AS1920, AS1922 D a ta S h e e t Tr i p l e - Vo l ta g e , M i c r o - P o w e r M i c r o p r o c e s s o r Supervi s ory Ci rcuits 1 General Description 2 Key Features The AS1920 and AS1922 microprocessor supervisory circuits were designed to generate a reset when at least one of the three monitored supply voltages falls below its respective trip threshold. These very-low-current (6.2µA, typ) devices maintain reset for a minimum timeout period after all supplies have stabilized. Guaranteed to be in the correct state for VCC > +1.0V, these devices are perfect for multiple-voltage systems with low current requirements and strict monitoring requirements. The devices are available as the standard products listed in Table 1. Table 1. Standard Products Model Output Type Supervisory Voltages AS1920-18 Push/Pull 3V, 1.8V, Adjustable AS1922-18 Open-Drain 3V, 1.8V, Adjustable All devices monitor primary and secondary factorytrimmed voltages. Additionally, a third monitoring voltage can be selected via an external resistor divider. The AS1920 has an active-low push/pull reset output, whereas the AS1922 has an active-low open-drain reset output. ! Simultaneous Triple-Voltage Monitoring ! Very-Low Supply Current: 6.2µA ! ±1.5% Accuracy Over Temperature ! Reset Time Delay: 200ms ! Power Supply Transient Immunity ! Guaranteed Reset for VCC3 ≥ 1V or VCC18 ≥ 1V ! Active-Low Push/Pull Reset Output (AS1920) ! Active-Low Open-Drain Reset Output (AS1922) ! 5-pin SOT23 Package 3 Applications The AS1920 and AS1922 are available in a 5-pin SOT23 package. The devices are ideal for personal computers, notebooks, battery-powered systems, embedded controllers, intelligent instruments, automotive systems, critical CPU monitoring, and any multi-supply monitoring application. Figure 1. Typical Application Diagram 3V System Logic 1.8V 2.5V 5 VCC3 4 0.1µF www.austriamicrosystems.com R1 130kΩ 1% 0.1µF R2 100kΩ 1% VCC18 AS1920/ AS1922 3 VCCA Revision 1.00 1 RESETN 2 GND 1 - 14 AS1920/AS1922 Datasheet - P i n o u t 4 Pinout Pin Assignments Figure 2. Pin Assignments (Top View) RESETN 1 GND 2 5 VCC3 AS1920/ AS1922 VCCA 3 4 VCC18 Pin Descriptions Table 2. Pin Descriptions Pin Number Pin Name Description 1 RESETN Reset Logic Output. This active-low pin serves as the 3V push/pull reset output. A reset is asserted when any one of the supplies are below its respective trip threshold and the reset is held for 200ms after all power supplies have stabilized. 2 GND Ground. 3 VCCA VCCA. 1V sense, high-impedance input. Note: If this pin is not used it should be tied to VCC3 or VCC18. 4 VCC18 VCC18. 1.8V sense input and power detect pin (AS1920-18, AS1922-18). This pin provides power to the output reset stage of the device in order to assert a valid reset when the voltage on the primary input is down. Note: Bypass this pin to GND with a ≥0.1µF ceramic capacitor. 5 VCC3 VCC3. 3V sense input and power supply pin (AS1920-18, AS1922-18). This pin provides power to the device. Note: Bypass this pin to GND with a ≥0.1µF ceramic capacitor. www.austriamicrosystems.com Revision 1.00 2 - 14 AS1920/AS1922 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 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 VCC18, VCC3, VCCA to GND -0.3V +5 V RESETN Open-Drain -0.3 +7 V RESETN to GND -0.3 VCC3 + 0.3 V Operating Temperature Range -40 +85 ºC Storage Temperature Range -65 +150 ºC Package Body Temperature www.austriamicrosystems.com +260 ºC Revision 1.00 Comments Guaranteed to meet specified performance from 0 to 70ºC and is designed, characterized and assured to meet the extended temperature limits of -40 to 85ºC but are not tested at these temperatures. The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/JEDEC J-STD-020C “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). 