DS1780E Maxim Integrated Products, DS1780E Datasheet - Page 6

• Manufacturer Part Number: DS1780E
• Description: IC CPU PERIPHERAL MON 24-TSSOP
• Manufacturer: Maxim Integrated Products

Specifications of DS1780E

• Function: Thermal Monitor, CPU Peripherals
• Topology: ADC (Sigma Delta), Comparator, Fan Speed Control, Register Bank
• Sensor Type: Internal
• Sensing Temperature: -40°C ~ 125°C
• Output Type: I²C™/SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 2.8 V ~ 5.75 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Full Temp Accuracy: +/- 12 %
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 8 bit
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DS1780
2-WIRE SERIAL COMMUNICATION WITH THE DS1780 Figure 2
OPERATION - Power-on
Applying power to the DS1780 causes a reset of several of the registers. Power-on conditions of the
registers are shown in Table 2 above. Some registers have indeterminate power-on values, such as the
Limit and RAM registers of the Value RAM page, and these are not shown in the table. Upon power-up
the ADC is inactive. Writing Limits into the Value RAM should usually be the first action performed
after power up. The
pin is bi-directional. It forces RESET at power-on, but can also be pulled low to
RST
force RESET internally.
OPERATION - Resets
The DS1780 features four distinct resetting functions. Each one has a different effect on register contents
and the state of the
output following the event. Each one is explained below:
RST
Power-on Reset - On POR, all internal logic is reset, and registers are cleared to their default state (see
tables 10.x). Because Value RAM is typically the first area programmed upon power-up, it does not have
a defined state upon POR. Also, on POR, the
output will be pulled to an active low state for 20 ms
RST
(minimum).
A POR occurs every time V
crosses the voltage level approximately equivalent to the sum of one n-
DD
channel threshold (V
) and one p-channel threshold (V
), on a power-up or power-down condition.
TN
TP
DS1780 SRAM contents get “scrambled” when V
falls below the greater of one n-channel V
or one p-
DD
T
channel V
. Therefore, SRAM contents will always be in a defined state as supply voltage reaches the
T
minimum spec level of 2.8V, even in a power supply brownout condition.
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