DS2422 Maxim, DS2422 Datasheet - Page 6

• Manufacturer Part Number: DS2422
• Description: The DS2422 temperature/data logger combines the core functions of a fully featured data logger in a single chip
• Manufacturer: Maxim

PIN DESCRIPTION
DESCRIPTION
The DS2422 temperature/data logger combines the core functions of a fully featured data logger in a single chip. It
includes a temperature sensor, RTC, memory, 1-Wire interface, and serial interface for an analog-to-digital
converter (ADC) as well as control circuitry for a charge pump. The ADC and the charge pump are peripherals that
can be added to build application-specific data loggers. Without external ADC, the DS2422 functions as a
temperature logger only. The DS2422 measures the temperature and/or reads the ADC at a user-defined rate. A
total of 8192 8-bit readings or 4096 16-bit readings taken at equidistant intervals ranging from 1 second to 273
hours can be stored. In addition to this, there are 512 bytes of SRAM for storing application specific information and
64 bytes for calibration data. A mission to collect data can be programmed to begin immediately, after a user-
defined delay, or after a temperature alarm. Access to the memory and control functions can be password-
protected. The DS2422 is configured and communicates with a host computing device through the serial 1-Wire
protocol, which requires only a single data lead and a ground return. Every DS2422 is factory-lasered with a
guaranteed unique 64-bit registration number that allows for absolute traceability. The extremely low energy con-
sumption in conjunction with its high level of programmability makes the DS2422 the ideal choice for low-cost data
loggers that can take millions of measurements from the energy of a single 3V button cell.
APPLICATION
The DS2422 allows the design of data loggers or monitors with a minimum number of components. The simple
circuit of Figure 1 can monitor body or room temperature with 0.0625°C resolution. For very high temperature-
monitoring applications, a thermocouple can be connected to the analog-to-digital converter (ADC) through a pre-
amplifier, as shown in Figure 2. The internal temperature sensor of the DS2422 keeps track of the reference
temperature, which is needed to accurately convert the voltage reading of the thermocouple into the actual
temperature of the monitored object. A less obvious application of the DS2422 is inside of major equipment.
Besides the temperature inside the chassis, the serial interface can monitor up to 16 digital signals, which are
parallel-clocked into an external shift register by CNVST and then shifted into the DS2422 through the SDATA pin
9 pins
PIN
10
11
12
13
14
16
21
22
23
24
1
2
3
4
9
TEST_SPLY
PUMP_ONZ
TEST_CG
TEST_RX
ALARM
SDATA
CNVST
NAME
AGND
SCLK
GND
V
V
NC
X1
X2
IO
PAD
BAT
Operating voltage of the serial interface pads CNVST, SCLK, SDATA. Used for
level translation from the V
Connect to V
Serial clock signal for serial interface. May connect directly to the corresponding
MAX1086 pin. The idle state for the pin is low.
Serial data pin for the serial interface. May connect directly to the DOUT pin of
MAX1086. The pin includes a weak pulldown and therefore has an idle state of low.
Conversion Start control signal for the MAX1086. The idle state for the pin is low.
Analog ground. Ground reference for external ADC and charge pump.
First of two crystal pins for the real time clock crystal. A standard 6pF 32KHz crystal
is used. The accuracy of the device's real time clock is largely dependent on the
temperature characteristics of the crystal. Trace length from the device to the crystal
should be minimized to reduce their capacitive effect.
Logic open-drain output with 215 maximum on-resistance, operating range 0V to
5.25V. Power-on default is OFF.
Second of two crystal pins for the real time clock crystal.
1-Wire communication line, data input and output. This pin also charges the internal
parasitic power cap that allows the 1-Wire front end of the device to run without V
supply.
Common ground supply for the device and V
Connect to GND (test pin)
Connect to GND (test pin)
Signal to control an external charge-pump. The signal polarity is designed to fit to
the MAX619 charge pump/regulator.
3V power supply for the device, typically a battery. This pin supplies power to all
parts of the device except for the 1-Wire front end.
Do not connect (test pin)
Not connected
BAT
if the serial interface is not used.
6 of 49
BAT
-powered internal logic to the 5V-powered ADC.
FUNCTION
BAT
.
BAT