AS1920

AS1920, AS1922 T r 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 D a ta S h e e t 1 General Description 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 AS1920-18 AS1922-18 Output Type Push/Pull Open-Drain Supervisory Voltages 3V, 1.8V, Adjustable 3V, 1.8V, Adjustable 2 Key Features ! 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 ! ! ! ! ! ! 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. The AS1920 and AS1922 are available in a 5-pin SOT23 package. ! ! 3 Applications 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 1.8V 2.5V 5 VCC3 4 R1 130kΩ 1% 0.1µF R2 100kΩ 1% VCC18 3 VCCA System Logic AS1920/ AS1922 1 RESETN 2 GND 0.1µF www.austriamicrosystems.com Revision 1.00 1 - 14 AS1920/AS1922 Datasheet - P i n o u t 4 Pinout Pin Assignments Figure 2. Pin Assignments (Top View) RESETN 1 5 VCC3 GND 2 AS1920/ AS1922 VCCA 3 4 VCC18 Pin Descriptions Table 2. Pin Descriptions Pin Number Pin Name Description 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. Ground. VCCA. 1V sense, high-impedance input. Note: If this pin is not used it should be tied to VCC3 or 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. 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. 1 RESETN 2 3 GND VCCA 4 VCC18 5 VCC3 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 VCC18, VCC3, VCCA to GND RESETN Open-Drain RESETN to GND Min -0.3V -0.3 -0.3 Max +5 +7 VCC3 + 0.3 Units V V V 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). Comments Operating Temperature Range -40 +85 ºC Storage Temperature Range -65 +150 ºC Package Body Temperature +260 ºC www.austriamicrosystems.com Revision 1.00 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 VRT18 VRT3 VRTA VCC3, VCC18 IVCC18 IVCC3 IVCCA IOUT ILEAK tRST tUV 1 Parameter Reset Threshold VCC18 Reset Threshold VCC3 Reset Threshold VCCA Operating Voltage VCC18 Supply Current VCC3 Supply Current VCCA Input Current Open-Drain RESETN Output Current Open-Drain RESETN Output Leakage Current Reset Pulse Width VCC Undervoltage Detect to RESETN Conditions Min 1.653 2.763 0.982 Typ 1.683 2.805 1.00 Max 1.713 2.847 1.018 3.3 Unit V V V V µA µA nA µA µA ms µs RESETN in Correct Logic State VCC18 < VCC3, VCC18 = 1.8V VCC18 < VCC3, VCC3 = 3V VCCA = 1V Reset Not Asserted, Forced to 0V Reset Not Asserted, RESETN Forced to 5.5V, TAMB = 25ºC RESETN Low, TAMB = 25ºC VCC18, VCC3, or VCCA < 2 Reset Threshold by > 1% TAMB = 25ºC ISINK = 2.5mA, VCC3 = 3V, VCC18 = 0V ISINK = 100µA, VCC3 = 1V, VCC18 = 0V ISINK = 100µA, VCC3 = 0V, VCC18 = 1V ISINK = 100µA, VCC3 = 1V, VCC18 = 1V 2 1 0.7 6.2 -15 2 -0.1 140 200 130 0 4 2 15 15 13 0.1 280 0.15 0.05 0.05 0.05 VCC3 1 VCC3 0.65 0.4 0.3 V 0.3 0.3 V VOL Output Voltage Low, RESETN VOH Output Voltage High, RESETN ISOURCE = 1µA (AS1922-xx) 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 1 Figure 4. IVCC3 vs. Temperature; VCC3 = 3V 6.5 6.4 VCC18 Supply Current (µA) e 0.9 VCC3 Supply Current (µA) e 6.3 6.2 6.1 6 5.9 5.8 5.7 5.6 5.5 -100 -50 0 50 100 0.8 0.7 0.6 0.5 -100 -50 0 50 100 Temperature (°C) Figure 5. Supply Current VCCA vs. Temperature 10 Temperature (°C) Figure 6. VOH/RST vs. Temperature; VCC3 = 3V 2.5 2.45 VCCA Supply Current (nA) e 9 7 6 5 4 3 2 1 0 -100 -50 0 50 100 Output Voltage High e 8 2.4 2.35 2.3 2.25 2.2 -100 -50 0 50 100 Temperature (°C) Figure 7. tRST vs. Temperature; VCC3 = VCCA = 3V 280 Temperature (°C) Figure 8. tUV vs. Temperature; VCC3 = VCCA = 3V 150 Reset Pulse Width (ms) e 260 240 220 200 180 160 140 -100 VCC Undervoltage Detect [µs] e 125 100 75 -50 0 50 100 50 -100 -50 0 50 100 Temperature (°C) Temperature (°C) www.austriamicrosystems.com 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 4 VCC Internal + VCC3 VCC18 200ms Pulse Generator – 200ms Delay 1 RESETN + 3 – VCCA + 2 GND Bandgap Reference AS1920 Figure 10. VCC Monitor Timing Diagram VCCX VRTX tRST tUV RESETN 1.5V www.austriamicrosystems.com 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 4 VCC Internal + VCC3 IOUT 200ms Pulse Generator 1 RESETN 200ms Delay VCC18 – + 3 – VCCA + 2 GND Bandgap Reference AS1922 www.austriamicrosystems.com Revision 1.00 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 3V 5 VCC3 4 VCC18 3 1.8V AS1920/ AS1922 1 RESETN 2 GND R3 100kΩ Adjustable Supply R1 VCCA 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 VCC3 4 VCC18 Adjustable Supply or DC/DC Feedback Divider 3 R1 R2 VCCA 1 RESETN System Reset 1.8V AS1920-18 2 GND 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 VCC3 4 VCC18 3 VCCA 1 RESETN System Reset 1.8V AS1920-18 2 GND Figure 15. Dual-Supply Monitor (3V and Adjustable) 3V 5 VCC3 4 VCC18 1 RESETN System Reset AS1920-18 2 GND Adjustable Supply or DC/DC Feedback Divider To ensure threshold accuracy, set the parallel combination of R1 and R2 ≤ 66.5kΩ 3 R1 R2 VCCA www.austriamicrosystems.com 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% Adjustable Reset Trip Threshold 2.31V 2.26kΩ 1% 3V 5 VCC3 4 VCC18 3 VCCA 1 RESETN System Reset 1.8V AS1920-18 2 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 1 RESETN System Reset R1 = R2 ((VTRIP/VCCA) - 1) R1 130kΩ 0.1% 100nF VCC3 4 R3 10kΩ 5% † 100nF VCC18 3 VCCA AS1920-18 2 GND Normally Open Manual Reset Switch 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 Top, Through View User direction of feed SOT23-5 SOT23-5 SOT23-5 SOT23-5 Figure 20. AS1922 Tape&Reel Pin1 Orientation Top, Through View User direction of feed SOT23-5 SOT23-5 SOT23-5 SOT23-5 www.austriamicrosystems.com Revision 1.00 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 AS1920-18-T AS1922-18-T Marking ASI1 ASI2 Description Triple-Voltage Supervisory Circuit: 3V, 1.8V, and Adjustable. Triple-Voltage Supervisory Circuit: 3V, 1.8V, and Adjustable. Reset Type Push/Pull Open-Drain Delivery Form Tape and Reel Tape and Reel Package 5-pin SOT23 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. 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