SMSC EMC2301 Rpm-based pwm fan controller Datasheet

EMC2301
RPM-Based PWM Fan Controller
PRODUCT FEATURES
Datasheet
General Description
Features
The EMC2301 is an SMBus compliant fan controller with
a PWM fan driver. The fan driver is controlled by a
programmable frequency PWM driver and Fan Speed
Control algorithm that operates in either a closed loop
fashion or as a directly PWM-controlled device.
„
Each closed loop Fan Speed Control algorithm (FSC)
has the capability to detect aging fans and alert the
system. It will likewise detect stalled or locked fans and
trigger an interrupt.
Additionally, the EMC2301 offers a clock output so that
multiple devices may be chained and slaved to the
same clock source for optimal performance in large
distributed systems.
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„
„
—
—
—
—
—
—
„
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Servers
Projectors
Industrial and Networking Equipment
Notebook Computers
4-wire fan compatible
High speed PWM (26 kHz)
Low speed PWM (9.5Hz - 2240 Hz)
Optional detection of aging fans
Fan Spin Up Control and Ramp Rate Control
Alert on Fan Stall
Watchdog Timer
RPM-based fan control algorithm
— 0.5% accuracy from 500 RPM to 16k RPM (external
crystal oscillator)
— 1% accuracy from 500 RPM to 16k RPM (internal clock)
„
SMBus 2.0 Compliant
„
CLK Pin can provide a clock source output
Available in an 8-pin MSOP Lead-free RoHS
Compliant package
— SMBus Alert compatible
„
Applications
Programmable Fan Control circuit (EMC2301)
Block Diagram
CLK
TACH
Tach
Measurement
Tachometer
Limit
Registers
SMBus
Slave
Protocol
PWM
SMSC EMC2301
PWM
Drivers
SMCLK
SMDATA
ALERT#
Fan Speed Control Algorithm
DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
Order Number:
ORDERING NUMBER
EMC2301-1-ACZL-TR
PACKAGE
FEATURES
8-pin MSOP (Lead-free
RoHS compliant)
One RPM-based fan speed control algorithm
This product meets the halogen maximum concentration values per IEC61249-2-21
For RoHS compliance and environmental information, please visit www.smsc.com/rohs
80 ARKAY DRIVE, HAUPPAUGE, NY 11788 (631) 435-6000 or 1 (800) 443-SEMI
Copyright © 2011 SMSC or its subsidiaries. All rights reserved.
Circuit diagrams and other information relating to SMSC products are included as a means of illustrating typical applications. Consequently, complete information sufficient for
construction purposes is not necessarily given. Although the information has been checked and is believed to be accurate, no responsibility is assumed for inaccuracies. SMSC
reserves the right to make changes to specifications and product descriptions at any time without notice. Contact your local SMSC sales office to obtain the latest specifications
before placing your product order. The provision of this information does not convey to the purchaser of the described semiconductor devices any licenses under any patent
rights or other intellectual property rights of SMSC or others. All sales are expressly conditional on your agreement to the terms and conditions of the most recently dated
version of SMSC's standard Terms of Sale Agreement dated before the date of your order (the "Terms of Sale Agreement"). The product may contain design defects or errors
known as anomalies which may cause the product's functions to deviate from published specifications. Anomaly sheets are available upon request. SMSC products are not
designed, intended, authorized or warranted for use in any life support or other application where product failure could cause or contribute to personal injury or severe property
damage. Any and all such uses without prior written approval of an Officer of SMSC and further testing and/or modification will be fully at the risk of the customer. Copies of
this document or other SMSC literature, as well as the Terms of Sale Agreement, may be obtained by visiting SMSC’s website at http://www.smsc.com. SMSC is a registered
trademark of Standard Microsystems Corporation (“SMSC”). Product names and company names are the trademarks of their respective holders.
SMSC DISCLAIMS AND EXCLUDES ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY AND ALL IMPLIED WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND AGAINST INFRINGEMENT AND THE LIKE, AND ANY AND ALL WARRANTIES ARISING FROM ANY COURSE
OF DEALING OR USAGE OF TRADE. IN NO EVENT SHALL SMSC BE LIABLE FOR ANY DIRECT, INCIDENTAL, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIAL
DAMAGES; OR FOR LOST DATA, PROFITS, SAVINGS OR REVENUES OF ANY KIND; REGARDLESS OF THE FORM OF ACTION, WHETHER BASED ON CONTRACT;
TORT; NEGLIGENCE OF SMSC OR OTHERS; STRICT LIABILITY; BREACH OF WARRANTY; OR OTHERWISE; WHETHER OR NOT ANY REMEDY OF BUYER IS HELD
TO HAVE FAILED OF ITS ESSENTIAL PURPOSE, AND WHETHER OR NOT SMSC HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Revision 1.3 (05-18-11)
2
DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Table of Contents
Chapter 1 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1
2.2
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
SMBus Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter 3 Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1
3.2
System Management Bus Interface Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1
SMBus Start Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2
SMBus Address and RD / WR Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.3
SMBus Data Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.4
SMBus ACK and NACK Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.5
SMBus Stop Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.6
SMBus Time-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.7
SMBus and I2C Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SMBus Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1
Write Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2
Read Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3
Send Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4
Receive Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.5
Block Write Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.6
Block Read Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.7
Alert Response Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
12
12
12
12
13
13
13
13
13
14
14
14
14
15
15
Chapter 4 Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Fan Control Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Fan Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RPM-based Fan Speed Control Algorithm (FSC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.1
Programming the RPM-based Fan Speed Control Algorithm . . . . . . . . . . . . . . . . . . . . .
Tachometer Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.1
Stalled Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.2
Aging Fan or Invalid Drive Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CLK Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.1
External Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.2
Internal Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spin Up Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8.1
Power Up Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8.2
Continuous Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
17
17
18
18
18
19
19
19
19
19
20
21
21
22
Chapter 5 Register Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.1
5.2
5.3
Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1.1
Lock Entries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.1
Fan Status - 24h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.2
Fan Stall Status - 25h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.3
Fan Spin Status - 26h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.4
Fan Drive Fail Status - 27h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SMSC EMC2301
3
DATASHEET
23
24
25
25
26
26
26
26
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
5.22
Fan Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.1
PWM Polarity Config - 2Ah . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.2
PWM Output Config - 2Bh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Base Frequency Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Setting Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Divide Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Configuration 1 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Configuration 2 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gain Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Spin Up Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Max Step Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Minimum Drive Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Valid TACH Count Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Drive Fail Band Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TACH Target Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TACH Reading Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Software Lock Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manufacturer ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Revision Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
27
27
27
28
28
29
29
31
32
33
34
35
35
36
36
37
37
38
38
38
Chapter 6 Typical Operating Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Chapter 7 Package Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
7.1
7.2
EMC2301 Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Package Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Chapter 8 Datasheet Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Revision 1.3 (05-18-11)
4
DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
List of Figures
Figure 1.1
Figure 3.1
Figure 4.1
Figure 4.2
Figure 4.3
Figure 7.1
Figure 7.2
EMC2301 Pin Diagram (8 pin MSOP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
SMBus Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
System Diagram of EMC2301 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Spin Up Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
EMC2301 Package Drawing - 8-Pin MSOP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
EMC2301 Package Markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SMSC EMC2301
5
DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
List of Tables
Table 1.1 Pin Description for EMC2301 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Table 1.2 Pin Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 2.1 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 2.2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 2.3 SMBus Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 3.1 Protocol Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 3.2 Write Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 3.3 Read Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 3.4 Send Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 3.5 Receive Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 3.6 Block Write Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 3.7 Block Read Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 3.8 Alert Response Address Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 4.1 Fan Controls Active for Operating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 5.1 EMC2301 Register Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 5.2 Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 5.3 Fan Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 5.4 Fan Interrupt Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Table 5.5 PWM Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Table 5.6 PWM Base Frequency Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 5.7 PWM_BASEx[1:0] Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 5.8 Fan Driver Setting Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 5.9 PWM Divide Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 5.10 Fan Configuration 1 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 5.11 Range Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 5.12 Minimum Edges for Fan Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Table 5.13 Update Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Table 5.14 Fan Configuration 2 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Table 5.15 Derivative Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Table 5.16 Error Range Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.17 Gain Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.18 Gain Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.19 Fan Spin Up Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Table 5.20 DRIVE_FAIL_CNT[1:0] Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Table 5.21 Spin Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Table 5.22 Spin Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 5.23 Fan Max Step Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 5.24 Minimum Fan Drive Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 5.25 Valid TACH Count Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 5.26 Fan Drive Fail Band Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table 5.27 TACH Target Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table 5.28 TACH Reading Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 5.29 Software Lock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 5.30 Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Table 5.31 Manufacturer ID Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Table 5.32 Revision Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Table 8.1 Customer Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
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RPM-Based PWM Fan Controller
Datasheet
Chapter 1 Pin Description
SMDATA
1
SMCLK
2
VDD
3
GND
4
8 ALERT#
EMC2301
8-MSOP
7 CLK
6
TACH
5 PWM
Figure 1.1 EMC2301 Pin Diagram (8 pin MSOP)
Table 1.1 Pin Description for EMC2301
PIN NUMBER
PIN NAME
PIN FUNCTION
PIN TYPE
1
SMDATA
SMBus data input/output - requires
external pull-up resistor
DIOD (5V)
2
SMCLK
SMBus clock input - requires external
pull-up resistor
DI (5V)
3
VDD
Power Supply
Power
4
GND
Ground
Power
Push-Pull PWM output driver for the Fan
DO
5
PWM
Open Drain PWM output driver for the Fan
OD (5V)
Open drain tachometer input for the Fan requires pull-up resistor
DI (5V)
Clock input for tachometer measurement
DI (5V)
Push-Pull Clock output to other fan
controllers to synchronize Fan Speed
Control
DO
Active low interrupt - requires external
pull-up resistor.
