AS1925-BSTT-D07 [AMSCO]
Ultra-Low Voltage Microprocessor Supervisory Circuit with Manual Reset; 超低电压微处理器监控电路，带有手动复位
| 型号： | AS1925-BSTT-D07 |
| 厂家： | 
AMS(艾迈斯) |
| 描述： | Ultra-Low Voltage Microprocessor Supervisory Circuit with Manual Reset |
| 文件： | 总12页 (文件大小：340K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Data Sheet
AS1925, AS1926
Ultra-Low Voltage Microprocessor Supervisory
Circuit with Manual Reset
1 General Description
2 Key Features
ꢀ
Factory-Trimmed Reset Thresholds for Monitoring
Supplies from 0.9 to 1.5V
The AS1925/AS1926 microprocessor supervisory cir-
cuits were designed to assert a single reset if the moni-
tored supply voltage drops below its reset threshold or if
the manual reset is activated. The reset remains
asserted for a fixed timeout delay after VCC has risen
above the reset threshold and the manual reset is deas-
serted.
ꢀ
ꢀ
Low Power Consumption: 3.5µA
Reset Threshold Accuracy Over Temperature:
±2.5%
Their small size, excellent circuit reliability, and low sup-
ply current (3.5µA) make the AS1925/AS1926 a very
low cost solution by eliminating external components
and adjustments when used with low-voltage (+0.9 to
+1.5V) systems.
ꢀ
ꢀ
Four Timeout Periods: 1.5ms, 30ms, 210ms, and
1.68s
Three Reset Output Types:
- Active-Low Push/Pull
- Active-High Push/Pull
- Active Low Open-Drain
The devices are available as the standard products
listed in Table 1.
Table 1. Standard Products
Model
Output Type
ꢀ
Guaranteed Reset Valid to VCC = 0.55V (Active-
Low)
Active-Low Push/Pull,
Active-High Push/Pull
AS1925
ꢀ
ꢀ
ꢀ
Manual Reset Input
Active-High Push/Pull,
Active-Low Open-Drain
AS1926
Immune to Fast VCC Transients
5-pin SOT23 Package
The active-low open-drain reset output requires a pullup
resistor that can be connected to a voltage from 0 to
VCC. The reset comparator was specifically designed to
ignore fast VCC transients.
The devices are available in a 5-pin SOT23 package.
3 Applications
The device is ideal for portable and battery-powered
systems, embedded controllers, intelligent instruments,
automotive systems, telecommunications equipment,
networking equipment, computer workstations and serv-
ers, critical CPU monitoring applications, and any low-
voltage application.
Figure 1. Block Diagram and Pinout
4
MRN
AS1925/
RESETN
GND
1
2
3
5
VCC
AS1926
5
VCC
MRN
Pullup
Manual Reset
Detect
+
–
VREF
3
AS1925/
AS1926
RESET
1
Reset
Output
+
–
ResetTimeout
Period
RESETN
RESET
4
MRN
GND
2
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AS1925/AS1926
Data Sheet - Pinout
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
RESETN
GND
1
2
3
5
VCC
AS1925/
AS1926
RESET
4
MRN
Pin Descriptions
Table 2. Pin Descriptions
Pin
Pin Number
Description
Name
Active-Low Reset Output – AS1925 Push/Pull or AS1926 Open-Drain.
RESETN changes from high to low if VCC drops below the selected reset
threshold or MRN is pulled low. RESETN remains low for the reset timeout
period (see page 4) after VCC exceeds the device reset threshold and MRN is
released high.
1
RESETN
Ground
2
GND
Active-High Push/Pull Reset Output. RESET changes from low to high when
VCC input drops below the selected reset threshold or MRN is pulled low. RESET
remains high for the reset timeout period (see page 4) after VCC exceeds the
device reset threshold and MRN is released high.
3
RESET
Active-Low Manual Reset Input. This pin is connected to the internal 20kΩ
pullup to VCC. Pull this pin low to force a reset. The reset remains active as long
as MRN is low and for the reset timeout period (see page 4) after MRN goes
high.
4
5
MRN
VCC
Note: If this pin is not used it should be connected to VCC or left unconnected.
Supply Voltage. Monitored supply voltage.
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AS1925/AS1926
Data Sheet - Absolute Maximum Ratings
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 Character-
istics 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
VCC to GND
Min Max Units
Comments
-0.3
-0.3
+5
+5
V
V
MRN, RESETN (Open-Drain) to GND
VCC+
0.3
RESETN (Push/Pull), RESET to GND
-0.3
V
Input Current (All Pins)
RESETN, RESET Output Current
Continuous Power Dissipation (TAMB = +70ºC)
Operating Temperature Range
Junction Temperature
20
20
mA
mA
571 mW
Derate 7.1mW/ºC above +70ºC
-40
+85
ºC
ºC
ºC
+150
Storage Temperature Range
-65 +150
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).
