Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

EMC2300 Datasheet(PDF) 51 Page - SMSC Corporation

Part No. EMC2300
Description  Fan Control Device with High Frequency PWM and Temperature Monitors
Download  81 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  SMSC [SMSC Corporation]
Homepage  http://www.smsc.com
Logo 

EMC2300 Datasheet(HTML) 51 Page - SMSC Corporation

Zoom Inzoom in Zoom Outzoom out
 51 / 81 page
background image
Fan Control Device with High Frequency PWM and Temperature Monitors
Datasheet
SMSC EMC2300
51
Revision 0.2 (06-14-06)
DATASHEET
The Fan Tachometer Reading registers contain the number of 11.111
μs periods (90KHz) between full
fan revolutions. Fans produce two tachometer pulses per full revolution. These registers are updated
at least once every second.
To convert the value in the TACH reading registers to a representative RPM value is a simple
mathematical exercise. The 16bit reading is first converted to a decimal number and then multiplied
by the clock period (11.11
μs). This gives the measured period of two full TACH pulses which equals
1 full fan revolution. This number is then inverted and multiplied by 60 to give Rotations / minute.
For example: If the Tach 1 data bytes contain 0C86h (MSB followed by LSB). This is equivalent to
3206 clock counts. Multiplying this number by 11.111
μs (clock period) yields 0.03562s. This number
represents the measured time for two full periods of the TACH signal. Inverting this number and
multiplying it by 60 yields a final RPM value of 1684.
The larger the returned count, the slower the measured fan speed. The slowest fan speed that can be
stored is approximately 82RPM with an output code of FFFDh. This slow speed is not practical to
measure in TACH monitoring Mode 2 (see Table 7.2 on page 42 and Table 7.3 on page 43 for minimum
RPM’s measured using Mode 2 and Section 7.1.4.4, "Mode 2 – Monitor Tach input When PWM is
‘ON’," on page 39 for a description of this monitoring mode).
This value is represented for each fan in a 16 bit, unsigned number.
The Fan Tachometer Reading registers always return an accurate fan tachometer measurement, even
when a fan is disabled or non-functional, including when the start bit=0.
When one byte of a 16-bit register is read, the other byte latches the current value until it is read, in
order to ensure a valid reading. The order is LSB first, MSB second.
FFFFh indicates that the fan is not spinning, or the tachometer input is not connected to a valid signal
(This could be triggered by a counter overflow).
FFFEh, if the SLOW bit in the corresponding TACHx Option register is set (see Section 8.2.27,
"Registers 90h-93h: TachX Option Registers," on page 72 for details), indicates that fan is spinning,
but too slowly to be measured at the current TACH settings.
These registers are read only – a write to these registers has no effect.
8.2.4
Registers 30-32h: Current PWM Duty
Note 8.8
These registers are only writable when the associated fan is in manual mode. These
registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
The Current PWM Duty registers store the duty cycle that the chip is currently driving the PWM signals
at. At initial power-on, the duty cycle is 100% and thus, when read, this register will return FFh. After
the Ready/Lock/Start Register Start bit is set, this register and the PWM signals are updated based
Table 8.7 Registers 30-32h: Current PWM Duty
Register
Address
Read/
Write
Register Name
Bit 7
(MSb)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
(LSb)
Default
Value
30h
R
/W
(See
Note 8.8)
PWM1 Current Duty Cycle
7
6
5
4
3
2
1
0
N/A
31h
R
/W
(See
Note 8.8)
PWM2 Current Duty Cycle
7
6
5
4
3
2
1
0
N/A
32h
R
/W
(See
Note 8.8)
PWM3 Current Duty Cycle
7
6
5
4
3
2
1
0
N/A


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65  66  67  68  69  70  71  72  73  74  75  76  77  78  79  80  81 


Datasheet Download




Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Alldatasheet API   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
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