전자부품 데이터시트 검색엔진 |
|
ADM1028 데이터시트(PDF) 10 Page - Analog Devices |
|
ADM1028 데이터시트(HTML) 10 Page - Analog Devices |
10 / 16 page REV. A ADM1028 –10– to the Fan Speed Register, the counter begins counting up or down (depending on whether the current value is greater or less than the target value). The counter will then count at the rate specified by the ramp rate bits of the Fan Speed Ramp Register. Once the counter reaches the target value the counter will stop counting. The FAN_SPD value is derived from the output of the counter. If a new value is written to the Fan Speed Register while a ramp function is occurring, the counter may change count direction to reach the new target value. The operation of THERM is independent of the fan speed ramping mechanism. Thus, THERM will assert immediately for over-temperature conditions. FAN SPEED RAMP RATE REGISTER COUNTER (CURRENT SPEED) DAC COMPARE FAN SPEED REGISTER RAMP ENABLE RAMP RATE UP/DOWN START/STOP FAN SPD Figure 6. THE ADM1028 INTERRUPT SYSTEM The ADM1028 has three interrupt outputs, INT, THERMA and THERMB. These have different functions. INT responds to violations of software programmed temperature limits and its interrupt sources are maskable, as described in more detail later. Interrupts and status bits are only set if a limit is exceeded for at least three consecutive conversions. Operation of the INT output is illustrated in Figure 7. Assum- ing that the temperature starts off within the programmed limits and that temperature interrupt sources are not masked, INT will go low if the temperature measured by the external sensor goes outside the programmed high or low temperature limit for the sensor. INT also goes low whenever THERM is low. 100 C 90 C 80 C 70 C 60 C 50 C 40 C INT TEMP LOW LIMIT HIGH LIMIT THIGH INTERRUPT LOGIC REARMED HERE * INT CLEARED BY SOFTWARE ** Figure 7. Operation of INT Output Once the interrupt has been cleared, it will not be reasserted even if the temperature remains outside the limit previously exceeded. However, INT will be rearmed if the temperature falls back within the set limits for three consecutive conversions. Once the INT function has been rearmed, it will then be reasserted once a limit is exceeded for three consecutive conversions. FAULT TOLERANT FAN CONTROL The ADM1028 incorporates a fault tolerant fan control capability that is tied to operation of the THERMA, THERMB outputs. It can override the setting of the analog output and force it to maximum to give full fan speed in the event of a critical over- temperature problem, even if, for some reason, this has not been handled by the system software. There are two temperature set point registers that will activate the fault tolerant fan control. One of these limits is program- mable by the user and one is a hardware (read-only) register that will operate if the user does not program any limit. The fault tolerant fan control is activated if a limit is exceeded for three or more consecutive readings. These limits are separate from the normal high and low temperature limits for the INT output, which do not affect the fault tolerant fan control or THERM outputs. A hardware limit of 100 °C is programmed into the register at address 18h, for the remote diode Default THERM limit. This is the default limit and the analog output will be forced to full- scale if the remote sensor reads more than 100 °C. This makes the fault tolerant fan control fail-safe in that it will operate at this temperature even if the user has programmed no other limit, or in the event of a software malfunction. Similarly, the Default Internal Temp THERM limit held in register 17h, forces the analog output full-scale if the ambient temperature measured is more than 70 °C. The user may override the default limits by programming a new limit into register 14h for the remote sensor and a new limit into register 13h for the internal sensor. The default value in register 14h is the same as for the read-only register (100 °C), but it may be programmed with higher or lower values. Once registers 13h and 14h have been programmed, or if the defaults are acceptable, Bit 3 of the configuration register must be set to “1.” This bit is a write-once bit that can only be writ- ten to “1,” and it has two effects: 1. It makes the values in registers 13h and 14h the active limits, and disables read-only registers 17h and 18h. 2. It locks the data into registers 13h and 14h, so that it cannot be changed until the lock bit is reset, either when AUXRST or RST is asserted, or a Power-On Reset occurs. Once the hardware override of the analog output is triggered, it will only return to normal operation after three consecutive measurements that are 5 degrees lower than the set limit. Whenever FAN_SPD output is forced to full-scale, the FAN_OFF output is negated. FAN SPEED RAMPING The ADM1028 device contains a Fan Speed Ramping mechanism that is accomplished using an 8-bit counter and a control register. On power-up, or an assertion of RST or AUXRST, the Fan Speed Register, counter, and Fan Speed Ramp Register are initialized to 0x00. The fan speed ramping mechanism is disabled by default and any value written to the Fan Speed Register is immediately reflected on the FAN_SPD output. Setting Bit 0 of the Fan Speed Ramp Rate Register enables the ramping mecha- nism. The counter is then preloaded with the current value contained in the Fan Speed Register, which prevents the fan speed from changing until a new value is written to the Fan Speed Register. When a new target Fan Speed Value is written |
유사한 부품 번호 - ADM1028 |
|
유사한 설명 - ADM1028 |
|
|
링크 URL |
개인정보취급방침 |
ALLDATASHEET.CO.KR |
ALLDATASHEET 가 귀하에 도움이 되셨나요? [ DONATE ] |
Alldatasheet는? | 광고문의 | 운영자에게 연락하기 | 개인정보취급방침 | 링크교환 | 제조사별 검색 All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |