Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF HTML

TC654 Datasheet(PDF) 27 Page - Microchip Technology

Part No. TC654
Description  Dual SMBus™ PWM Fan Speed Controllers With Fan Fault Detection
Download  38 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  MICROCHIP [Microchip Technology]
Homepage  http://www.microchip.com
Logo 

TC654 Datasheet(HTML) 27 Page - Microchip Technology

Zoom Inzoom in Zoom Outzoom out
 27 / 38 page
background image
 2002-2014 Microchip Technology Inc.
DS20001734C-page 27
TC654/TC655
which is caused by the fan's "extra" current pulse
during PWM output turn-on.
FIGURE 7-10:
Extra Pulse at Sense Pin.
This problem occurs mainly with fans that have a cur-
rent waveshape like the one shown in Figure 7-9. For
configurations where an NPN transistor is being used
as the external drive device, the typical RSENSE and
CSENSE scheme can continue to be used to sense the
fan current pulses. In order to eliminate the extra cur-
rent pulse, a slow-down capacitor can be placed from
the base of the transistor to ground. A 0.1 µF capacitor
is appropriate in most cases. This arrangement is
shown in Figure 7-11. This capacitor will help to slow
down the turn-on edge of the transistor and reduce the
amplitude of the extra current pulse.
For configurations using an N-channel MOSFET as the
drive device, the slow-down capacitor does not fix all
conditions and the current sensing scheme must be
changed. Since the current for this type of fan always
returns to zero, the coupling capacitor (CSENSE) is not
needed. Instead, it will be replaced by an R-C configu-
ration to eliminate the voltage pulse generated by the
extra current pulse. This new sensing configuration is
shown in Figure 7-12. The values of the resistor/capac-
itor combination should be adjusted so that the voltage
pulse generated by the extra current pulse is smoothed
and is not registered by the TC654/TC655 as a true fan
current pulse. Typical values for RSLOW and CSLOW are
1K
 and 1000 pF, respectively.
FIGURE 7-11:
Transistor Drive with CSLOW
Capacitor.
FIGURE 7-12:
FET Drive with RSLOW/
CSLOW Sense Scheme.
Sense Pin Voltage
"Extra Pulse"
VOUT PWM
FAN
FAN
RISO1
RISO2
CSENSE
12
(0.1 µF typical)
SENSE2
SENSE1
VOUT
TC654/
TC655
(0.1 µF typical)
CSLOW1
(0.1uF
GND
typical)
(0.1 µF typical)
RSENSE2
CSENSE2
RSENSE1
CSLOW2
FAN
FAN
RSLOW2
RSLOW1
RSENSE2
RSENSE1
CSLOW1
1
2
(1000pF typical)
SENSE2
SENSE1
VOUT
TC654/
TC655
CSLOW2
(1000pF typical)
GND
(1 k
 typical)
(1 k
 typical)


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 


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