as1720 austriamicrosystems, as1720 Datasheet - Page 7

• Manufacturer Part Number: as1720
• Description: Solenoid / Valve Driver With Current Limitation
• Manufacturer: austriamicrosystems

AS1720
Datasheet - D e t a i l e d D e s c r i p t i o n
www.austriamicrosystems.com
Control by pin ENN
When VDDHV is constantly switched on the AS1720 can be controlled by pin ENN. The functionality is the same as for
controlling the device via pin VDDHV. This feature is useful when controlling by a microprocessor is desired.
Because of the internal pull-up resistor to V
can be used.
Current Adjust (AS1720A) and Current Limitation (AS1720B)
This block provides the current reference for the output current source. The current is generated by regulating the
internal Bandgap voltage to the pins IE and IH. The external resistors R
expressed as:
The temperature coefficient depends on the Bandgap voltage (100ppm/K, box method) and external resistor (in the
range of several ppm/K).
The saturation voltage of the output current source for a 100mA current is typical 600mV.
Figure 10. Simplified Circuit of Blocks Current Adjust and Current Source
1.2V reference
R
IE
IE
DDA
R
IH
a microprocessor with open-drain or with push/pull (max 3.3V) output
1.2V
Current mirror
R
IH
Revision 1.03
IE IH
⁄
PWM & Control
=
----------- -
I
OUT
k
IE
and R
IH
define the output current and can be
OUT
(EQ 2)
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