3 - 14 AS1920/AS1922 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 VCC18 = 1.8V, VCC3 = 3V, VCCA = VCC3, TAMB = -40 to +85ºC (unless otherwise specified). Table 4. Electrical Characteristics Symbol Parameter VRT18 Min Typ Max Unit Reset Threshold VCC18 1.653 1.683 1.713 V VRT3 Reset Threshold VCC3 2.763 2.805 2.847 V VRTA Reset Threshold VCCA 0.982 1.00 1.018 V VCC3, VCC18 Operating Voltage RESETN in Correct Logic State 3.3 V IVCC18 VCC18 Supply Current VCC18 < VCC3, VCC18 = 1.8V 0.7 2 µA IVCC3 VCC3 Supply Current VCC18 < VCC3, VCC3 = 3V 6.2 15 µA VCCA Input Current VCCA = 1V -15 0 15 nA IOUT Open-Drain RESETN Output Current Reset Not Asserted, Forced to 0V 2 4 13 µA ILEAK Open-Drain RESETN Output Leakage Current Reset Not Asserted, RESETN Forced to 5.5V, TAMB = 25ºC -0.1 0.1 µA tRST Reset Pulse Width RESETN Low, TAMB = 25ºC 2 140 280 ms tUV VCC Undervoltage Detect to RESETN VCC18, VCC3, or VCCA < 2 Reset Threshold by > 1% TAMB = 25ºC 130 ISINK = 2.5mA, VCC3 = 3V, VCC18 = 0V 0.15 0.4 ISINK = 100µA, VCC3 = 1V, VCC18 = 0V 0.05 0.3 ISINK = 100µA, VCC3 = 0V, VCC18 = 1V 0.05 0.3 ISINK = 100µA, VCC3 = 1V, VCC18 = 1V 0.05 0.3 IVCCA VOL VOH 1 Output Voltage Low, RESETN Output Voltage High, RESETN Conditions ISOURCE = 1µA (AS1922-xx) 1 200 µs V VCC3 1 VCC3 0.65 V 1. Guaranteed by design. 2. Measured from the time (t1) when the input passes through the input threshold voltage (VRTX) to the time (t2) when RESETN passes through 1.5V. www.austriamicrosystems.com Revision 1.00 4 - 14 AS1920/AS1922 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 TAMB = +25ºC (unless otherwise specified). Figure 3. IVCC18 vs. Temperature Figure 4. IVCC3 vs. Temperature; VCC3 = 3V 6.5 6.4 VCC3 Supply Current (µA) e VCC18 Supply Current (µA) e 1 0.9 0.8 0.7 0.6 0.5 -100 -50 0 50 6.3 6.2 6.1 6 5.9 5.8 5.7 5.6 5.5 -100 100 Temperature (°C) 0 50 100 Temperature (°C) Figure 5. Supply Current VCCA vs. Temperature Figure 6. VOH/RST vs. Temperature; VCC3 = 3V 10 2.5 9 2.45 8 Output Voltage High e VCCA Supply Current (nA) e -50 7 6 5 4 3 2 2.4 2.35 2.3 2.25 1 0 -100 -50 0 50 2.2 -100 100 -50 Temperature (°C) 100 Figure 8. tUV vs. Temperature; VCC3 = VCCA = 3V 280 150 VCC Undervoltage Detect [µs] e Reset Pulse Width (ms) e 50 Temperature (°C) Figure 7. tRST vs. Temperature; VCC3 = VCCA = 3V 260 240 220 200 180 160 140 -100 0 -50 0 50 100 125 100 75 50 -100 0 50 100 Temperature (°C) Temperature (°C) www.austriamicrosystems.com -50 Revision 1.00 5 - 14 AS1920/AS1922 Datasheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description The AS1920/AS1922 microprocessor supervisory circuits were designed to generate a reset when at least one of the three monitored supply voltages falls below its respective trip threshold. These very-low-current (6.5µA, typ) devices maintain reset for a minimum timeout period after all supplies have stabilized. Guaranteed to be in the correct state for VCC > +1.0V, these devices are perfect for multiple-voltage