D ata sh eet
A S1 7 2 0
S o l en o id / Va lv e D r iv e r w i th Cu r r e n t L im it at io n
1 General Description
2 Key Features
The AS1720A is a low side current source providing an optimized
DC Operation for power saving and ultra low electromagnetic
radiation.
The AS1720B is a low side switch providing a PWM output, which
frequency is defined by an internal RC oscillator. The adjustable
PWM allows a fine control of the power delivered to the load.
Table 1. Standard Products
Model
Operation Mode
AS1720A
DC Current Source Operation
AS1720B
PWM Switching Operation
Supply Range: +5V to +50V
Internal VDDA: 3.3V
Supply Current: 1 mA
Internal osc frequency: 30kHz
Fix delay: 136ms
Adjustable duty cycle: 20% – 90% (AS1720B only)
Adjustable energizing current: 10mA – 100mA
Adjustable hold current: 30% - 70% of energizing current
Current Limitation
Thermal shutdown: 150ºC
8-pin MLPD (2x2mm) Package
On request SOIC 8 Package (reduced temperature range -40°C
to +85°C)
The AS1720A and AS1720B can be set to provide a strong initial
closure current and is automatically switching to hold mode for
power saving. The initial DC current, the hold current and the duty
cycle of the PWM can be adjusted by external resistors. An internal
thermal sensor prevents damage of the circuit due to excessive
heating up.
3 Applications
Both devices are optimized for driving electromechanical devices
such as valves, solenoids relays, actuators and positioners.
The AS1720 is ideal for fluid and gas flow systems, industrial control,
electrical heaters, motor speed control.
Figure 1. AS1720 - Block Diagram
Vsupply: +5V to +50V
Internal VDDA typ. 3.3V
1
100nF
LDO &
Ref Generator
VDDHV
AS1720
2
VDDA
30kHz
Oscillator
Delay
R1
adjustable
Duty cycle
R2
Thermal
Shutdown
3
PWM &
Control
DUTY
L
RL
FreeWheeling
Diode
4
OUT
10nF
Current
Adjust
Vref
VDDA
5
RPU
VSS
ENN
8
IE
Off
On
IH
6
RIE
Energising Current adjust
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7
RIH
Hold Current adjust
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AS1720
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Out (Top View)
8 ENN
VDDHV 1
VDDA 2
AS1720
DUTY 3
OUT 4
7 IH
6 IE
5 VSS
Pin Description
Table 2. Pin Descriptions
Pin Name
VDDHV
VDDA
Pin Number
1
2
DUTY
3
OUT
VSS
IE
IH
4
5
6
7
ENN
8
Description
Positive supply voltage
Internal supply of 3.3V (typ.)
Duty-Cycle. By means of this pin the duty cycle can be adjusted between 20% and 90% during hold
phase. The duty cycle can be adjusted by a voltage source or an external resistor divider. Setting this
pin to VDDA the 50% duty cycle is selected automatically.
Current Source Output
Ground
Energize Current. This pin defines the current during energize phase by means of a resistor.
Hold Current. This pin defines the current during hold phase by means of a resistor.
Enable Not. This pin can be used to switch on/off the current source (e.g. via a µP), when the
AS1720 is always powered on.
Low during start-up: When VDDHV is applied, the device starts with the energise phase, followed by
the hold phase.
When the device is constantly powered on, it can be controlled by this pin.
High: The output current source is switched off.
Low: The device starts with the energise phase, followed by the hold phase.
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AS1720
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in Table 3 may cause permanent damage to the device. These are stress ratings only, and functional operation of
the device at these or any other conditions beyond those indicated in Section 6 Electrical Characteristics on page 4 is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Table 3. Absolute Maximum Ratings
Parameter
Min
Max
Units
Notes
VDDHV, OUT
-0.9
+55
V
VDDA, DUTY, ENN, IE, IH
-0.3
+5
V
Input Current (latch-up immunity)
-100
100
mA
Norm: JEDEC 78 @85°C
+/- 1.5
kV
Norm: MIL 883 E method 3015
Thermal Resistance θJA
+36
ºC/W
Junction Temperature TJ
+140
ºC
Electrical Parameters
Electrostatic Discharge
Electrostatic Discharge HBM
Temperature Ranges and Storage Conditions
Storage Temperature Range
-55
Package Body Temperature
Humidity
+150
+260
5
Moisture Sensitive Level
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85
1
Internally limited
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with IPC/
JEDEC J-STD-020 “Moisture/Reflow Sensitivity
Classification for Non-Hermetic Solid State
Surface Mount Devices”.
The lead finish for Pb-free leaded packages is
matte tin (100% Sn).
%
Non-condensing
Represents a max. floor life time of unlimited
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AS1720
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
VDDHV = 5V, VSS = 0V, Typical Values are at TAMB = +25ºC (unless otherwise specified). All limits are guaranteed. The parameters with min
and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods.