Package Body Temperature
+260
ºC
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AS1925/AS1926
Data Sheet - Electrical Characteristics
6 Electrical Characteristics
VCC = +0.55 to +1.8V, TAMB = -40 to +85ºC (unless otherwise specified). Typ values @ TAMB = +25ºC.
Table 4. Electrical Characteristics
Parameter 1
Symbol
Conditions
Min
Typ
Max
Units
Supply Voltage Range 2
VCC
0.75
1.80
V
VCC = 0.9V, No Load, Reset Not Asserted
3.5
4.5
12
ICC
Supply Current
VCC = 1.5V, No Load, Reset Not Asserted
12
µA
VCC = 1.8V, No Load, Reset Not Asserted
5
12
Suffix 14
Suffix 13
1.350
1.275
1.080
1.020
0.810
0.765
1.388
1.313
1.110
1.050
0.833
0.788
1.425
1.350
1.140
1.080
0.855
0.810
Suffix 11
Reset Threshold
(VCC Falling)
VTH
V
Suffix 10
Suffix 08
Suffix 07, TAMB = 0 to +85ºC
Reset Threshold
Hysteresis
VHYS
0.75
120
%VTH
µs
VCC Falling, Step Signal from (VTH + 10%)
to (VTH - 10%) within 1µs
VCC to Reset Delay
Suffix B
Suffix C
Suffix D
Suffix E
1
1.5
30
2
20
40
Reset Active Timeout
Period
tRP
ms
140
1120
210
1680
280
2240
0.3 ×
VCC
VIL
VIH
MRN Input Voltage 3
V
0.7 ×
VCC
MRN Minimum Input
Pulse Width
MRN driven from VCC to 0V 3
1
µs
MRN driven from VCC to 0V 3
MRN driven from VCC to 0V 3
MRN Glitch Rejection
MRN to Reset Delay
150
500
ns
ns
MRN Pullup Resistance
to VCC
10
20
26
kΩ
0.2 ×
VCC
VCC = 0.55V, ISINK = 10µA, Reset Asserted
VCC = 0.83V, ISINK = 80µA, Reset Asserted
VCC > VTH, Reset Not Asserted
RESETN Open-Drain
Output Voltage
VOL
ILEAK
VOL
V
0.2 ×
VCC
RESETN Open-Drain
Output Leakage Current
1
µA
0.2 ×
VCC
VCC = 0.55V, ISINK = 10µA, Reset Asserted
VCC = 0.83V, ISINK = 80µA, Reset Asserted
RESETN Push/Pull
Output Voltage
0.2 ×
VCC
V
VCC = 0.83V, ISOURCE = 40µA,
Reset Not Asserted
0.8 ×
VCC
VOH
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AS1925/AS1926
Data Sheet - Electrical Characteristics
Table 4. Electrical Characteristics (Continued)
Parameter 1
Symbol
Conditions
Min
Typ
Max
Units
VCC = 0.75V, ISOURCE = 10µA,
Reset Asserted
0.8 ×
VCC
VOH
VOL
RESET Push/Pull Output
Voltage
VCC = 0.83V, ISOURCE = 40µA,
Reset Asserted
0.8 ×
VCC
V
VCC = 0.83V, ISINK = 80µA,
Reset Not Asserted
0.2 ×
VCC
1. 100% production tested at +25ºC. Over-temperature limits are guaranteed by design.
2. The active-low output RESETN VCC(MIN) = 0.55V.
3. For VCC > 0.788V, TAMB = 0 to +85ºC; for VCC > 0.833V, TAMB = -40 to +85ºC.
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AS1925/AS1926
Data Sheet - Typical Operating Characteristics
7 Typical Operating Characteristics
VCC = 1.5V, TAMB = +25ºC (unless otherwise specified).
Figure 3. Supply Current vs. Temperature
Figure 4. Power Down Reset Delay vs. Temperature
140
120
100
80
5
V
=1.8V
CC
V
= 100mV
OD
4
3
2
1
0
V
= 1.5V
CC
V
= 0.9V
CC
V
= 20mV
= 10mV
OD
60
40
V
OD
20
V
= Overdrive Voltage
OD
0
-40
-15
10
35
60
85
-40
-15
10
35
60
85
Temperature (°C)
Temperature (°C)
Figure 5. Normalized Reset Timeout Periode vs. Temp.
