Diodes AM4964 - Manual (Page 9)

AM4964
Document number: DS37241 Rev. 2 - 2
9 of 21
www.diodes.com
June 2014
© Diodes Incorporated
AM4964
A Product Line of
Diodes Incorporated
N
E
W
P
R
O
D
U
C
T
Functional Descriptions
(cont.)
CF –CF Capacitor Pin
A capacitor is connected to this pin as a filter to translate PWM signal to be stable voltage. The resistors R3 and R4 are connected to CF pin to
adjust the maximum speed at high temperature and low temperature corners.
Adjust the maximum speed vs. input duty to approximately match the target specification using R3 and R4 at low temperature (T
Measure the fan rotating speed vs. input duty. And draw a curve figure accordingly (Step=5%).
Output PWM Duty vs. R3 and R4 at Low Temperature
Adjust the maximum speed vs. input PWM duty to approximately match the target specification using R3 and R4 at high temperature (T>TH,
V8>V7+0.7V).
Output PWM Duty vs. R3 and R4 at High Temperature
0 20 40 60 80 100
0
20
40
60
80
100
R3=360K 
R3=1M 
R3 open
O
u
tp
u
t
D
u
ty
(%
)
Input Duty (%)
0 20 40 60 80 100
0
20
40
60
80
100
R4=150K 
R4=390K 
R4 open
O
u
tp
u
t
D
u
ty
(%
)
Input Duty (%)
0 20 40 60 80 100
0
20
40
60
80
100
R3=360K 
R3=1M 
R3 open
O
u
tp
u
t
D
u
ty
(%
)
Input Duty (%)
0 20 40 60 80 100
0
20
40
60
80
100
R4=150K 
R4=390K 
R4 open
O
u
tp
u
t
D
u
ty
(%
)
Input Duty (%)