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ADM1026JSTZ View Datasheet(PDF) - Analog Devices

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ADM1026JSTZ Datasheet PDF : 56 Pages
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Note that the THERM pin is bidirectional, so THERM may be
pulled low externally as an input. This causes the PWM and
DAC outputs to go to full scale until THERM is returned high
again. To disable THERM as an input, set Bit 0 of Configuration
Register 3 (Reg. 07h). This configures Pin 42 as GPIO16 and
prevents a low on Pin 42 from driving the fans at full speed.
THERM LIMIT
THERM LIMIT – 5°C
TEMPERATURE
THERM
INT
INT CLEARED BY STATUS REG 1 READ,
BIT 2 OF CONFIG. REG. 1 SET, OR ARA
Figure 54. Assertion of INT Due to THERM Event
Reset Input and Outputs
The ADM1026 has two active low, power-on reset outputs,
RESETMAIN and RESETSTBY. These operate as follows.
RESETSTBY monitors 3.3 V STBY. At power-up, RESETSTBY is
asserted (pulled low) until 180 ms after 3.3 V STBY rises above
the reset threshold.
RESETMAIN monitors 3.3 V MAIN. This means that at power-
up, RESETMAIN is asserted (pulled low) until 180 ms after
3.3 V MAIN rises above the reset threshold.
If 3.3 V MAIN rises with or before DVCC, RESETMAIN
remains asserted until 180 ms after RESETSTBY is negated.
RESETMAIN can also function as a RESET input. Pulling this
pin low resets the registers, which are initialized to their default
values by a software reset. (See the Software Reset Function
section for register details).
Note that the 3.3 V STBY pin supplies power to the ADM1026.
In applications that do not require monitoring of a 3.3 V STBY
and 3.3 V MAIN supply, these two pins should be connected
together (3.3 V MAIN should not be left floating).
To ensure that the 3.3 V STBY pin does not become backdriven,
the 3.3 V STBY supply should power on before all other voltages
in the system.
See Table 3 for more information about pin configuration.
ADM1026
3.3VSTBY ~1V
3.3VMAIN ~1V
RESETSTBY
RESETMAIN
180ms
180ms
POWER-ON RESET
Figure 55. Operation of Offset Outputs
NAND TREE TESTS
A NAND tree is provided in the ADM1026 for automated test
equipment (ATE) board-level connectivity testing. This allows
the functionality of all digital inputs to be tested in a simple
manner and any pins that are nonfunctional or shorted together
to be identified. The structure of the NAND tree is shown in
Figure 56. The device is placed into NAND tree test mode by
powering up with Pin 25 held high. This pin is sampled
automatically after power-up, and if it is connected high, then
the NAND test mode is invoked.
GPIO8
FAN0
GPIO9
FAN1
GPIO10
FAN2
GPIO11
INT
GPIO12
FAN3
CI
GPIO13
FAN4
SDA
FAN5
GPIO14
SCL
FAN6
GPIO15
FAN7
GPIO16
NTESTOUT
Figure 56. NAND Tree
The NAND tree test may be carried out in one of two ways.
1. Start with all inputs low and take them high in turn,
starting with the input nearest to NTEST_OUT
(GPIO16/THERM) and working back up the tree to the
input furthest from NTESTOUT (INT). This should give
the characteristic output pattern shown in Figure 57, with
NTESTOUT toggling each time an input is taken high.
2. Start with all inputs high and take them low in turn,
starting with the input furthest from NTEST_OUT (INT)
and working down the tree to the input nearest to
NTEST_OUT (GPIO16/ THERM). This should give a
similar output pattern to Figure 58.
Rev. A | Page 31 of 56
 

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