DS1852 datasheet(6/25 Pages) DALLAS

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DS1852

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bits. This step has now adjusted the LSB of the lower 12 bits so that the best possible trim is

acquired with the lower 12 bits.

If too high a value is used in the four bits, then the resolution of the 12 bits is too high and absolute

accuracy is sacrificed. If too low a value is used in the four bits, then the resolution of the 12 bits is too

small, so a maximum reading is not possible and a large gain error is present through the entire range.

Example code can be found near the end of this data sheet.

POWER-ON LOGIC

VCC is compared to an internal reference voltage, and if it is below VCC minimum, all internal logic and

outputs are held in their reset state. When VCC rises above VCC minimum, the system reset is released.

The DS1852 will not begin monitoring operations until VCC has risen above the analog minimum

voltage. However, communication on the 2-wire bus can occur at a VCC level lower than the analog

minimum voltage. This allows access to the power-on logic bit located in Table 00h, address 6Eh, bit 0.

The analog minimum voltage is less than 2.7V but greater than the digital minimum voltage. Above the

analog minimum voltage, the DS1852 will begin to function in a predictable manner but will not satisfy

specifications until VCC is above 2.7V.

TEMPERATURE-DEPENDENT FAST ALARM COMPARATORS

The DS1852 has a three-input muxing fast alarm comparator with a response time of less than 10µs for

each input. This provides a coarse but fast approximation of whether analog inputs Bin, Pin, and Rin are

above their temperature-dependent value. Each comparator has an 8-bit max value set in Table 03h,

address D8h to E7h. The trip point range is adjustable from 10mV to 2.5V. Each LSB is approximately

10mV. The outputs of these comparators are readable in Table 00h (alarm bytes 1 and 0) and may be

overwritten if their corresponding fast alarm override bit is set in Table 03h EEPROM.

The Bin alarm can be set to eight unique temperature-dependent trip values, which allows the user to set

trip points for different temperature ranges. The Pin/Rin fast alarms act similarly, but can only be set to

four unique temperature-dependent values. For more information, refer to Table 03h.

HIGH-RESOLUTION ALARM COMPARATORS

There are 10 alarm comparators for the five analog channels. There is a 'high alarm' comparator whose

output is active if the analog signal is above its threshold and a 'low alarm' comparator whose output is

active if the analog signal is below its threshold. These comparators have a 2-byte set point in the same

format as the analog converter data in Table 03h. The outputs of these comparators are readable in Table

00h (70h) and may be overwritten if their corresponding alarm override bit is set in Table 03h

EEPROM.

WARNING COMPARATORS

The 10 warning comparators function the same way as the alarm comparators, but can be set to trip at

different levels. Typically, they would be set to trip prior to the alarm comparators. The set points are in

Table 03h and the outputs can be read from Table 00h.

DS1852 Datenblatt(PDF) 6 Page - Dallas Semiconductor