MAX1617 데이터 시트보기 (PDF) - Maxim Integrated

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MAX1617

Remote/Local Temperature Sensor with SMBus Serial Interface

Maxim Integrated 

MAX1617

Remote/Local Temperature Sensor

with SMBus Serial Interface

Pin Description

PIN

1, 5, 9,

13, 16

NAME

N.C.

2

VCC

3

DXP

4

DXN

6

ADD1

7, 8

GND

10

ADD0

11

ALERT

12

SMBDATA

14

SMBCLK

15

STBY

FUNCTION

No Connection. Not internally connected. May be used for PCB trace routing.

Supply Voltage Input, 3V to 5.5V. Bypass to GND with a 0.1μF capacitor. A 200Ω series resistor is

recommended but not required for additional noise filtering.

Combined Current Source and A/D Positive Input for remote-diode channel. Do not leave DXP

unconnected; tie DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and

DXN for noise filtering.

Combined Current Sink and A/D Negative Input. DXN is normally biased to a diode voltage above

ground.

SMBus Address Select pin (Table 8). ADD0 and ADD1 are sampled upon power-up. Excess capacitance

(>50pF) at the address pins when unconnected may cause address-recognition problems.

Ground

SMBus Slave Address Select pin

SMBus Alert (interrupt) Output, open drain

SMBus Serial-Data Input/Output, open drain

SMBus Serial-Clock Input

Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode.

Low = standby mode, high = operate mode.

Detailed Description

The MAX1617 is a temperature sensor designed to work

in conjunction with an external microcontroller (μC) or

other intelligence in thermostatic, process-control, or

monitoring applications. The μC is typically a power-man-

agement or keyboard controller, generating SMBus serial

commands by “bit-banging” general-purpose input-output

(GPIO) pins or via a dedicated SMBus interface block.

Essentially an 8-bit serial analog-to-digital converter

(ADC) with a sophisticated front end, the MAX1617

contains a switched current source, a multiplexer, an

ADC, an SMBus interface, and associated control logic

(Figure 1). Temperature data from the ADC is loaded into

two data registers, where it is automatically compared

with data previously stored in four over/under-tempera-

ture alarm registers.

ADC and Multiplexer

The ADC is an averaging type that integrates over a

60ms period (each channel, typical), with excellent

noise rejection.

The multiplexer automatically steers bias currents through

the remote and local diodes, measures their forward volt-

ages, and computes their temperatures. Both channels

are automatically converted once the conversion process

has started, either in free-running or single-shot mode.

If one of the two channels is not used, the device still

performs both measurements, and the user can simply

ignore the results of the unused channel. If the remote

diode channel is unused, tie DXP to DXN rather than leav-

ing the pins open.

The DXN input is biased at 0.65V typical above ground

by an internal diode to set up the analog-to-digital (A/D)

inputs for a differential measurement. The typical DXP–

DXN differential input voltage range is 0.25V to 0.95V.

To ensure proper operation over full temperature range,

ensure VDXP ≤ (0.78 x VCC - 1.1) volts.

Excess resistance in series with the remote diode causes

about +1/2°C error per ohm. Likewise, 200μV of offset

voltage forced on DXP–DXN causes about 1°C error.

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