENCY
COMPARE
Temperature Sensors
ERROR
FREQ
32.768kHz
FREQUENCY
INTEGRATOR
TUNE<8:0>
CONTROLLED
OSCILLATOR
DIGITALLY
HFCE
Figure 13. Temperature-Sensor Measurement Block Diagram
AIN1
AIN2
CKSEL2
0
1
MUX
2:1
4.9152MHz HF OSCILLATOR AND FLL
IMUX<1:0>
IVAL<1:0>
CKSEL<1:0>
4.9152MHz
1, 2, 4, 8
DIVIDER
PROGRAMMABLE CURRENT SOURCE
TEMP SENSOR
CURRENT
SOURCE
DEMUX
CLKE
1:3
CRDY
HFCLK
AIN1
AIN2
TEMP+
TEMP-
CLK