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

8 Detailed Description

Delay

The delay time is generated internally by a digital divider.

LDO and Reference Generator

This block provides the internal supply voltage of typ. 3.3V and all bias currents for the analog cells. Further the external resistor divider for

setting the duty cycle will be supplied.

Thermal shutdown

The temperature is constantly monitored. If the temperature exceeds typ. 160ºC the output is disabled. In order to exit the over temperature

condition, the device has to cool down and the reason of over temperature (e.g. short circuit) must be removed. After exiting the overtemperature

condition the system restarts beginning with the energizing phase followed by the hold phase.

DC Operation (AS1720A only)

After power up, the delay time (see Delay) starts running. After expiration of the delay the hold phase starts automatically. During the hold phase

the DC output current is reduced according to the RIH on pin IH.

PWM Operation (AS1720B only)

After power up, the delay time (see Delay) starts running. After expiration of the delay the hold phase starts automatically. The internal RC

oscillator sets the PWM period. The duty cycle is either defined by the external resistor divider (voltage) at pin DUTY or by the fixed internal

divider. When using the external divider the duty cycle can be adjusted between 20% and 90% (e.g. from a DAC). Alternatively the pin can be

driven by a voltage source. For using the internal divider the pin DUTY has to be connected to VDDA. The comparator recognizes this condition

and switches to the internal divider, which causes a fixed 50% duty cycle.

DUTYCYCLE(VDUTY) = 0, 381 × VDUTY – 0, 014

(EQ 1)

Figure 9. Simplified Circuit of Block PWM and Control

VDDA

R1

adjustable

Duty cycle

DUTY

R2

Vref

optional

fixed

VDDA

50% Duty cycle

DUTY

Internal VDDA typ. 3.3V

30kHz

Oscillator

Delay

PWM &

Control

VDDA

RPU

ENN

Off

On

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

6 - 12

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