OD (5V)
6
TACH
7
CLK
8
ALERT#
The pin types are described in detail below. All pins labeled with (5V) are 5V tolerant.
APPLICATION NOTE: For the 5V tolerant pins that have a pull-up resistor, the voltage difference between VDD and
the 5V tolerant pad must never be more than 3.6V.
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Datasheet
Table 1.2 Pin Types
Revision 1.3 (05-18-11)
PIN TYPE
DESCRIPTION
Power
This pin is used to supply power or ground to the device.
DI
Digital Input - this pin is used as a digital input. This pin is
5V tolerant.
DO
Push / Pull Digital Output - this pin is used as a digital
output. It can both source and sink current.
DIOD
Digital Input / Open Drain Output this pin is used as a
digital I/O. When it is used as an output, it is open drain
and requires a pull-up resistor. This pin is 5V tolerant.
OD
Open Drain Digital Output - this pin is used as a digital
output. It is open drain and requires a pull-up resistor. This
pin is 5V tolerant.
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SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Chapter 2 Electrical Specifications
Table 2.1 Absolute Maximum Ratings
Voltage on 5V tolerant pins (V5VT_pin)
-0.3 to 5.5
V
Voltage on 5V tolerant pins (|V5VT_pin - VDD|) (see Note 2.1)
0 to 3.6
V
Voltage on VDD pin
-0.3 to 4
V
Voltage on any other pin to GND
-0.3 to VDD + 0.3
V
Package Thermal Resistance - Junction to Ambient (θJA)
141
°C/W
Operating Ambient Temperature Range
-40 to 125
°C
Storage Temperature Range
-55 to 150
°C
ESD Rating, All Pins, HBM
2000
V
Note: Stresses above those listed could cause permanent damage to the device. This is a stress
rating only and functional operation of the device at any other condition above those indicated
in the operation sections of this specification is not implied.
Note 2.1
2.1
For the 5V tolerant pins that have a pull-up resistor, the pull-up voltage must not exceed
3.6V when the EMC2301 is unpowered.
Electrical Specifications
Table 2.2 Electrical Specifications
VDD = 3V to 3.6V, TA = -40°C to 125°C, all Typical values at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
MIN
TYP
MAX
UNIT
3.3
3.6
V
350
475
uA
CONDITIONS
DC Power
Supply Voltage
VDD
Supply Current
IDD
3
PWM Fan Driver
PWM Resolution
PWM
PWM Duty Cycle
DUTY
256
Steps
0
100
%
RPM-based Fan Controller
Tachometer Range
Tachometer Setting
Accuracy
Input High Voltage
SMSC EMC2301
TACH
480
16000
RPM
ΔTACH
±0.5
±1
%
External oscillator 32.768kHz
ΔTACH
±1
±2
%
Internal Oscillator
VIH
2.0
V
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Datasheet
Table 2.2 Electrical Specifications (continued)
VDD = 3V to 3.6V, TA = -40°C to 125°C, all Typical values at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
Input Low Voltage
VIL
Output High Voltage
Output Low Voltage
MIN
TYP
MAX
UNIT
0.8
V
VDD 0.4
VOH
8 mA current drive
V
0.4
VOL
V
8 mA current sink
uA
ALERT# pin
Powered and unpowered
0°C < TA < 85°C
pull-up voltage < 3.6V
Leakage current
ILEAK
Note 2.2
2.2
±5
CONDITIONS
All voltages are relative to ground.
SMBus Electrical Specifications
Table 2.3 SMBus Electrical Specifications
VDD= 3V to 3.6V, TA = -40°C to 125°C Typical values are at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
MIN
TYP
MAX
UNITS
CONDITIONS
SMBus Interface
Input High Voltage
VIH
Input Low Voltage
VIL
Output High Voltage
Output Low Voltage
Input High/Low Current
Input Capacitance
VOH
2.0
V
0.8
VDD
- 0.4
V
V
VOL
0.4
V
4 mA current sink
IIH / IIL
±5
uA
Powered and unpowered
0°C < TA < 85°C
CIN
5
pF
SMBus Timing
Clock Frequency
fSMB
10
400
kHz
50
ns
Spike Suppression
tSP
Bus free time Start to
Stop
tBUF
1.3
us
Setup Time: Start
tSU:STA
0.6
us
Setup Time: Stop
tSU:STP
0.6
us
Data Hold Time
tHD:DAT
0
us
Data Setup Time
tSU:DAT
0.6
us
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RPM-Based PWM Fan Controller
Datasheet
Table 2.3 SMBus Electrical Specifications (continued)
VDD= 3V to 3.6V, TA = -40°C to 125°C Typical values are at TA = 27°C unless otherwise noted.
CHARACTERISTIC
SYMBOL
MIN
Clock Low Period
tLOW
1.3
us
Clock High Period
tHIGH
0.6
us
Clock/Data Fall time
tFALL
300
ns
Min = 20+0.1CLOAD ns
Clock/Data Rise time
tRISE
300
ns
Min = 20+0.1CLOAD ns
CLOAD
400
pF
per bus line
Capacitive Load
SMSC EMC2301
TYP
MAX
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DATASHEET
UNITS
CONDITIONS
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
Chapter 3 Communications
3.1
System Management Bus Interface Protocol
The EMC2301 communicates with a host controller, such as an SMSC SIO, through the SMBus. The
SMBus is a two-wire serial communication protocol between a computer host and its peripheral
devices. A detailed timing diagram is shown in Figure 3.1. Stretching of the SMCLK signal is supported;
however, the EMC2301 will not stretch the clock signal.
TLOW
THIGH
THD:STA
TSU:STO
TRISE
SMCLK
THD:STA
TFALL
THD:DAT
TSU:STA
TSU:DAT
SMDATA
TBUF
P
S
S
S - Start Condition
P - Stop Condition P
Figure 3.1 SMBus Timing Diagram
3.1.1
SMBus Start Bit
The SMBus Start bit is defined as a transition of the SMBus Data line from a logic ‘1’ state to a logic
‘0’ state while the SMBus Clock line is in a logic ‘1’ state.
3.1.2
SMBus Address and RD / WR Bit
The SMBus Address Byte consists of the 7-bit client address followed by a RD / WR indicator bit. If
this RD / WR bit is a logic ‘0’, then the SMBus Host is writing data to the client device. If this RD / WR
bit is a logic ‘1’, then the SMBus Host is reading data from the client device.
The SMBus address is set at 0101_111(r/w)b.
3.1.3
SMBus Data Bytes
All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.
3.1.4
SMBus ACK and NACK Bits
The SMBus client will acknowledge all data bytes that it receives (as well as the client address if it
matches and the ARA address if the ALERT# pin is asserted). This is done by the client device pulling
the SMBus Data line low after the 8th bit of each byte that is transmitted.
The Host will NACK (not acknowledge) the data received from the client by holding the SMBus data
line high after the 8th data bit has been sent.
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RPM-Based PWM Fan Controller
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3.1.5
SMBus Stop Bit
The SMBus Stop bit is defined as a transition of the SMBus Data line from a logic ‘0’ state to a logic
‘1’ state while the SMBus clock line is in a logic ‘1’ state. When the EMC2301 detects an SMBus Stop
bit has been communicating with the SMBus protocol, it will reset its client interface and prepare to
receive further communications.
3.1.6
SMBus Time-out
The EMC2301 includes an SMBus timeout feature. Following a 30ms period of inactivity on the
SMBus, the device will time-out and reset the SMBus interface.
The SMBus timeout feature is disabled by default and can be enabled via clearing the DIS_TO bit in
the Configuration register (20h).
3.1.7
SMBus and I2C Compliance
The major difference between SMBus and I2C devices is highlighted here. For complete compliance
information refer to the SMBus 2.0 specification.
1. Minimum frequency for SMBus communications is 10kHz (I2C has no minimum frequency).
2. The slave protocol will reset if the clock is held low for longer than 30ms (I2C has no timeout).
3. The slave protocol will reset if both the clock and data lines are held high for longer than 150us.
4. I2C devices do not support the Alert Response Address functionality (which is optional for SMBus).
5. The Block Read and Block Write protocols are only compliant with I2C data formatting. They do
not support SMBus formatting for Block Read and Block Write protocols.
3.2
SMBus Protocols
The EMC2301 is SMBus 2.0 compatible and supports Send Byte, Read Byte, Receive Byte and Write
Byte as valid protocols as shown below. It will respond to the Alert Response Address protocol but is
not in full compliance.
All of the below protocols use the convention in Table 3.1. When reading the protocol blocks, the value
of YYYY_YYYb should be replaced with the respective SMBus addresses.