systems with low current requirements and strict monitoring requirements. Figure 9. AS1920 Block Diagram 5 – VCC3 Power Detect VCC Internal + VCC3 4 VCC18 200ms Pulse Generator – 1 RESETN 200ms Delay + 3 – VCCA + 2 AS1920 Bandgap Reference GND Figure 10. VCC Monitor Timing Diagram VCCX VRTX tRST tUV RESETN www.austriamicrosystems.com 1.5V Revision 1.00 6 - 14 AS1920/AS1922 Datasheet - D e t a i l e d D e s c r i p t i o n Figure 11. AS1922 Block Diagram 5 – VCC3 Power Detect VCC Internal + VCC3 4 IOUT VCC18 200ms Pulse Generator – 1 RESETN 200ms Delay + 3 – VCCA + 2 GND www.austriamicrosystems.com Bandgap Reference Revision 1.00 AS1922 7 - 14 AS1920/AS1922 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 Supply Monitoring The AS1920/AS1922 are low-power, high-accuracy triple-supply monitoring circuits with a single 200ms microprocessor reset output. All VCC inputs (VCC18, VCC3, and VCCA) must be above their thresholds to prevent a reset from being asserted. The AS1920/AS1922 will assert a reset during powerup, powerdown and brownout conditions on one or all of the VCC inputs. Power Detect The AS1920/AS1922 is powered from the 3V input pin (VCC3). The power detect circuitry ensures that the device pulls pin RESETN low as soon as the primary input pin is ≥1V or the secondary input pin is ≥1V. Powerup The power detect circuitry ensures that RESETN will be low when either VCC18 or VCC3 ≥1V. As long as any one of the VCC inputs is below its reset threshold, RESETN will stay at a logic low. When all VCC inputs have stabilized, an internal timer will be started and RESETN will be driven high after 200ms. Powerdown On powerdown, if any of the VCC inputs drop below its threshold, RESETN is held at a logic low (0.3V) and is guaranteed until VCC3 and VCC18 < 1V. Override Functions As the trip points for VCC3 and VCC18 will always be greater than the trip point for VCCA, if pin VCCA is not used, it should be tied to VCC3 or VCC18. In a similar manner if pin VCC18 is not used it should be tied to VCC3. Tying VCC3 to VCC18 and operating from a 1.8V supply will assure the continuous assertion of RESETN. Note: Pin VCC3 must be used in all configurations. Ensuring RESETN Valid for Supply Voltages < 1V When the supplies drops below 1V the RESETN output current sink capability is greatly reduced. Stray currents and stray capacitance to signals other than GND can cause the RESETN output to float. This is not relevant for most applications since most microprocessors and other circuits do not operate with a supply voltage < 1V. In applications where the RESETN output must be valid down to 0V, a pulldown resistor from pin RESETN to ground will ensure RESETN is held low (see Figure 12). Figure 12. Typical Application w/Resistor on RESETN Output to GND 5 3V VCC3 1.8V Adjustable Supply 4 VCC18 AS1920/ AS1922 3 R1 1 RESETN 2 VCCA R3 100kΩ GND R2 The value of the pulldown resistor (R3) is a trade-off between pulldown strength and loading of the RESETN pin. If the value of R3 is too large RESETN may still float, and if the value of R3 is too small it may load RESETN and also use excess supply current, therefore a value of 100kΩ is recommended for the pulldown resistor. www.austriamicrosystems.com Revision 1.00 8 - 14 AS1920/AS1922 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Figure 13. Triple-Supply Monitor (3V, 1.8V, Adjustable) 5 3V