MAX7501 Maxim, MAX7501 Datasheet - Page 10

• Manufacturer Part Number: MAX7501
• Description: Digital Temperature Sensors and Thermal Watchdog with Bus Lockup Protection
• Manufacturer: Maxim

Set bit D0 in the configuration register to 1 to place the
MAX7500/MAX7501/MAX7502 in shutdown mode and
reduce supply current to 3µA.
The MAX7500/MAX7501/MAX7502 power up to a
known state, as indicated in
settings are summarized below:
• Comparator mode
• T
• T
• OS active low
• Pointer = 00
The MAX7500/MAX7501/MAX7502s’ pointer register
selects between four data registers. See
power-up, the pointer is set to read the temperature
register at address 00. The pointer register latches the
last location to which it was set. All registers are read
and write, except the temperature register, which is
read only.
Write to the configuration register by writing an address
byte, a data pointer byte, and a data byte. If 2 data
bytes are written, the second data byte overrides the
first. If more than 2 data bytes are written, only the first
2 bytes are recognized while the remaining bytes are
ignored. The T
address byte and 1 pointer byte and 2 data bytes. If
only 1 data byte is written, it is saved in bits D15–D8 of
the respective register. If more than 2 data bytes are
written, only the first 2 bytes are recognized while the
remaining bytes are ignored.
Read from the MAX7500/MAX7501/MAX7502 in one of
two ways. If the location latched in the pointer register
is set from the previous read, the new read consists of
an address byte, followed by retrieving the correspond-
ing number of data bytes. If the pointer register needs
to be set to a new address, perform a read operation
by writing an address byte, pointer byte, repeat start,
and another address byte.
An inadvertent 8-bit read from a 16-bit register, with the
D7 bit low, can cause the MAX7500/MAX7501/
MAX7502 to stop in a state where the SDA line is held
low. Ordinarily, this would prevent any further bus com-
munication until the master sends nine additional clock
cycles or SDA goes high. At that time, a stop condition
Digital Temperature Sensors and Thermal
Watchdog with Bus Lockup Protection
10
OS
HYST
______________________________________________________________________________________
= +80 C
= +75 C
OS
Power-Up and Power-Down
and T
HYST
Table
Internal Registers
registers require 1
2. Some of these
Shutdown
Figure
5. At
resets the device. With the MAX7500/MAX7501/
MAX7502, if the additional clock cycles are not gener-
ated by the master, the bus resets and unlocks after
the bus timeout period has elapsed.
The MAX7501/MAX7502 can be reset by pulsing
RESET low.
Communication errors sometimes occur due to noise
pickup on the bus. In the worst case, such errors can
cause the slave device to hold the data line low, there-
by preventing other devices from communicating over
the bus. The MAX7500/MAX7501/MAX7502s’ internal
bus timeout circuit resets the bus and releases the data
line if the line is low for more than 250ms. When the bus
timeout is active, the minimum serial clock frequency is
limited to 6Hz.
The RESET input on the MAX7501/MAX7502 provides a
way to reset the I
their initial POR values. To reset, apply a low pulse with
a duration of at least 1µs to the RESET input.
Figure 5. Block Diagram
A2/RESET
SCL
A0
A1
SDA
POINTER = 0000 0000
POINTER = 0000 0011
TEMPERATURE
T
(READ/WRITE)
(READ ONLY)
OS
SET POINT
2
C bus and all the internal registers to
DATA
+V
FOR COMMUNICATION)
S
(SELECTS REGISTER
POINTER REGISTER
INTERFACE
SMBus
BLOCK
GND
REGISTER SELECT
ADDRESS
POINTER = 0000 0001
POINTER = 0000 0010
CONFIGURATION
T
HYST
(READ/WRITE)
(READ/WRITE)
MAX7500
MAX7501
MAX7502
SET POINT
Bus Timeout
RESET
OS