Table 3.1 Protocol Format
DATA SENT
TO DEVICE
# of bits sent
3.2.1
DATA SENT TO
THE HOST
# of bits sent
Write Byte
The Write Byte is used to write one byte of data to the registers as shown below Table 3.2.
Table 3.2 Write Byte Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
REGISTER
DATA
ACK
STOP
1 -> 0
YYYY_YYYb
0
0
XXh
0
XXh
0
0 -> 1
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RPM-Based PWM Fan Controller
Datasheet
3.2.2
Read Byte
The Read Byte protocol is used to read one byte of data from the registers as shown in Table 3.3.
Table 3.3 Read Byte Protocol
START
SLAVE
ADDRESS
WR
ACK
Register
Address
ACK
START
Slave
Address
RD
ACK
Register
Data
NACK
STOP
1 -> 0
YYYY_YYYb
0
0
XXh
0
0 -> 1
YYYY_YYYb
1
0
XXh
1
0 -> 1
3.2.3
Send Byte
The Send Byte protocol is used to set the internal address register pointer to the correct address
location. No data is transferred during the Send Byte protocol as shown in Table 3.4.
Table 3.4 Send Byte Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
STOP
1 -> 0
YYYY_YYYb
0
0
XXh
0
0 -> 1
3.2.4
Receive Byte
The Receive Byte protocol is used to read data from a register when the internal register address
pointer is known to be at the right location (e.g. set via Send Byte). This is used for consecutive reads
of the same register as shown in Table 3.5.
Table 3.5 Receive Byte Protocol
START
SLAVE
ADDRESS
RD
ACK
REGISTER DATA
NACK
STOP
1 -> 0
YYYY_YYYb
1
0
XXh
1
0 -> 1
3.2.5
Block Write Protocol
The Block Write is used to write multiple data bytes to a group of contiguous registers as shown in
Table 3.6. It is an extension of the Write Byte Protocol.
Table 3.6 Block Write Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
REGISTER
DATA
ACK
1 ->0
YYYY_YYYb
0
0
XXh
0
XXh
0
REGISTER
DATA
ACK
REGISTER
DATA
ACK
...
REGISTER
DATA
ACK
STOP
XXh
0
XXh
0
...
XXh
0
0 -> 1
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RPM-Based PWM Fan Controller
Datasheet
3.2.6
Block Read Protocol
The Block Read is used to read multiple data bytes from a group of contiguous registers as shown in
Table 3.7. It is an extension of the Read Byte Protocol.
Table 3.7 Block Read Protocol
START
SLAVE
ADDRESS
WR
ACK
REGISTER
ADDRESS
ACK
START
SLAVE
ADDRESS
RD
ACK
REGISTER
DATA
1->0
YYYY_YYYb
0
0
XXh
0
1 ->0
YYYY_YYYb
1
0
XXh
ACK
REGISTER
DATA
ACK
REGISTER
DATA
ACK
REGISTER
DATA
ACK
...
REGISTER
DATA
NACK
STOP
0
XXh
0
XXh
0
XXh
0
...
XXh
1
0 -> 1
3.2.7
Alert Response Address
The ALERT# output can be used as a processor interrupt or as an SMBus Alert when configured to
operate as an interrupt.
When it detects that the ALERT# pin is asserted, the host will send the Alert Response Address (ARA)
to the general address of 0001_100xb. All devices with active interrupts will respond with their client
address as shown in Table 3.8.
Table 3.8 Alert Response Address Protocol
START
ALERT
RESPONSE
ADDRESS
RD
ACK
DEVICE
ADDRESS
NACK
STOP
1 -> 0
0001_100b
1
0
YYYY_YYYb
1
0 -> 1
The EMC2301 will respond to the ARA in the following way if the ALERT# pin is asserted.
1. Send Slave Address and verify that full slave address was sent (i.e. the SMBus communication
from the device was not prematurely stopped due to a bus contention event).
2. Set the MASK bit to clear the ALERT# pin.
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Chapter 4 Product Description
The EMC2301 is an SMBus compliant fan controller with a programmable frequency PWM fan driver.
The fan driver can be operated using two modes: the RPM-based Fan Speed Control Algorithm or the
direct fan drive setting.
Figure 4.1 shows a system diagram of the EMC2301.
3.3V
VDD
MCU
tachometer
TACH
SMCLK
Drive
Circuit
SMDATA
PWM
ALERT#
32.768KHz Clock
Input or Output
GND
CLK
EMC2301
Figure 4.1 System Diagram of EMC2301
4.1
Fan Control Modes of Operation
The EMC2301 has two modes of operation for the fan driver. Each mode of operation uses the Ramp
Rate control and Spin Up Routine.
1. Direct Setting Mode - in this mode of operation, the user directly controls the fan drive setting.
Updating the Fan Driver Setting Register (see Section 5.7) will instantly update the PWM fan drive.
Ramp Rate control is optional and enabled via the EN_RRC bits.
„
Whenever the Direct Setting Mode is enabled, the current drive will be changed to what was
last written into the Fan Driver Setting Register.
2. Fan Speed Control Mode (FSC) - in this mode of operation, the user determines a target
tachometer count and the PWM drive setting is automatically updated to achieve this target speed.
The algorithm uses the Spin Up Routine and has user definable ramp rate controls.
„
This mode is enabled setting the EN_ALGO bit in the Fan Configuration Register.
Table 4.1 Fan Controls Active for Operating Mode
DIRECT SETTING MODE
FSC MODE
Fan Driver Setting (read / write)
Fan Driver Setting (read only)
EDGES[1:0]
EDGES[1:0]
(Fan Configuration)
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SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Table 4.1 Fan Controls Active for Operating Mode (continued)
DIRECT SETTING MODE
FSC MODE
-
RANGE[1:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
LEVEL
(Spin Up Configuration)
LEVEL
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
Fan Step
Fan Step
-
Fan Minimum Drive
Valid TACH Count
Valid TACH Count
-
TACH Target (read / write)
TACH Reading
TACH Reading
-
DRIVE_FAIL_CNT[1:0] and Drive Band Fail Registers
4.2
PWM Fan Driver
The EMC2301 supports a PWM output driver. The output driver can be configured to operate as an
open-drain (default) or push-pull driver and the driver can be configured with normal or inverse polarity.
Additionally, the PWM frequencies is programmable with ranges from 9.5Hz to 26kHz in four
programmable frequency bands.
4.3
RPM-based Fan Speed Control Algorithm (FSC)
The EMC2301 includes an RPM-based Fan Speed Control Algorithm. The algorithm is controlled
manually (by setting the target fan speed).
This fan control algorithm uses Proportional, Integral, and Derivative terms to automatically approach
and maintain the system’s desired fan speed to an accuracy directly proportional to the accuracy of
the clock source.
The desired tachometer count is set by the user inputting the desired number of 32.768kHz cycles that
occur per fan revolution. This is done by manually setting the TACH Target Register. The user may
change the target count at any time. The user may also set the target count to FFh in order to disable
the fan driver for lower current operation.
For example, if a desired RPM rate for a 2-pole fan is 3000 RPMs, then the user would input the
hexidecimal equivalent of 1296 (51h in the TACH Target Register). This number represents the number
of 32.768KHz cycles that would occur during the time it takes the fan to complete a single revolution
when it is spinning at 3000RPMs.
The EMC2301’s RPM-based Fan Speed Control Algorithm has programmable configuration settings
for parameters such as ramp-rate control and spin up conditions. The fan driver automatically detects
and attempts to alleviate a stalled/stuck fan condition while also asserting the ALERT# pin. The
EMC2301 works with fans that operate up to 16,000 RPMs and provide a valid tachometer signal.
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RPM-Based PWM Fan Controller
Datasheet
The fan controller will function either with an externally supplied 32.768kHz clock source or with it’s
own internal 32kHz oscillator depending on the required accuracy. The EMC2301 offers a clock output
that enables additional devices to be slaved to the same clock source.
4.3.1
Programming the RPM-based Fan Speed Control Algorithm
The RPM-based Fan Speed Control Algorithm is disabled upon device power up. The following
registers control the algorithm. The EMC2301 fan control registers are pre-loaded with defaults that
will work for a wide variety of fans so only the TACH Target Register is required to set a fan speed.
The other fan control registers can be used to fine-tune the algorithm behavior based on application
requirements.
Note that steps 1 - 6 are optional and need only be performed if the default settings do not provide
the desired fan response.
1. Set the Spin Up Configuration Register to the Spin Up Level and Spin Time desired.
2. Set the Fan Step Register to the desired step size.
3. Set the Fan Minimum Drive Register to the minimum drive value that will maintain fan operation.
4. Set the Update Time and Edges options in the Fan Configuration Register.
5. Set the Valid TACH Count Register to the highest tach count that indicates the fan is spinning.
Refer to AN17.4 RPM to TACH Counts Conversion for examples and tables for supported RPM
ranges (500, 1k, 2k, 4k).
6. Set the TACH Target Register to the desired tachometer count.
7. Enable the RPM-based Fan Speed Control Algorithm by setting the EN_ALGO bit.
4.4
Tachometer Measurement
The tachometer measurement circuitry is used in conjunction with the RPM-based Fan Speed Control
Algorithm to update the fan driver output. Additionally, it can be used in Direct Setting mode as a
diagnostic for host based fan control.
