Datasheet

Detailed Description
The MAX6575L/H low-cost, low-current (150μA typ)
temperature sensor is ideal for interfacing with microcon
trollers or microprocessors. The MAX6575L/H is a mono-
stable, externally triggered temperature sensor that uses
a Temp→Delay conversion to communicate with a μP
over a single I/O line. Time-select pins (TS1, TS0) per-
mit the internal temperature-controlled oscillator (TCO)
to be scaled by four preset timeout multipliers, allowing
eight separate temperature sensors to share one I/O line.
Different sensors on the same I/O line will use different
timeout multipliers to avoid overlapping signals.
Operating the MAX6575L/H
Figure 1 illustrates the timing for the MAX6575L/H. When
the device is powered up, it assumes a ready state where
it awaits an external trigger at the I/O pin. The I/O pin
of the MAX6575L/H has an open-drain output structure
that requires a pullup resistor to maintain the proper logic
levels. Once the I/O pin is pulled low and then released,
control of the I/O pin is transferred to the MAX6575L/H.
The temperature conversion begins on the falling edge
of the externally triggered pulse. The I/O line is pulled
low at a later time. That time is determined by the device
temperature and the Time Select pins (TS1, TS0). The
I/O line remains low for 5Tμs, where T is the temperature
in degrees Kelvin. The temperature of the device is rep-
resented by the edgeto-edge delay of the externally trig-
gered pulse and the falling edge of the subsequent pulse
originating from the device. The device can be manually
reset by pulling the I/O line low for more than t
RESET
(16ms max). The device will automatically reset after a
maximum delay of 520ms, at which point it will again be
in a ready state awaiting a start pulse.
Definition of Terms:
t
RESET
: Time I/O must be externally pulled low to guar-
antee the MAX6575L/H is in a ready state await-
ing external trigger. (Part will assume a ready
state after 520ms without a reset pulse.)
t
SETUP
: Time I/O must be high prior to a start pulse.
t
START
: Trigger pulse which starts the on-chip timing
sequence on its falling edge.
t
Dx
: Timing delay between the falling edge of the
start pulse and the falling edge initiated by
CHIP#x.
t
Lx:
I/O pulse low time (5Tμs).
t
READY
: Time after falling edge of start pulse when the
MAX6575L/H will reset itself and await the next
external trigger.
The temperature, in degrees Celsius, may be calculated
as follows:
T(°C) = [t
Dx(μs)
/ timeout multiplier(μs/°K)] - 273.15°K
Figure 1. Timing Diagram
Table 1. Time-Select Pin Configuration
TIME-SELECT PINS
TIMEOUT MULTIPLIERS
(μs/°K)
TS1 TS0
MAX6575L MAX6575H
GND GND 5 160
GND V
DD
20 320
V
DD
GND 40 480
V
DD
V
DD
80 640
t
RESET
APPLIED START
PULSE
CHIP# 1
RESPONSE
CHIP# 2
RESPONSE
CHIP# 3
RESPONSE
CHIP# 4
RESPONSE
t
D1
t
L1
t
L2
t
D2
t
D3
t
L3
t
D4
t
L4
t
READY
t
SETUP
t
START
MAX6575L/H SOT Temperature Sensor with
Multidrop Single-Wire Digital Interface
www.maximintegrated.com
Maxim Integrated │ 4