MAXIM DS7505 User Manual

General Description

The DS7505 low-voltage (1.7V to 3.7V) digital thermometer and thermostat provides 9-, 10-, 11-, or 12-bit digital temperature readings over a -55°C to +125°C range with ±0.5°C accuracy over a -0°C to +70°C range. A 9-bit resolution mode is software compatible with the LM75. Communication with the DS7505 is achieved through a simple 2-wire serial interface. Three address pins allow up to eight DS7505 devices to operate on the same 2-wire bus, which greatly simplifies distributed temperature-sensing applications.

The DS7505 thermostat has a dedicated open-drain output (O.S.) and programmable fault tolerance, which allows the user to define the number of consecutive error conditions that must occur before O.S. is activated. There are two thermostatic operating modes that control thermostat operation based on user-defined trip points (T

and T

HYST

) that are stored in EEPROM registers.

Applications

Networking Equipment

Cellular Base Stations

Office Equipment

Medical Equipment

Any Thermally Sensitive System

Features

♦ Operating Range from 1.7V to 3.7V

♦ Temperature Measurements Require No External

Components

♦ Measures Temperatures from -55°C to +125°C

(-67°F to +257°F)

♦ ±0.5°C Accuracy Over a 0°C to +70°C Range

♦ Thermometer Resolution is User-Configurable

from 9 (Default) to 12 Bits (0.5°C to 0.0625°C Resolution)

♦ 9-Bit Conversion Time is 25ms (max)

♦ Thermostatic Settings are User-Definable and

Nonvolatile (NV)

♦ Stand-Alone Thermostat Capability

♦ Data Read/Write Occurs Through a 2-Wire Serial

Interface (SDA and SCL Pins)

♦ Data Lines Filtered Internally for Noise Immunity

(50ns Deglitch)

♦ Optional Bus Timeout Feature Prevents Lockup

Problems on 2-Wire Interface

♦ Multidrop Capability Simplifies Distributed

Temperature-Sensing Applications

♦ Pin/Software Compatible with the LM75

♦ Available in 8-Pin SO and µMAX

Packages

DS7505

Digital Thermometer and Thermostat

________________________________________________________________

Maxim Integrated Products

Pin Configurations

Ordering Information

Rev 1; 3/08

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Denotes a lead(Pb)-free/RoHS-compliant package.

T&R = Tape and reel.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

Commands are capitalized for clarity.

TOP VIEW

1 8 VDDSDA

27A0SCL

1 8 VDDSDA

27A0SCL

DS7505

MAX

A1O.S. 3 6

A2GND

A1O.S. 3 6

A2GND 4 5

PART TEMP RANGE PIN-PACKAGE

DS7505S+ -55°C to +125°C 8 SO (150 mils)

DS7505S+T&R -55°C to +125°C

DS7505U+ -55°C to +125°C 8 μMAX

DS7505U+T&R -55°C to +125°C

8 SO (150 mils), 2500-Piece T&R

8 μMAX, 3000-Piece T&R

DS7505

Digital Thermometer and Thermostat

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

DC ELECTRICAL CHARACTERISTICS

(1.7V ≤ VDD≤ 3.7V, TA= -55°C to +125°C, unless otherwise noted.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Voltage Range on VDD Relative to Ground ..........-0.3V to +4.0V

Voltage Range on Any Other Pin

Relative to Ground.............................................-0.3V to +6.0V

Operating Temperature Range .........................-55°C to +125°C

Storage Temperature Range .............................-55°C to +125°C

Soldering Temperature...........................Refer to the IPC/JEDEC

J-STD-020 Specification.