This method monitors the TACHx signal in real time. It constantly updates the tachometer
measurement by reporting the number of clocks between a user programmed number of edges on the
TACHx signal (see Table 5.12).
The tachometer measurement provides fast response times for the RPM-based Fan Speed Control
Algorithm and the data is presented as a count value that represents the fan RPM period.
APPLICATION NOTE: The tachometer measurement method works independently of the drive settings. If the
device is put into Direct Setting and the fan drive is set at a level that is lower than the fan
can operate (including zero drive), then the tachometer measurement may signal a Stalled
Fan condition and assert an interrupt.
4.4.1
Stalled Fan
A Stalled fan is detected if the tach counter exceeds the user-programmable Valid TACH Count setting.
If a stall is detected, the device will flag the fan as stalled and trigger an interrupt.
If the RPM-based Fan Speed Control Algorithm is enabled, the algorithm will automatically attempt to
restart the fan until it detects a valid tachometer level or is disabled.
The FAN_STALL Status bit indicates that a stalled fan was detected. This bit is checked conditionally
depending on the mode of operation.
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RPM-Based PWM Fan Controller
Datasheet
4.4.2
„
Whenever the Direct Setting Mode or the Spin Up Routine is enabled, the FAN_STALL interrupt
will be masked for the duration of the programmed Spin Up Time (see Table 5.22) to allow the fan
to reach a valid speed without generating unnecessary interrupts.
„
In Direct Setting Mode, whenever the TACH Reading Register value exceeds the Valid TACH Count
Register setting, the FAN_STALL status bit will be set.
„
When using the RPM-based Fan Speed Control Algorithm, the stalled fan condition is checked
whenever the Update Time is met and the fan drive setting is updated. It is not a continuous check.
Aging Fan or Invalid Drive Detection
This is useful to detect aging fan conditions (where the fan’s natural maximum speed degrades over
time) or a speed setting that is faster than the fan is capable of. The EMC2301 contains circuitry that
detects that the programmed fan speed can be reached by the fan. If the target fan speed cannot be
reached within a user defined band of tach counts at maximum drive, the DRIVE_FAIL status bits are
set and the ALERT# pin is asserted.
4.5
CLK Pin
The CLK pin has multiple functionality as determined by the settings of the Configuration register.
4.5.1
External Clock
The EMC2301 allows the user to choose between supplying an external 32.768kHz clock or use of
the internal 32kHz oscillator to measure the tachometer signal. This clock source is used by the RPMbased Fan Speed Control Algorithm to calculate the current fan speed. This fan controller accuracy is
directly proportional to the accuracy of the clock source.
When this function is used, the external clock is driven into the device via the CLK pin.
4.5.2
Internal Clock
Alternately, the EMC2301 may be configured to use its internal clock as a clock output to drive other
fan driver devices. When configured to operate in this mode, the device uses its internal clock for
tachometer reading and drives the CLK pin using a push-pull driver.
4.6
Spin Up Routine
The EMC2301 also contains programmable circuitry to control the spin up behavior of the fan driver
to ensure proper fan operation.
The Spin Up Routine is initiated in Direct Setting mode when the setting value changes from 00h to
anything else.
When the Fan Speed Control Algorithm is enabled, the Spin Up Routine is initiated under the following
conditions:
1. The TACH Target Register value changes from a value of FFh to a value that is less than the Valid
TACH Count (see Section 5.15).
2. The RPM-based Fan Speed Control Algorithm’s measured TACH Reading Register value is greater
than the Valid TACH Count setting.
When the Spin Up Routine is operating, the fan driver is set to full scale (optional) for one quarter of
the total user defined spin up time. For the remaining spin up time, the fan driver output is set at a
user defined level (30% through 65% drive).
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After the Spin Up Routine has finished, the EMC2301 measures the TACHx signal. If the measured
TACH Reading Register value is higher than the Valid TACH Count Register setting, the FAN_SPIN
status bit is set and the Spin Up Routine will automatically attempt to restart the fan.
Figure 4.2 shows an example of the Spin Up Routine in response to a programmed fan speed change
based on the first condition above.
100%
(optional)
30% through 65%
Fan Step
New Target Count
Algorithm controlled drive
Prev Target
Count = FFh
¼ of Spin Up Time
Update Time
Spin Up Time
Check TACH
Target Count
Changed
Target Count
Reached
Figure 4.2 Spin Up Routine
4.7
Ramp Rate Control
The Fan Driver can be configured with automatic ramp rate control. Ramp rate control is accomplished
by adjusting the drive output settings based on the Maximum Fan Step Register settings and the
Update Time settings.
If the RPM-based Fan Speed Control Algorithm is used, then this ramp rate control is automatically
used. The user programs a maximum step size for the fan drive setting and an update time. The
update time varies from 100ms to 1.6s while the fan drive maximum step can vary from 1 count to 31
counts.
When a new fan drive setting is entered, the delta from the next fan drive setting and the previous fan
drive setting is determined. If this delta is greater than the Max Step settings, then the fan drive setting
is incrementally adjusted every 100ms to 1.6s as determined by the Update Time until the target fan
drive setting is reached. See Figure 4.3.
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RPM-Based PWM Fan Controller
Datasheet
Next Desired
Setting
Max
Step
Max
Step
Previous
Setting
Update
Time
Update
Time
Setting Changed
Figure 4.3 Ramp Rate Control
4.8
Watchdog Timer
The EMC2301 contains an internal Watchdog Timer for the fan driver. The Watchdog timer monitors
the SMBus traffic for signs of activity and works in two different modes based upon device operation.
These modes are Power Up Operation and Continuous Operation as described below.
For either mode of operation, if four (4) seconds elapse without activity detected by the host, then the
watchdog will be triggered and the following will occur:
1. The WATCH status bit will be set.
2. The fan driver will be set to full scale drive. It will remain at full scale drive until it is disabled.
3. The ALERT# pin is asserted.
APPLICATION NOTE: When the Watchdog timer is activated, the Fan Speed Control Algorithm is automatically
disabled. Disabling the Watchdog will not automatically set the fan drive nor re-activate the
Fan Speed Control Algorithm. This must be done manually.
4.8.1
Power Up Operation
The Watchdog Timer only starts immediately after power-up. Once it has been triggered or deactivated,
it will not restart although it can be configured to operate in Continuous operation. While the Watchdog
timer is active, the device will not check for a Stalled Fan condition.
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Datasheet
In the Power Up Operation, the Watchdog Timer is disabled by any of the following actions:
1. Writing the Fan Setting Register will disable the Watchdog Timer.
2. Enabling the RPM-based Fan Speed Control Algorithm by setting the EN_ALGO bit will disable the
Watchdog Timer. The fan driver will be set based on the RPM-based Fan Speed Control Algorithm.
Writing any other configuration registers will not disable the Watchdog Timer upon power up.
4.8.2
Continuous Operation
When configured to operate in Continuous Operation, the Watchdog timer will start immediately. The
timer will be reset by any access (read or write) to the SMBus register set. The four second Watchdog
timer will restart upon completion of SMBus activity.
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RPM-Based PWM Fan Controller
Datasheet
Chapter 5 Register Set
5.1
Register Map
The following registers are accessible through the SMBus Interface. All register bits marked as ‘-’ will
always read ‘0’. A write to these bits will have no effect.
Table 5.1 EMC2301 Register Set
ADDR
R/W
REGISTER
NAME
FUNCTION
DEFAULT
VALUE
LOCK
PAGE
Configuration and control
20h
R/W
Configuration
Configures the clocking and watchdog
functionality
40h
SWL
Page 25
24h
R-C
Fan Status
Stores the status bits for the RPMbased Fan Speed Control Algorithm
00h
No
Page 25
25h
R-C
Fan Stall Status
Stores status bits associated with a
stalled fan
00h
No
Page 25
26h
R-C
Fan Spin Status
Stores status bits associated with a
spin-up failure
00h
No
Page 25
27h
R-C
Drive Fail Status
Stores status bits associated with drive
failure
00h
No
Page 25
29h
R/W
Fan Interrupt
Enable Register
Controls the masking of interrupts on all
fan related channels
00h
No
Page 27
2Ah
R/W
PWM Polarity
Config
Configures Polarity of the PWM driver
00h
No
Page 27
2Bh
R/W
PWM Output
Config
Configures Output type of the PWM
driver
00h
No
Page 27
2Dh
R/W
PWM Base
Frequency
Selects the base frequency for the
PWM output
00h
No
Page 28
00h
No
Page 28
Fan Control Registers
30h
R/W
Fan Setting
Always displays the most recent fan
driver input setting for the Fan. If the
RPM-based Fan Speed Control
Algorithm is disabled, allows direct user
control of the fan driver.