RESETN System Reset 4 1.8V VCC18 Adjustable Supply or DC/DC Feedback Divider 1 VCC3 AS1920-18 3 2 VCCA R1 GND R2 To ensure threshold accuracy, set the parallel combination of R1 and R2 ≤ 66.5kΩ Figure 14. Dual-Supply Monitor (3V and 1.8V; Disable VCCA Input) 5 3V 1 VCC3 RESETN System Reset 4 1.8V VCC18 AS1920-18 3 2 VCCA GND Figure 15. Dual-Supply Monitor (3V and Adjustable) 3V 5 1 RESETN VCC3 System Reset 4 VCC18 Adjustable Supply or DC/DC Feedback Divider To ensure threshold accuracy, set the parallel combination of R1 and R2 ≤ 66.5kΩ www.austriamicrosystems.com AS1920-18 3 VCCA R1 2 GND R2 Revision 1.00 9 - 14 AS1920/AS1922 Datasheet - A p p l i c a t i o n I n f o r m a t i o n Figure 16. VCCA Tied to DC/DC Feedback Divider 2.5V 27.4kΩ 1% 5 3V 1 RESETN VCC3 Adjustable Reset Trip Threshold 2.31V 4 1.8V VCC18 2.26kΩ 1% System Reset AS1920-18 3 2 VCCA GND 22.6kΩ 1% Figure 17. Triple-Supply Monitor w/Manual Reset Switch VTRIP = VCCA/R2 (R1 + R2) 2.5V VTRIP = 2.3V 1.8V 3V 5 100nF R1 = R2 ((VTRIP/VCCA) - 1) † R3 10kΩ 5% R1 130kΩ 0.1% 4 100nF VCC18 3 VCCA Normally Open Manual Reset Switch 1 RESETN VCC3 System Reset AS1920-18 2 GND R2 100kΩ 0.1% † Optional Resistor Recommended to Extend ESD Tolerance www.austriamicrosystems.com Revision 1.00 10 - 14 AS1920/AS1922 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 The devices are available in an 5-pin SOT23 package. Figure 18. 5-pin SOT23 Package Symbol A A1 A2 b C D E E1 L e e1 α Min Max 0.90 1.45 0.00 0.15 0.90 1.30 0.30 0.50 0.09 0.20 2.80 3.05 2.60 3.00 1.50 1.75 0.30 0.55 0.95 REF 1.90 REF 0º 8º Notes: 1. 2. 3. 4. 5. 6. All dimensions in millimeters. Foot length measured at intercept point between datum A and lead surface. Package outline exclusive of mold flash and metal burr. Package outline inclusive of solder plating. Complies with EIAJ SC74. PKG ST 0003 Rev A supersedes SOT23-D-2005 Rev C. www.austriamicrosystems.com Revision 1.00 11 - 14 AS1920/AS1922 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 Tape and Reel Pin1 Orientation Figure 19. AS1920 Tape&Reel Pin1 Orientation User direction of feed Top, Through View SOT23-5 SOT23-5 SOT23-5 SOT23-5 Figure 20. AS1922 Tape&Reel Pin1 Orientation User direction of feed Top, Through View SOT23-5 www.austriamicrosystems.com SOT23-5 SOT23-5 Revision 1.00 SOT23-5 12 - 14 AS1920/AS1922 Datasheet - O r d e r i n g I n f o r m a t i o n 11 Ordering Information The devices are available as the standard products shown in Table 5. Table 5. Ordering Information Model Marking Description Reset Type Delivery Form Package AS1920-18-T ASI1 Triple-Voltage Supervisory Circuit: 3V, 1.8V, and Adjustable. Push/Pull Tape and Reel 5-pin SOT23 AS1922-18-T ASI2 Triple-Voltage Supervisory Circuit: 3V, 1.8V, and Adjustable. Open-Drain Tape and Reel 5-pin SOT23 www.austriamicrosystems.com Revision 1.00 13 - 14 AS1920/AS1922 Datasheet Copyrights Copyright © 1997-2007, austriamicrosystems AG, Schloss Premstaetten, 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 lifesustaining 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. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriamicrosystems AG rendering of technical or other services. Contact Information Headquarters austriamicrosystems AG A-8141 Schloss Premstaetten, Austria Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact www.austriamicrosystems.com Revision 1.00 14 - 14