AC ELECTRICAL CHARACTERISTICS

(1.7V ≤ VDD≤ 3.7V, TA= -55°C to +125°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

Supply Voltage VDD 1.7 3.7 V

Input Voltage Range (SDA, SCL, O.S., A0, A1, A2)

Thermometer Error (Note 2, 3)

Input Logic-High VIH (Note 1) 0.7 × VDD V

Input Logic-Low VIL (Note 1) 0.3 × VDD V

SDA Output Logic-Low Voltage V

O.S. Saturation Voltage V

Input Current Each I/O pin 0.4V < V

I/O Capacitance C

Standby Current I

Active Current (Notes 4, 5, 6)

(Note 1) -0.3 +5.5 V

ERR

OL1

OL2

I/O

DD1

0°C to +70°C ± 0.5

-55°C to +125°C ± 2.0

6mA sink current (Note 1) 0 0.6 V

4mA sink current (Notes 1, 2) 0.8 V

I/O

10 pF

(Notes 4, 5, 6) 2 μA

Active temp convers ions 750

Communication only 100

Copy only 500

< 0.9 x VDD -10 +10 μA

°C

μA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Resolution 9 12 Bits

9-bit conversions 25

Temperature Conversion Time t

SCL Frequency f

EEPROM Copy Tim e tWR -40°C to +85°C 10 ms

EEPROM Copy Endurance N

CONVT

SCL

EEWR

10-bit con version s 50

11-bit con version s 100

12-bit con version s 200

400 kH z

-40°C  TA +85°C (Note 7) 10k 20k

TA= +25°C (Note 7) 40k 80k

Cycles

DS7505

Digital Thermometer and Thermostat

_______________________________________________________________________________________ 3

Note 1: All voltages are referenced to ground. Note 2: Internal heating caused by O.S. loading causes the DS7505 to read approximately 0.5°C higher if O.S. is sinking the

max-rated current.

Note 3: Specified in 12-bit conversion mode. Quantization error must be considered when converting in lower resolutions. Note 4: I

specified with O.S. pin open.

Note 5: I

specified with VDDat 3.0V and SDA, SCL = 3.0V, TA= -55°C to +85°C.

Note 6: I

specified with A0, A1, A2 = 0V or VDD.

Note 7: V

must be > 2.0V.

Note 8: E

Copy occurs at +25°C.

Note 9: See the timing diagram (Figure 1). All timing is referenced to 0.9 x V

and 0.1 x VDD.

Note 10: After this period, the first clock pulse is generated. Note 11: The DS7505 provides an internal hold time of at least 75ns on the SDA signal to bridge the undefined region of SCL’s

falling edge.

Note 12: For example, if C

= 300pF, then t

R(MIN)

= t

F(MIN)

= 50ns.

Note 13: This timeout applies only when the DS7505 is holding SDA low. Other devices can hold SDA low indefinitely and the

DS7505 does not reset.

AC ELECTRICAL CHARACTERISTICS (continued)

(1.7V ≤ VDD≤ 3.7V, TA= -55°C to +125°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

EEPROM Data Retention t

Bus Free Time Between a STOP and START Condition

START and Repeated START Hold Time from Falling SCL

Low Period of SCL t

High Period of SCL t

Repeated START Condition Setup Time to R ising SCL

Data-Out Hold Time from Falling SCL

Data-In Setup Time to Ri sing

Rise T ime of SDA and SCL (Receive)

Fall Time of SDA and SCL (Receive)

Spike Suppression Filter Time (Deglitch Filter)

STOP Setup Time to Rising SCL t

Capacitive Load for Each Bus Line

Input Capacitance CI 5 pF

Serial Interface Reset Time t

-40°C to +125°C (Note 8) 10 Years

EEDR

(Note 9) 1.3 μs

BUF

HD: STA

LOW

HIGH

SU:STA

HD:DAT

SU:DAT

SU:STO

TIMEOUT

(Notes 9, 10)

(Note 9) 1.3 μs

(Note 9) 0.6 μs

(Note 9) 600 ns

(Notes 9, 11) 0 0.9 μs

(Note 9) 100 ns

(Notes 9, 12)