31h
R/W
PWM Divide
Stores the divide ratio to set the
frequency for the Fan
01h
No
Page 29
32h
R/W
Fan Configuration
1
Sets configuration values for the RPMbased Fan Speed Control Algorithm for
the Fan driver
2Bh
No
Page 29
33h
R/W
Fan Configuration
2
Sets additional configuration values for
the Fan driver
28h
SWL
Page 31
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Table 5.1 EMC2301 Register Set (continued)
DEFAULT
VALUE
LOCK
PAGE
Holds the gain terms used by the RPMbased Fan Speed Control Algorithm for
the Fan driver
2Ah
SWL
Page 32
Fan Spin Up
Configuration
Sets the configuration values for Spin
Up Routine of the Fan driver
19h
SWL
Page 33
R/W
Fan Max Step
Sets the maximum change per update
for the Fan driver
10h
SWL
Page 34
38h
R/W
Fan Minimum
Drive
Sets the minimum drive value for the
Fan driver
66h
(40%)
SWL
Page 35
39h
R/W
Fan Valid TACH
Count
Holds the tachometer reading that
indicates Fan is spinning properly
F5h
SWL
Page 35
3Ah
R/W
Fan Drive Fail
Band Low Byte
00h
SWL
3Bh
R/W
Fan Drive Fail
Band High Byte
Stores the number of Tach counts used
to determine how the actual fan speed
must match the target fan speed at full
scale drive
3Ch
R/W
TACH Target Low
Byte
3Dh
R/W
3Eh
3Fh
ADDR
R/W
REGISTER
NAME
35h
R/W
Gain
36h
R/W
37h
FUNCTION
Page 36
00h
SWL
Holds the target tachometer reading low
byte for the Fan
F8h
No
Page 36
TACH Target High
Byte
Holds the target tachometer reading
high byte for the Fan
FFh
No
Page 36
R
TACH Reading
High Byte
Holds the tachometer reading high byte
for the Fan
FFh
No
Page 37
R
TACH Reading
Low Byte
Holds the tachometer reading low byte
for the Fan
F8h
No
Page 37
00h
SWL
Page 37
Lock Register
EF
R/W
Software Lock
Locks all SWL registers
Revision Registers
FDh
R
Product ID
Stores the unique Product ID
37h
No
Page 38
FEh
R
Manufacturer ID
Stores the Manufacturer ID
5Dh
No
Page 38
FFh
R
Revision
Revision
80h
No
Page 38
During Power-On-Reset (POR), the default values are stored in the registers. A POR is initiated when
power is first applied to the part and the voltage on the VDD supply surpasses the POR level as
specified in the electrical characteristics. Any reads to undefined registers will return 00h. Writes to
undefined registers will not have an effect.
5.1.1
Lock Entries
The Lock Column describes the locking mechanism, if any, used for individual registers. All SWL
registers are Software Locked and therefore made read-only when the LOCK bit is set.
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RPM-Based PWM Fan Controller
Datasheet
5.2
Configuration Register
Table 5.2 Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
20h
R/W
Configuration
MASK
DIS_TO
WD_EN
-
-
-
DR_EXT_
CLK
USE_
EXT_
CLK
40h
The Configuration Register controls the basic functionality of the EMC2301. The bits are described
below. The Configuration Register is software locked.
Bit 7 - MASK - Blocks the ALERT# pin from being asserted.
„
‘0’ (default) - The ALERT# pin is unmasked. If any bit in the status registers is set, the ALERT#
pin will be asserted (unless individually masked via the Fan Interrupt Enable Register).
„
‘1’ - The ALERT# pin is masked and will not be asserted.
Bit 6 - DIS_TO - Disables the SMBus timeout function for the SMBus client (if enabled).
„
‘0’ - The SMBus timeout function is enabled.
„
‘1’ (default) - The SMBus timeout function is disabled allowing the device to be fully I2C compliant.
Bit 5 - WD_EN - Enables the Watchdog timer (see Section 4.8) to operate in Continuous Mode.
„
‘0’ (default) - The Watchdog timer does not operate continuously. It will function upon power up and
at no other time (see Section 4.8.1).
„
‘1’ - The Watchdog timer operates continuously as described in Section 4.8.2.
Bit 1 - DR_EXT_CLK - Enables the internal tachometer clock to be driven out on the CLK pin so that
multiple devices can be synced to the same source.
„
‘0’ (default) - The CLK pin acts as a clock input.
„
‘1’ - The CLK pin acts as a clock output and is a push-pull driver.
Bit 0 - USE_EXT_CLK - Enables the EMC2301 to use a clock present on the CLK pin as the
tachometer clock. If the DR_EXT_CLK bit is set, then this bit is ignored and the device will use the
internal oscillator.
5.3
„
‘0’ (default) - The EMC2301 will use its internal oscillator for all Tachometer measurements.
„
‘1’ - The EMC2301 will use the oscillator presented on the CLK pin for all Tachometer
measurements.
Fan Status Registers
Table 5.3 Fan Status Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
24h
R-C
Fan Status
WATCH
-
-
-
-
DRIVE_
FAIL
FAN_
SPIN
FAN_
STALL
00h
25h
R-C
Fan Stall
Status
-
-
-
-
-
-
-
FAN_
STALL
00h
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Datasheet
Table 5.3 Fan Status Registers (continued)
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
26h
R-C
Fan Spin
Status
-
-
-
-
-
-
-
FAN_
SPIN
00h
27h
R-C
Fan Drive
Fail Status
-
-
-
-
-
-
DRIVE_
FAIL
00h
-
The Fan Status registers contain the status bits associated with the fan driver.
5.3.1
Fan Status - 24h
The Fan Status register indicates that the fan driver has stalled or failed or that the Watchdog Timer
has expired (see Section 4.8).
Bit 7 - WATCH - Indicates that the Watchdog Timer has expired. When set, the fan is driven to 100%
duty cycle and will remain at 100% duty cycle until it is programmed. This bit is cleared when it is read.
Bit 2 - DRIVE_FAIL - Indicates that the fan driver cannot meet the programmed fan speed at maximum
PWM duty cycle. This bit is set when the DRIVE_FAIL bit is set (in the Fan Drive Fail Status register).
This bit is cleared when the DRIVE_FAIL bit is cleared.
Bit 1 - FAN_SPIN - Indicates that the fan driver cannot spin up. This bit is set when the FAN_SPIN bit
is set (in the Fan Spin Status register). This bit is cleared when the FAN_SPIN bit is cleared.
Bit 0 - FAN_STALL - Indicates that the fan driver have stalled. This bit is set when the FAN_STALL bit
is set (in the Fan Stall Status register). This bit is cleared when the FAN_STALL bit is cleared.
5.3.2
Fan Stall Status - 25h
The Fan Stall Status register indicates that the fan driver has detected a stalled condition (see
Section 4.4.1). This bit is cleared upon a read if the error condition has been removed.
Bit 0 - FAN_STALL - Indicates that the Fan has stalled.
5.3.3
Fan Spin Status - 26h
The Fan Spin Status register indicates that the fan driver has failed to spin-up (see Section 4.6). This
bit is cleared upon a read if the error condition has been removed.
Bit 0 - FAN_SPIN - Indicates that the Fan has failed to spin up.
5.3.4
Fan Drive Fail Status - 27h
The Fan Drive Fail Status register indicates that the fan driver cannot drive to the programmed speed
even at 100% duty cycle (see Section 4.4.2 and Section 5.12). This bit is cleared upon a read if the
error condition has been removed.
Bit 0 - DRIVE_FAIL1 - Indicates that the Fan cannot reach its programmed fan speed even at 100%
duty cycle. This may be due to an aging fan or invalid programming.
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RPM-Based PWM Fan Controller
Datasheet
5.4
Fan Interrupt Enable Register
Table 5.4 Fan Interrupt Enable Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
29h
R/W
Fan
Interrupt
Enable
-
-
-
-
-
-
-
FAN_
INT_EN
00h
The Fan Interrupt Enable controls the masking for the Fan channel. When a channel is enabled, it will
cause the ALERT# pin to be asserted when an error condition is detected.
Bit 0 - FAN_INT_EN - Allows the Fan to assert the ALERT# pin if an error condition is detected.
5.5
„
‘0’ (default) - An error condition on Fanwill not cause the ALERT# pin to be asserted, however the
status registers will be updated normally.
„
‘1’ - An error condition (Stall, Spin Up, Drive Fail) on the Fan will cause the ALERT# pin to be
asserted.
PWM Configuration Registers
Table 5.5 PWM Configuration Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
2Ah
R/W
PWM Polarity
Config
-
-
-
-
-
-
-
POLARITY
00h
2Bh
R/W
PWM Output
Config
-
-
-
-
-
-
-
PWM_OT
00h
The PWM Config registers control the output type and polarity of all PWM outputs.
5.5.1
PWM Polarity Config - 2Ah
Bit 0 - POLARITY - Determines the polarity of the PWM.
5.5.2
„
‘0’ (default) - the Polarity of the PWM driver is normal. A drive setting of 00h will cause the output
to be set at 0% duty cycle and a drive setting of FFh will cause the output to be set at 100% duty
cycle.
„
‘1’ - The Polarity of the PWM driver is inverted. A drive setting of 00h will cause the output to be
set at 100% duty cycle and a drive setting of FFh will cause the output to be set at 0% duty cycle.
PWM Output Config - 2Bh
Bit 0 - PWM_OT - Determines the output type of the PWM driver.
„
‘0’ (default) - The PWM output is configured as an open drain output.
„
‘1’ - The PWM output is configured as a push-pull output.
