MD215 SITI [Silicon Touch Technology Inc.], MD215 Datasheet - Page 6

• Manufacturer Part Number: MD215
• Description: VCM Driver for Mobile Phone
• Manufacturer: SITI [Silicon Touch Technology Inc.]

Application Notes
SP-MD215-A.001
The 11-MD215 is constant current control for use in Auto-Focus. The range of
supply voltage of 11-MD215, VDD is from 2.0V to 5.5V. The 11-MD215 digital
control pin, PD, its input range is defined that logic “H” is from 0.57*VDD to
VDD+0.4V and logic “L” is from –0.4V to 0.2*VDD. So the digital PD pin is
suitable to be controlled by 1.8V ISP.
The power down pin (PD) is the enable pin of 11-MD215, which logic high level
(PD = H) is for IC operation. On the other hand, its logic low level (PD = L) puts
the chip into standby mode for power saving. Internal pull low resistor, 300k,
prevents IC from abnormal operation when PD is open. Therefore, it is easy to
switch the working status by controlling PD pin, and it is recommended that keeps
PD at low level (PD = L) before operation to reach the maximum efficiency of
power saving, especially in the application of portable device.
Constant current operation of 11-MD215 provides the current, which can be
evaluated by the formula
current by controlling input dc voltage, V
of R
suitable and stable input voltage level, V
output.
In the application circuit diagram, the signal PWM, V
filter which consists of R
given by
, which D% is the duty ratio of PWM frequency. The corresponding of constant
current at the output could be changed by setting different duty ratio of PWM, In
order to confirm the accuracy and stable value of constant current, the amount of
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
A
, R
B
, and the capacitance C
V
ω
IN
Version
A
3
I =
dB
, R
=
=
R
V
15
B
(
A
IN
, and C
R
R
+
IN
B
A
：
R
, with appropriately PWM frequency will get the
//
( )
A.001
B
A
R C
1
D
B
%
. It is convenient to get constant output
)
IN
IN
×
. The -3dB frequency
IN
. Therefore, by adjusting the resistance
V
IN
PWM
, for setting constant current in the
( )
V
,
PWM
, is filtered by a low pass
ω
3dB
and V
Page
：
IN
5
are
(1)