AT5560
Preliminary Product Information
VCM Driver for Mobile Phone
The following diagrams show the characteristic curve for the voltage at IM pin vs. duty ratio of PWM
signal and output current vs. duty ratio of PWM signal.
At this example, the PWM frequency is 20KHz, the sense resistance, RNF=1.5
Ω
, and the R1=13K
Ω
,
R2=20K
Ω
, and C1=0.1uF are set in front of IN pin respectively. Above settings can make AT5560 output
90mA when duty ratio of PWM signal is 80%.
From result, the correlation of output current and duty ratio of PWM signal is highly linear.
IN pin voltage vs. duty ratio of PWM
VCC=2.8V
1.6
1.4
1.2
100.0
90.0
80.0
Output current vs. duty ratio of PWM
VCC=2.8V
Output current (mA)
IN pin voltage (V)
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
PWM 20KHz
1.0
0.8
0.6
0.4
0.2
0.0
0
20
40
60
80
100
PWM 20KHz
0
20
40
60
80
100
Duty ratio of PWM (%)
Duty ratio of PWM (%)
The smaller value of sense resistance, RNF, will cause lesser voltage variation at voltage IM pin. The
accuracy of output current is closely dependent on voltage at IM pin. Another reason choosing smaller
value of RNF is that the decreasing voltage drop at IM pin can crease the maximum output driving current
when the PVCC is fixed. So RNF=1.5
Ω
is the better choice.
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW:
http://www.aimtron.com.tw
2006/08/24 REV:0.4
Email:
service@aimtron.com.tw
7
AIMTRON [ AIMTRON TECHNOLOGY ]