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Datasheet
5.6
PWM Base Frequency Register
Table 5.6 PWM Base Frequency Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
2Dh
R/W
PWM Base
Frequency
-
-
-
-
-
-
PWM_
BASE
_1
PWM_
BASE
_0
00h
The PWM Base Frequency register determines the base frequency that is used with the PWM Divide
register to determine the final PWM frequency. The PWM frequency is set by the base frequency and
its respective divide ratio (see Section 5.8).
Controls the base frequency of the PWM driver
Bits 1-0 - PWM_BASE1[1:0] - Determines the base frequency of the PWM driver.
Table 5.7 PWM_BASEx[1:0] Bit Decode
PWM_BASEX[1:0]
5.7
1
0
BASE FREQUENCY
0
0
26.00kHz (default)
0
1
19.531kHz
1
0
4,882Hz
1
1
2,441Hz
Fan Setting Register
Table 5.8 Fan Driver Setting Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
30h
R/W
Fan Setting
128
64
32
16
8
4
2
1
00h
The Fan Setting register always displays the current setting of the fan driver. Reading from the register
will report the current fan speed setting of the fan driver regardless of the operating mode. Therefore
it is possible that reading from this register will not report data that was previously written into this
register.
While the RPM-based Fan Speed Control Algorithm is active, the register is read only. Writing to the
register will have no effect and the data will not be stored.
The contents of the register represent the weighting of each bit in determining the final output voltage.
The output drive for a PWM output is given by Equation [1].
VALUE
Drive = ⎛⎝ ---------------------⎞⎠ × 100%
255
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[1]
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
5.8
PWM Divide Register
Table 5.9 PWM Divide Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
31h
R/W
Fan Divide
128
64
32
16
8
4
2
1
01h
The PWM Divide registers determine the final frequency of the PWM Fan Driver. The driver base
frequency is divided by the value of the PWM Divide Register to determine the final frequency. The
duty cycle settings are not affected by these settings, only the final frequency of the PWM driver. A
value of 00h will be decoded as 01h.
5.9
Fan Configuration 1 Register
Table 5.10 Fan Configuration 1 Register
ADDR
R/W
REGISTER
B7
B6
32h
R/W
Fan
Configuration 1
EN_
ALGO
B5
B4
RANGE[1:0]
B3
B2
EDGES[1:0]
B1
B0
UPDATE[2:0]
DEFAULT
2Bh
The Fan Configuration 1 register controls the general operation of the RPM-based Fan Speed Control
Algorithm used for the Fan Driver.
Bit 7 - EN_ALGO - enables the RPM-based Fan Speed Control Algorithm.
„
‘0’ - (default) the control circuitry is disabled and the fan driver output is determined by the Fan
Driver Setting Register.
„
‘1’ - the control circuitry is enabled and the Fan Driver output will be automatically updated to
maintain the programmed fan speed as indicated by the TACH Target Register.
Bits 6- 5 - RANGE[1:0] - Adjusts the range of reported and programmed tachometer reading values.
The RANGE bits determine the weighting of all TACH values (including the Valid TACH Count, TACH
Target, and TACH reading) as shown in Table 5.11.
Table 5.11 Range Decode
RANGE[1:0]
1
0
REPORTED MINIMUM
RPM
TACH COUNT
MULTIPLIER
0
0
500
1
0
1
1000 (default)
2
1
0
2000
4
1
1
4000
8
Bits 4-3 - EDGES[1:0] - determines the minimum number of edges that must be detected on the
TACHx signal to determine a single rotation. A typical fan measured 5 edges (for a 2-pole fan). For
more accurate tachometer measurement, the minimum number of edges measured may be increased.
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Datasheet
Increasing the number of edges measured with respect to the number of poles of the fan will cause
the TACH Reading registers to indicate a fan speed that is higher or lower than the actual speed. In
order for the FSC Algorithm to operate correctly, the TACH Target must be updated by the user to
accommodate this shift. The Effective Tach Multiplier shown in Table 5.12 is used as a direct multiplier
term that is applied to the Actual RPM to achieve the Reported RPM. It should only be applied if the
number of edges measured does not match the number of edges expected based on the number of
poles of the fan (which is fixed for any given fan).
Contact SMSC for recommended settings when using fans with more or less than 2 poles.
Table 5.12 Minimum Edges for Fan Rotation
EDGES[1:0]
1
0
MINIMUM TACH
EDGES
NUMBER OF FAN POLES
EFFECTIVE TACH
MULTIPLIER (BASED ON 2
POLE FANS)
0
0
3
1 pole
0.5
0
1
5
2 poles (default)
1
0
7
3 poles
1.5
1
1
9
4 poles
2
1
Bit 2-0 - UPDATE[2:0] - determines the base time between fan driver updates. The Update Time, along
with the Fan Step Register, is used to control the ramp rate of the drive response to provide a cleaner
transition of the actual fan operation as the desired fan speed changes. The Update Time is set as
shown in Table 5.13.
Table 5.13 Update Time
UPDATE[2:0]
2
1
0
UPDATE TIME
0
0
0
100ms
0
0
1
200ms
0
1
0
300ms
0
1
1
400ms (default)
1
0
0
500ms
1
0
1
800ms
1
1
0
1200ms
1
1
1
1600ms
Revision 1.3 (05-18-11)
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DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
5.10
Fan Configuration 2 Register
Table 5.14 Fan Configuration 2 Register
ADDR
R/W
REGISTER
B7
B6
B5
33h
R/W
Fan
Configuration 2
-
EN_
RRC
GLITCH_
EN
B4
B3
DER_OPT [1:0]
B2
B1
ERR_RNG[1:0]
B0
DEFAULT
-
28h
The Fan Configuration 2 register controls the tachometer measurement and advanced features of the
RPM-based Fan Speed Control Algorithm.
Bit 6 - EN_RRC - Enables ramp rate control when the fan driver is operated in the Direct Setting Mode.
„
‘0’ (default) - Ramp rate control is disabled. When the fan driver is operating in Direct Setting mode,
the fan setting will instantly transition to the next programmed setting.
„
‘1’ - Ramp rate control is enabled. When the fan driver is operating in Direct Setting mode, the fan
drive setting will follow the ramp rate controls as determined by the Fan Step and Update Time
settings. The maximum fan drive setting step is capped at the Fan Step setting and is updated
based on the Update Time as given by Table 5.13.
Bit 5 - GLITCH_EN - Disables the low pass glitch filter that removes high frequency noise injected on
the TACHx pin.
„
‘0’ - The glitch filter is disabled.
„
‘1’ (default) - The glitch filter is enabled.
Bits 4 - 3 - DER_OPT[1:0] - Control some of the advanced options that affect the derivative portion of
the RPM-based Fan Speed Control Algorithm as shown in Table 5.15.
Table 5.15 Derivative Options
DER_OPT[1:0]
1
0
OPERATION
0
0
No derivative options used
0
1
Basic derivative. The derivative of the error from
the current drive setting and the target is added
to the iterative Fan Drive Register setting (in
addition to proportional and integral terms)
(default)
1
0
Step derivative. The derivative of the error from
the current drive setting and the target is added
to the iterative Fan Drive Register setting and is
not capped by the Fan Step Register.
1
1
Both the basic derivative and the step derivative
are used effectively causing the derivative term to
have double the effect of the derivative term.
Bit 2 - 1 - ERR_RNG[1:0] - Control some of the advanced options that affect the error window. When
the measured fan speed is within the programmed error window around the target speed, then the fan
drive setting is not updated. The algorithm will continue to monitor the fan speed and calculate
necessary drive setting changes based on the error; however, these changes are ignored.
SMSC EMC2301
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DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
Table 5.16 Error Range Options
ERR_RNG[1:0]
5.11
1
0
OPERATION
0
0
0 RPM (default)
0
1
50 RPM
1
0
100 RPM
1
1
200 RPM
Gain Register
Table 5.17 Gain Register
ADDR
R/W
REGISTER
B7
B6
35h
R/W
Gain Register
-
-
B5
B4
GAIND[1:0]
B3
B2
B1
GAINI[1:0]
B0
GAINP[1:0]
DEFAULT
2Ah
The Gain register stores the gain terms used by the proportional and integral portions of the RPMbased Fan Speed Control Algorithm. These gain terms are used as the KD, KI, and KP gain terms in
a classic PID control solution.
Bits 5 - 4 - GAINDX[1:0] - Controls the derivative gain term used by the FSC algorithm as shown in
Table 5.18.
Bits 3-2 - GAINIX[1:0] - Controls the integral gain term used by the FSC algorithm as shown in
Table 5.18.
Bits 1-0 - GAINP[1:0] - Controls the proportional gain term used by the FSC algorithm as shown in
Table 5.18.
Table 5.18 Gain Decode
GAIND OR GAINP OR GAINI [1:0]
1
0
RESPECTIVE GAIN FACTOR
0
0
1x
0
1
2x
1
0
4x (default)
1
1
8x
Revision 1.3 (05-18-11)
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DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
5.12
Fan Spin Up Configuration Register
Table 5.19 Fan Spin Up Configuration Register
ADDR
R/W
REGISTER
36h
R/W
Fan Spin Up
Configuration
B7
B6
DRIVE_FAIL_
CNT [1:0]
B5
B4
NOKICK
B3
B2
B1
B0
DEFAULT
SPINUP_TIME
[1:0]
SPIN_LVL[2:0]
19h
The Fan Spin Up Configuration register controls the settings of Spin Up Routine. The Fan Spin Up
Configuration register is software locked.