0 50 ns

(Note 9) 600 ns

400 pF

SDA time low (Note 13) 75 325 m s

600

20 +

0.1C

20 +

0.1C

300

300 ns

DS7505

Digital Thermometer and Thermostat

4 _______________________________________________________________________________________

Pin Description

Figure 1. Timing Diagram

Figure 2. Block Diagram

PIN NAME FUNCTION

1 SDA Data Input/Output. For 2-wire serial commun ication port. Open drain.

2 SCL Clock Input. For 2-wire serial communication port.

3 O.S. Thermo stat Output. Open drain.

4 GND Ground

5 A2 Address Input

6 A1 Address Input

7 A0 Address Input

8 VDD Supply Voltage. +1.7V to +3.7V supply pin.

SDA

LOW

SU:DAT

HD:STA

SPtR

BUF

SCL

VDD

SCL

SDA

A0 A1 A2

GND

HD:STA

HD:DAT

PRECISION REFERENCE

ADDRESS

AND

I/O CONTROL

DS7505

SU:STA

OVERSAMPLING

MODULATOR

CONFIGURATION

TEMPERATURE

TOS AND T

HYST

REGISTERS

SU:STO

SR P S

DIGITAL

DECIMATOR

O.S.

THERMOSTAT

COMPARATOR

DS7505

Digital Thermometer and Thermostat

_______________________________________________________________________________________ 5

Figure 3. Temperature, TOS, and T

HYST

Table 1. 12-Bit Resolution Temperature/Data Relationship

Operation⎯Measuring

Temperature

The DS7505 measures temperature using a bandgap temperature-sensing architecture. An on-board deltasigma analog-to-digital converter (ADC) converts the measured temperature to a digital value that is calibrated in degrees Celsius; for Fahrenheit applications a lookup table or conversion routine must be used. The DS7505 is factory-calibrated and requires no external components to measure temperature.

The DS7505 can be configured to power up either automatically converting temperature or in a low-power standby state. The preferred power-up mode can be set using the SD bit in the configuration register as explained in the

Configuration Register

section. The resolution of the digital output data is user-configurable to 9, 10, 11, or 12 bits, corresponding to temperature increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively. The factory default resolution at power-up is 9 bits (R1 = 0, R0 = 0), however this can be programmed to 10, 11, or 12 bits using the R0 and R1 bits in the configuration register as explained in the

Configuration Register

section. Note that the conver-

sion time doubles for each additional bit of resolution.

After each temperature measurement and analog-todigital (A/D) conversion, the DS7505 stores the temperature as a 16-bit two’s complement number in the 2-byte temperature register (see Figure 3). The sign bit (S) indicates if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. The most recently converted digital measurement can be read from the temperature register at any time. Since temperature conversions are performed in the background, reading the temperature register does not affect the operation in progress.

Bits 3 through 0 of the temperature register are hardwired to 0. When the DS7505 is configured for 12-bit resolution, the 12 MSBs (bits 15 through 4) of the temperature register contain temperature data. For 11-bit resolution, the 11 MSBs (bits 15 through 5) of the temperature register contain data, and bit 4 reads out as 0. Likewise, for 10-bit resolution, the 10 MSBs (bits 15 through 6) contain data, and for 9-bit the 9 MSBs (bits 15 through 7) contain data and all unused LSBs contains 0s. Table 1 gives examples of 12-bit resolution digital output data and the corresponding temperatures.

MS Byte S 2

LS Byte 2-1 2

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

-2

-3

-4

0 0 0 0

TEMPERATURE (°C)

+125 0111 1101 0000 0000 7D00

+25.0625 0001 1001 0001 0000 1910

+10.125 0000 1010 0010 0000 0A20

+0.5 0000 0000 1000 0000 0080

0 0000 0000 0000 0000 0000

-0.5 1111 1111 1000 0000 FF80

-10.125 1111 0101 1110 0000 F5E0

-25.0625 1110 0110 1111 0000 E6F0

-55 1100 1001 0000 0000 C900

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

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