Rainbow Electronics MAX6661 - Manual (Page 12)

MAX6661
present. Bits 2 through 6 of the status register are
cleared by any successful read of the status register,
unless the fault persists. The ALERT output follows the
status flag bit. Both are cleared when successfully
read, but if the condition still exists, the ALERT and the corresponding status bit are reasserted at the end of
the next conversion.
When autoconverting, if the T HIGH and T LOW limits are
close together, it is possible for both high-temperature
and low-temperature status bits to be set, depending
Remote Temperature-Controlled Fan-Speed
Regulator with SPI-Compatible Interface
12 ______________________________________________________________________________________
BIT NAME POR STATE DESCRIPTION
7(MSB) ALERT Mask 0 When set to 1, ALERT is masked from internally generated errors.
6 Run/Stop 0 When set to 1, the MAX6661 enters low-power standby.
5 OVERT Polarity 0 0 provides active low, 1 provides active high.
4 Write Protect 0
When set to 1, Write Protect is in effect for the following applicable registers:
1. Configuration register bits 6, 5, 4, 3
2. T
MAX register
3. T HYST register
4. Fan conversion rate register
3
Thermal Closed/
Open Loop
0
When set to 1, the thermal loop is open. The fan speed control retains the
last closed-loop value unless overwritten by a bus command (in closed
loop, the fan speed control is read only). If fan mode is set to open loop by
writing a 1 to bit 0 of the fan gain register, then this bit is automatically set.
2 OVERT Input Inhibit 0
When set to 1, an external signal on OVERT is masked from bit 1 of the
status register.
1
Mask OVERT
Output
0 Mask the OVERT output from an internally generated overtemperature error.
0 N/A 0 Not used.
Table 4. Configuration Register Bit Assignments
BIT NAME POR STATE DESCRIPTION
7(MSB)
MAX6661
Overheat
0
When high, indicates that the fan driver transistor of the MAX6661 has
overheated (temperature > +150°C) and is in thermal shutdown. The fan driver
remains disabled until temperature falls below +140°C.
6 ALERT 0
When high, indicates ALERT has been activated (pulled low), regardless of
cause (internal or external).
5
Fan Driver Full
Scale
0
When high, indicates the fan driver is at full scale. Only valid in fan
closed-loop mode.
4 Remote High 0
When high, the remote-junction temperature exceeds the temperature in the
remote high register.
3 Remote Low 0
When low, the remote-junction temperature is lower than the temperature in the
remote low register.
2 Diode Open 0 When high, the remote-junction diode is open.
1 OVERT 0
When active, indicates that OVERT has been activated, regardless of cause
(internal or external).
0 Fan Failure 0
When high, indicates the count in the fan tachometer period register is higher
than the limit set in the fan tachometer period limit register.
Table 5. Status Register Bit Assignments