Bit 7 - 6 - DRIVE_FAIL_CNT[1:0] - Determines how many update cycles are used for the Drive Fail
detection function as shown in Table 5.20. This circuitry determines whether the fan can be driven to
the desired tach target.
Table 5.20 DRIVE_FAIL_CNT[1:0] Bit Decode
DRIVE_FAIL_CNT[1:0]
1
0
NUMBER OF UPDATE PERIODS
0
0
Disabled - the Drive Fail detection circuitry is disabled (default)
0
1
16 - the Drive Fail detection circuitry will count for 16 update
periods
1
0
32 - the Drive Fail detection circuitry will count for 32 update
periods
1
1
64 - the Drive Fail detection circuitry will count for 64 update
periods
Bit 5 - NOKICK - Determines if the Spin Up Routine will drive the fan to 100% duty cycle for 1/4 of the
programmed spin up time before driving it at the programmed level.
„
‘0’ (default) - The Spin Up Routine will drive the fan driver to 100% for 1/4 of the programmed spin
up time before reverting to the programmed spin level.
„
‘1’ - The Spin Up Routine will not drive the fan driver to 100%. It will set the drive at the
programmed spin level for the entire duration of the programmed spin up time.
Bits 4 - 2 - SPIN_LVL[2:0] - Determines the final drive level that is used by the Spin Up Routine as
shown in Table 5.21.
Table 5.21 Spin Level
SPIN_LVL[2:0]
2
1
0
SPIN UP DRIVE LEVEL
0
0
0
30%
0
0
1
35%
0
1
0
40%
SMSC EMC2301
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Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
Table 5.21 Spin Level (continued)
SPIN_LVL[2:0]
2
1
0
SPIN UP DRIVE LEVEL
0
1
1
45%
1
0
0
50%
1
0
1
55%
1
1
0
60% (default)
1
1
1
65%
Bit 1 -0 - SPINUP_TIME[1:0] - determines the maximum Spin Time that the Spin Up Routine will run
for (see Section 4.6). If a valid tachometer measurement is not detected before the Spin Time has
elapsed, an interrupt will be generated. When the RPM-based Fan Speed Control Algorithm is active,
the fan driver will attempt to re-start the fan immediately after the end of the last spin up attempt.
The Spin Time is set as shown in Table 5.22.
Table 5.22 Spin Time
SPINUP_TIME[1:0]
5.13
1
0
TOTAL SPIN UP TIME
0
0
250 ms
0
1
500 ms (default)
1
0
1 sec
1
1
2 sec
Fan Max Step Register
Table 5.23 Fan Max Step Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
37h
R/W
Fan Max Step
-
-
32
16
8
4
2
1
10h
The Fan Max Step register, along with the Update Time, controls the ramp rate of the fan driver
response calculated by the RPM-based Fan Speed Control Algorithm. The value of the register
represents the maximum step size the fan driver will take between update times (see Section 5.9).
When the FSC algorithm is enabled, Ramp Rate control is automatically used. When the FSC is not
active, then Ramp Rate control can be enabled by asserting the EN_RRC bit (see Section 5.10).
APPLICATION NOTE: The UPDATE bits and Fan Step Register settings operate independently of the RPM-based
Fan Speed Control Algorithm and will always limit the fan drive setting. That is, if the
programmed fan drive setting (either as determined by the RPM-based Fan Speed Control
Algorithm or by manual settings) exceeds the current fan drive setting by greater than the
Fan Step Register setting, the EMC2301 will limit the fan drive change to the value of the
Revision 1.3 (05-18-11)
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DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Fan Step Register. It will use the Update Time to determine how often to update the drive
settings.
APPLICATION NOTE: If the Fan Speed Control Algorithm is used, the default settings in the Fan Configuration 2
Register will cause the maximum fan step settings to be ignored.
The Fan Max Step register is software locked.
5.14
Fan Minimum Drive Register
Table 5.24 Minimum Fan Drive Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
38h
R/W
Fan Minimum
Drive
128
64
32
16
8
4
2
1
66h
(40%)
The Fan Minimum Drive register stores the minimum drive setting for the RPM-based Fan Speed
Control Algorithm. The RPM-based Fan Speed Control Algorithm will not drive the fan at a level lower
than the minimum drive unless the target Fan Speed is set at FFh (see Section 5.17).
During normal operation, if the fan stops for any reason (including low drive), the RPM-based Fan
Speed Control Algorithm will attempt to restart the fan. Setting the Fan Minimum Drive Register to a
setting that will maintain fan operation is a useful way to avoid potential fan oscillations as the control
circuitry attempts to drive it at a level that cannot support fan operation.
The Fan Minimum Drive Register is software locked.
5.15
Valid TACH Count Register
Table 5.25 Valid TACH Count Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
39h
R/W
Valid TACH
Count
4096
2048
1024
512
256
128
64
32
F5h
The Valid TACH Count register stores the maximum TACH Reading Register value to indicate that the
fan is spinning properly. The value is referenced at the end of the Spin Up Routine to determine if the
fan has started operating and decide if the device needs to retry. See Equation [2] in Section 5.18 for
translating the count to an RPM.
If the TACH Reading Register value exceeds the Valid TACH Count Register (indicating that the Fan
RPM is below the threshold set by this count), then a stalled fan is detected. In this condition, the
algorithm will automatically begin its Spin Up Routine.
If a TACH Target setting is set above the Valid TACH Count setting, then that setting will be ignored
and the algorithm will use the current fan drive setting.
The Valid TACH Count register is software locked.
SMSC EMC2301
35
DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
5.16
Fan Drive Fail Band Registers
Table 5.26 Fan Drive Fail Band Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
3Ah
R/W
Fan Drive
Fail Band
Low Byte
16
8
4
2
1
-
-
-
00h
3Bh
R/W
Fan Drive
Fail Band
High Byte
4096
2048
1024
512
256
128
64
32
00h
The Fan Drive Fail Band Registers store the number of tach counts used by the Fan Drive Fail
detection circuitry. This circuitry is activated when the fan drive setting high byte is at FFh. When it is
enabled, the actual measured fan speed is compared against the target fan speed. These registers
are only used when the FSC is active.
This circuitry is used to indicate that the target fan speed at full drive is higher than the fan is actually
capable of reaching. If the measured fan speed does not exceed the target fan speed minus the Fan
Drive Fail Band Register settings for a period of time longer than set by the DRIVE_FAIL_CNTx[1:0]
bits, then the DRIVE_FAIL status bit will be set and an interrupt generated.
5.17
TACH Target Registers
Table 5.27 TACH Target Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
3Ch
R/W
TACH Target
Low Byte
16
8
4
2
1
-
-
-
F8h
3Dh
R/W
TACH Target
High Byte
4096
2048
1024
512
256
128
64
32
FFh
The TACH Target Registers hold the target tachometer value that is maintained by the RPM-based
Fan Speed Control Algorithm.
The value in the TACH Target Registers will always reflect the current TACH Target value.
If the algorithm is enabled, setting the TACH Target Register to FFh will disable the fan driver (set the
fan drive setting to 0%). Setting the TACH Target to any other value (from a setting of FFh) will cause
the algorithm to invoke the Spin Up Routine after which it will function normally.
The Tach Target is not applied until the high byte is written. Once the high byte is written, the current
value of both high and low bytes will be used as the next Tach target.
Revision 1.3 (05-18-11)
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DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
5.18
TACH Reading Registers
Table 5.28 TACH Reading Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
3Eh
R
Fan TACH
4096
2048
1024
512
256
128
64
32
FFh
3Fh
R
Fan TACH
Low Byte
16
8
4
2
1
-
-
-
F8h
The TACH Reading Registers’ contents describe the current tachometer reading for the fan. By default,
the data represents the fan speed as the number of 32kHz clock periods that occur for a single
revolution of the fan.
Equation [2] shows the detailed conversion from TACH measurement (COUNT) to RPM while Equation
[3] shows the simplified translation of TACH Reading Register count to RPM assuming a 2-pole fan,
measuring 5 edges, with a frequency of 32.768kHz. These equations are solved and tabulated for ease
of use in AN17.4 RPM to TACH Counts Conversion.
Whenever the high byte register is read, the corresponding low byte data will be loaded to internal
shadow registers so that when the low byte is read, the data will always coincide with the previously
read high byte.
where:
poles = number of poles of the fan
(typically 2)
1
(n – 1)
RPM = -------------------- × ---------------------------------- × f TACH × 60
( poles )
1
COUNT × ----m
fTACH = the tachometer
measurement frequency (typically
32.768kHz)
[2]
n = number of edges measured
(typically 5 for a 2 pole fan)
m = the multiplier defined by the
RANGE bits
3,932,160 × m
RPM = -------------------------------------COUNT
5.19
[3]
COUNT = TACH Reading Register
value (in decimal)
Software Lock Register
Table 5.29 Software Lock Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
EFh
R/W
Software
Lock
-
-
-
-
-
-
-
LOCK
00h
The Software Lock Register controls the software locking of critical registers. This register is software
locked.