Table 4. Electrical Characteristics
Symbol
Parameter
Conditions
TAMB
Operating Ambient Temperature
TJ
Operating Junction Temperature
Min
Typ
Max
Units
-40
+85
°C
-40
+125
°C
5
50
V
3.3
3.5
V
1
2
mA
10
100
mA
2
VDDA
VSS
1.2
valid for AS1720A & AS1720B
VDDHV
Supply Voltage Range
VDDA
Internal Supply
IDD
Supply Current
IOUT_E
Output Energizing Current Range
defined by RIE
(see Figure 10 on page 7)
Digital Input Threshold
@ pin ENN
VHYST
Hysteresis
@ pin ENN
200
mV
RPU
Pull-Up Resistor
@ pin ENN
100
kΩ
Delay Time
See Delay on page 6
136
ms
VIH
VIL
no load
1
3.1
V
TSHDN
Thermal Shutdown Temperature
160
ºC
∆TSHDN
Thermal Shutdown Hysteresis
15
ºC
only valid for AS1720A
1
VOUT
Saturation Voltage, Sink
k
Transfer Value
IOUT_H
Output Hold Current Range
IOUT = 100mA
RIE = 12kΩ, VDDHV = 5V to 50V, OUT =
1V to 40V (see page 7)
1080
defined by RIH
(see Figure 10 on page 7)
0.3 x
IOUT_E
1
0.6
1
V
1200
1320
AΩ
0.7 x
IOUT_E
mA
only valid for AS1720B
Minimum Duty Cycle
15
20
25
%
Maximum Duty Cycle
83
90
95
%
Internal Duty Cycle
Vtrig
Trigger level to select internal
voltage divider
fPWM
PWM Frequency
@ pin DUTY
25.5
50
%
VDDA
V
30
34.5
kHz
1. The parameters are tested with proprietary test modes.
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AS1720
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
VSUPPLY = 5V, RIE = 30kΩ, RIH = 120kΩ, TAMB = +25ºC (unless otherwise specified);
Figure 3. Duty Cycle vs. VDUTY
Figure 4. PWM Frequency vs. Temperature
90
35
34
PWM Frequency (kHz)
Duty Cycle (%)
80
70
60
50
40
30
33
32
31
30
29
28
27
26
20
0.5
0.75
1
1.25
1.5
1.75
2
2.25
25
-40
2.5
-20
0
20
Voltage @ pin DUTY (V)
40
60
80
100 120
Temperature (°C)
Figure 5. Supply Current vs. Supply Voltage
Figure 6. Supply Current vs. Temperature
440
550
430
500
410
IDD (µA)
IDD (µA)
420
400
390
380
450
400
350
370
360
5
10
15
20
25
30
35
40
45
300
-40
50
-20
0
VDDHV (V)
Figure 7. Transfer Function vs. Supply Voltage
40
60
80
100 120
Figure 8. Transfer Function vs. Temperature
1400
1400
1350
1350
1300
1300
Transfer Value k
Transfer Value k
20
Temperature (°C)
1250
1200
1150
1100
1250
1200
1150
1100
1050
5
10
15
20
25
30
35
40
1050
-40 -20
VDDHV (V)
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0
20
40
60
80
100 120
Temperature (°C)
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AS1720
Datasheet - D e t a i l e d D e s c r i p t i o n
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 ( V DUTY ) = 0, 381 × V DUTY – 0, 014
(EQ 1)
Figure 9. Simplified Circuit of Block PWM and Control
Internal VDDA typ. 3.3V
VDDA
30kHz
Oscillator
Delay
R1
DUTY
adjustable
Duty cycle
R2
PWM &
Control
Vref
VDDA
optional
fixed
50% Duty cycle
VDDA
DUTY
RPU
ENN
Off
On
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AS1720
Datasheet - D e t a i l e d D e s c r i p t i o n
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:
k
R IE ⁄ IH = -----------(EQ 2)
I OUT
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
OUT
Current mirror
1.2V reference
1.2V
PWM & Control
IH
IE
RIE
RIH
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AS1720
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
In order to drive relays, which need more than 100mA current, an external circuitry (see Figure 11) can be used. This application shows how to
drive 5W @12V relays.
This circuit is only applicable for AS1720A.
For this example with R1 = 100Ω and RS = 2.5Ω the current Is is calculated as follows:
R1
100
I S = I 1 × ------ = 0, 01A × --------- = 400mA
RS
2, 5
(EQ 3)
Figure 11. AS1720A - Typical Application
Vsupply: +12V
IS
R1
100Ω
VDDHV
1V
RS
100nF
VDDA
I1
AS1720A
DUTY
OUT
+
LM741
10mA
Relay
BC161
FreeWheeling
Diode
VSS
ENN
IE
IH
RIE
RIH
120kΩ
Energising Current adjust
240kΩ
Hold Current adjust
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AS1720
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
10 Package Drawings and Markings
Figure 12. 8-pin MLPD (2x2mm) Marking
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AS1720
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
Figure 13. 8-pin MLPD (2x2mm) Package
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AS1720
Datasheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The device is available as the standard products shown in Table 5.
Table 5. Ordering Information
Ordering Code
Marking
Description
Delivery Form
Package
AS1720A-ATDT
A0
Solenoid / Valve Driver with Current Limitation and with
DC Current Source Operation
Tape and Reel
8-pin MLPD (2x2mm)
AS1720B-ATDT
AW
Solenoid / Valve Driver with Current Limitation and with
PWM Switching Operation
Tape and Reel
8-pin MLPD (2x2mm)
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AS1720
Datasheet
Copyrights
Copyright © 1997-2011, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®.
All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of
the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the
freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at
any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for
current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range,
unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for each application. For shipments of less than 100 parts the
manufacturing flow might show deviations from the standard production flow, such as test flow or test location.
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