AS1720 查看數據表（PDF） - austriamicrosystems AG

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AS1720

Solenoid / Valve Driver with Current Limitation

austriamicrosystems AG 

AS1720

Datasheet - Detailed Description

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 VDDA a microprocessor with open-drain or with push/pull (max 3.3V) output 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 RIE and RIH define the output current and can be expressed as:

RIE ⁄ IH

=

-----k------

IOUT

(EQ 2)

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

Current mirror

OUT

1.2V

PWM & Control

IE

IH

RIE

RIH

www.austriamicrosystems.com/Solenoid-Relay-Driver/AS1720 Revision 1.04

7 - 12

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