Logic electrical characteristics, 0 functional description, Lm83 – Rainbow Electronics LM83 User Manual

Page 8

Logic Electrical Characteristics

(Continued)

Note 6: Typicals are at T

= 25˚C and represent most likely parametric norm.

Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 8: The Temperature Error will vary less than

1.0 ˚C for a variation in V

of 3 V to 3.6 V from the nominal of 3.3 V.

Note 9: Quiescent current will not increase substantially with an active SMBus.

Note 10: This specification is provided only to indicate how often temperature data is updated. The LM83 can be read at any time without regard to conversion state
(and will yield last conversion result).

Note 11: Default values set at power up.

Note 12: Holding the SMBData and/or SMBCLK lines Low for a time interval greater than t

TIMEOUT

will cause the LM83 to reset SMBData and SMBCLK to the IDLE

state of an SMBus communication (SMBCLK and SMBData set High).

1.0 Functional Description

The LM83 temperature sensor incorporates a band-gap type
temperature sensor using a Local or three Remote diodes
and an 8-bit ADC (Delta-Sigma Analog-to-Digital Converter).
The LM83 is compatible with the serial SMBus and I

C two

wire interfaces. Digital comparators compare Local (LT) and
Remote (D1RT, D2RT and D3RT) temperature readings to
user-programmable

setpoints

(LHS,

D1RHS,

D2RHS,

D3RHS and TCS). Activation of the INT output indicates that
a comparison is greater than the limit preset in a HIGH reg-
ister. The T_CRIT setpoint (TCS) interacts with all the tem-
perature readings. Activation of the T_CRIT_A output indi-
cates that any or all of the temperature readings have
exceed the T_CRIT setpoint.

1.1 CONVERSION SEQUENCE

The LM83 converts its own temperature as well as 3 remote
diode temperatures in the following sequence:

Local Temperature (LT)

Remote Diode 2 (D2RT)

Remote Diode 1 (D1RT)

Remote Diode 3 (D3RT)

This round robin sequence takes approximately 480 ms to
complete as each temperature is digitized in approximately
120 ms.

1.2 INT OUTPUT and T_HIGH LIMITS

Each temperature reading (LT, D1RT, D2RT, and D3RT) is
associated with a T_HIGH setpoint register (LHS, D1RHS,
D2RHS, D3RHS). At the end of a temperature reading a digi-
tal comparison determines whether that reading has exceed
its HIGH setpoint. If the temperature reading is greater than
the HIGH setpoint, a bit is set in one of the Status Registers,
to indicate which temperature reading, and the INT output is
activated.

Local and remote temperature diodes are sampled in se-
quence by the A/D converter. The INT output and the Status

DS101058-5

FIGURE 2. Temperature-to-Digital Transfer Function (Non-linear scale for clarity)

DS101058-24

FIGURE 3. Printed Circuit Board Used for Thermal Resistance Specifications

LM83