SMSC EMC2301
37
DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
Bit 0 - LOCK - this bit acts on all registers that are designated SWL. When this bit is set, the locked
registers become read only and cannot be updated.
5.20
„
‘0’ (default) - all SWL registers can be updated normally.
„
‘1’ - all SWL registers cannot be updated and a hard-reset is required to unlock them.
Product ID Register
Table 5.30 Product ID Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FDh
R
Product ID
0
0
1
1
0
1
1
1
37h
The Product ID Register contains a unique 8-bit word that identifies the product.
5.21
Manufacturer ID Register
Table 5.31 Manufacturer ID Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FEh
R
Manufacturer ID
0
1
0
1
1
1
0
1
5Dh
The Manufacturer ID Register contains an 8-bit word that identifies SMSC.
5.22
Revision Register
Table 5.32 Revision Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FFh
R
Revision
1
0
0
0
0
0
0
0
80h
The Revision Register contains an 8-bit word that identifies the die revision.
Revision 1.3 (05-18-11)
38
DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Chapter 6 Typical Operating Curves
The following Typical Operating Curves are included.
„
Supply Current vs. Temperature
„
Supply Current vs. Supply Voltage
„
Fan TACH Accuracy vs. Temperature
„
Fan TACH Accuracy vs. Supply Voltage
„
PWM output frequency vs. Supply Voltage
„
PWM output frequency vs. Temperature
„
FSC Operation
Supply Current vs. Supply Voltage
400
380
380
360
360
340
340
Supply Current (uA)
Supply Current (uA)
Supply Current vs. Ambient Temeperature
400
320
300
280
260
320
300
280
260
240
240
220
220
200
-50
200
2.95
0
50
Ambient Temperature (°C)
100
3.35
3.45
3.55
3.65
1
0.8
Tach
Measurement
Accuracy
(%)(%
Tach
Measurement
Accuracy
Tach Measurement
MeasurementAccuracy
Accuracy(%)
(%
Tach
3.25
Tachometer Measurement Accuracy vs. Supply Voltage
Tachometer Measurement Accuracy vs. Ambient Temperature
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
0
50
100
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
2.95
150
3.05
3.15
3.25
3.35
3.45
3.55
3.65
Supply Voltage (V)
(C)
AmbientTemperautre
Temperature (°C)
SMSC EMC2301
3.15
Supply Voltage (V)
1
-1
-50
3.05
150
39
DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
PWM Frequency vs. Ambient Temperature
V DD = 3.3V, Base Frequncy = 26Khz
PWM Frequency vs. Supply Voltage
TA = 25C, Base Frequncy = 26Khz
27000
27000
26800
26800
26600
26400
PWM Frequency (Hz)
PWM Frequency (Hz)
26600
26200
26000
25800
25600
25400
25200
26400
26200
26000
25800
25600
25400
25200
25000
-50
0
50
100
25000
2.95
150
3.05
T emp er at ur e ( C
)
Ambient Temperature
(°C)
3.15
3.25
3.35
3.45
3.55
3.65
Supply Voltage (V)
FSC Algorithm Spin Up Routine – NoKick
Spin Time = 1.0s; Spin Level = 50%; UpdateTime = 200ms;
RPM Target from 0 RPM -> 8000 RPM @ time t = 0
FSC Algorithm Spin Up Routine
Spin Time = 1.0s; Spin Level = 55%; Updated Time = 200ms;
RPM Target from 0 RPM -> 8000 RPM @ time t = 0
PWM
Output
PWM
Output
10x
Zoom on
PWM
Output
10x
Zoom on
PWM
Output
Duty Cycle Measured = 53.8%
t=0
t=0
Duty Cycle Measured = 50%
FSC Algorithm PWM Ramping
Update Time = 200ms; Max Step = 16 PWM counts
RPM Target from 0 RPM -> 8000 RPM @ time t = 0
PWM
Output
10x
Zoom on
PWM
Output
Spin Up Routine Ends – begins normal
operation
Update Time ends, PWM duty cycle changed
Revision 1.3 (05-18-11)
Duty Cycle
Measured
Update Time ends, PWM duty
cycle changed
40
DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Chapter 7 Package Drawing
7.1
EMC2301 Package Information
REVISIO N HIST ORY
REVI SION
3
D
P IN 1 IDE NTIFIER
AR EA (D /2 X E1/2)
e
3
DATE
RELEASEDBY
-
-
SEE SPEC FRONT PAGE FOR REVISI ONHISTORY
5
c
E1
2
DESCRIPTION
-
E
SEE DE TAIL "A"
8X b
TOP VIEW
END VIEW
A2
A
C
SE ATING P LANE
A1
ccc C
SIDE VIEW
3-D VIEW
1. ALL DIMENSIONS ARE IN MILLIMETER.
2. TOLERANCE ON THE TRUE POSITI ON OF THE LEADS I S ± 0.065mm MAXIMUM.
3. PACKAGE BODY DIMENSIONS "D" AND "E1" DO NOT INCLUDE MOLD PROTRUSIONS OR FLASH.
MAXIMUM MOLD PROTRUSIONS OR FLASH I S 0.15 mm (0.006 I NCHES) PER END AND SIDE.
DIMENSIONS "D" AND "E1" ARE DETERMINED AT DATUM PLANE "H".
4. DIMENSION FOR FOOT LENGTH "L" IS MEASURED AT THE GAUGE PLANE 0.25mm ABOVE THE
SEATING PLANE.
5. DETAILS OF PIN 1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE
INDICATED.
H
C
NOTES:
GA U GE PLAN E
0.2 5
S EAT IN G PLAN E
0 ° - 8°
4
L
UNLESS OTHERWISE SPECI FIED
DIMENSIONS ARE IN MILL IMETERS
AND TOLERANCES ARE:
L1
DECI MAL
X.X
±0 .1
X.XX ±0 .05
X.XXX ±0 .025
THIRD ANG L E PR OJ EC TIO N
80 ARKAY DRIVE
HAUPPAUGE, NY 11 788
USA
ANGULAR
±1°
TITLE
DETAIL "A"
NAME
DATE
S .K.ILIEV
7 /0 5/04
DIM AND TOL PER ASME Y14. 5M - 1994
M ATER IAL
SCALE: 3/1
FINISH
PACKAGE OUTLINE
8 PIN TSSOP, 3x 3 MM BO DY, 0.65 MM PITCH
DRA WN
-
CHE CKED
S .K.ILIEV
D WG N UM BER
S .K.ILIEV
R EV
MO-8-TSSOP-3x3
7 /0 5/04
APP RO VED
PRINT WIT H" SCALE TO FIT "
DO NOT SCAL E DRAWING
S CALE
7 /0 7/04
STD CO M PLIANCE
1 :1
JED EC: MO-1 87 / D
D
SH EET
1 OF 1
Figure 7.1 EMC2301 Package Drawing - 8-Pin MSOP
SMSC EMC2301
41
DATASHEET
Revision 1.3 (05-18-11)
RPM-Based PWM Fan Controller
Datasheet
7.2
Package Markings
TOP
LINE: 1-T – Device Number
LINE: 2-T Version, Revision, Country Code (VRCC)
2 3
0 1
2x 1.5pt
1 R C C
e3
PB-FREE/GREEN SYMBOL
(Matte Sn)
ALL TOP LINES CENTER
HORIZONTAL ALIGNMENT
PIN 1
BOTTOM
PIN 1
LINE: 1-B – Date Code (YYWW)
Y Y WW
LINE: 2-B – First 3 Digits of Lot Number
1 2 3
LINE: 3-B – Last 4 Digits of Lot Number
4 5 6 a
3x 1.5pt
Figure 7.2 EMC2301 Package Markings
Revision 1.3 (05-18-11)
42
DATASHEET
SMSC EMC2301
RPM-Based PWM Fan Controller
Datasheet
Chapter 8 Datasheet Revision History
Table 8.1 Customer Revision History
REVISION LEVEL & DATE
Rev. 1.3 (05-18-11)
SECTION/FIGURE/ENTRY
CORRECTION
Section 4.8, "Watchdog
Timer"
The ALERT# pin is asserted when the watchdog is
triggered.
Section 5.2, "Configuration
Register"
Corrected description for MASK bit. Changed “If
any bit in either status register is set, the ALERT#
pins will be asserted (unless individually masked
via the Mask Register)” to “If any bit in the status
registers is set, the ALERT# pin will be asserted
(unless individually masked via the Fan Interrupt
Enable Register)”.
Rev. 1.2 (03-22-10)
Table 2.3, "SMBus Electrical
Specifications"
Updated SMBus Data Hold Time spec to 0 us
Rev. 1.1 (10-12-09)
Table 2.2, "Electrical
Specifications"
Tachometer Setting Accuracy max was changed
from +/-3% to +/-2%.
Chapter 6, Typical
Operating Curves
Added typical operating curves
Rev. 1.0 (05-15-09)
SMSC EMC2301
Initial release of datasheet
43
DATASHEET
Revision 1.3 (05-18-11)