Figure 6. Normalized VCC Reset TH. vs. Temperature
1.08
1.01
1.06
1.04
1.02
1
1.005
1
0.995
0.99
0.98
0.96
-40
-15
10
35
60
85
0
15
30
45
60
75
90
Temperature (°C)
Temperature (°C)
Figure 7. Power-Up/Down Characteristics
Figure 8. Glitch rejection vs. Supply Voltage
700
600
500
Reset occures
above this line
400
300
No reset occures
below this line
200
100
0
1
10
100
100ms/Div
Overdrive VTH-VCC (mV)
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AS1925/AS1926
Data Sheet - Detailed Description
8 Detailed Description
Reset Output
The AS1925/AS1926 assert a reset during power-up, power-down, and brownout conditions if the VCC supply voltage
falls below a preset threshold (AS1925/AS1926). The reset remains asserted for a fixed timeout delay (see page 4)
once VCC has stabilized.
The devices are available with four timeout options: 1.5ms, 30ms, 210ms, and 1.68s.
The AS1925/AS1926 have two reset outputs (RESETN and RESET); RESETN is the inverse of RESET. The AS1925
has an active-high push/pull output and an active-low push/pull output. The AS1926 has an active-high push/pull out-
put and an active-low open-drain output.
Manual Reset Input
The devices feature a manual reset input (MRN). When pin MRN is pulled low, a reset is asserted and the reset
remains asserted as long as MRN is kept low, and for a fixed timeout delay after MRN goes high. MRN is connected to
an internal 20kΩ pullup resistor, thus this pin can be left open if it is not used.
MRN can be driven with CMOS logic-level or with open-drain/collector outputs.
To create a manual reset circuit, connect a normally open momentary switch from MRN to ground (see Figure 9 on
page 8). External debounce circuitry is not required. If pin MRN is driven via long cables or the device is used in a
noisy environment, a 0.1µF capacitor from MRN to ground will provide additional noise immunity.
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AS1925/AS1926
Data Sheet - Application Information
9 Application Information
Figure 9. Typical Application Diagram
+3.3V
0.9V
DC/DC
Converter
5
VCC
I/O
Supply
VCC
CPU
AS1926
1
RESETN
RESETN
4
External
Reset
GND
MRN
GND
2
Fast Transient Immunity
The AS1925/AS1926 are virtually immune to fast, falling VCC transients. Figure 8 on page 6 shows typical transient
duration versus reset comparator overdrive, for which the devices do not generate a reset pulse. The graph was gen-
erated using a falling pulse applied to VCC, starting 0.1V above the actual reset threshold and ending below it by the
magnitude indicated (reset comparator overdrive). The graph indicates the maximum pulse width that a falling VCC
transient can have without causing a reset pulse. As the magnitude of the transient goes further below the reset
threshold, the maximum allowable pulse width decreases.
Note: For additional transient immunity, place a 0.1µF bypass capacitor as close as is practical to pin VCC.
Ensuring a Valid Reset Output Down to 0V
If VCC falls below 0.55V, the AS1925 push/pull RESETN output will no longer sink current and becomes an open cir-
cuit, which means that high-impedance CMOS-logic inputs connected to RESETN can drift to undetermined voltages.
This is not relevant for most applications since most microprocessors and other circuits do not operate with a supply
voltage < 0.55V.
In systems where RESETN must be valid down to 0V, adding a pulldown resistor to RESETN (see Figure 10) causes
any stray leakage currents to flow to ground, holding RESETN low. The value of the pulldown resistor is not critical; a
200kΩ resistor is large enough not to load RESETN and small enough to pull RESETN to ground.
Figure 10. Reset Valid to VCC = 0V
5
VCC
1
AS1925
RESETN
RPULLDOWN
GND
2
Note: A 200kΩ pullup resistor to VCC is also recommended if the push/pull RESET is required to remain valid for VCC
0.75V.
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AS1925/AS1926
Data Sheet - Application Information
Interfacing to Bi-Directional Microprocessor Reset Pins
Because the RESETN output of the AS1926 is open drain, this device interfaces easily with microprocessors that have
bidirectional reset pins. Connecting the AS1926 RESETN output directly to the microprocessor RESETN pin with a
single pullup resistor allows either device to assert reset (Figure 11 on page 9).
Figure 11. Interfacing to Microprocessors with Bidirectional Reset Pins
VCC
VCC
5
VCC
1
CPU
AS1926
RESETN
RESETN
GND
GND
2
Using the AS1926 Open-Drain RESETN Output with Multiple Supplies
In a typical application, the pullup resistor connected to the AS1926 connects to the voltage being monitored at pin
VCC. However, some systems use an open-drain output to level-shift from the monitored supply to reset circuitry pow-
ered by another supply (see Figure 12).
As VCC decreases, so does the ability of the AS1926 to sink current at RESETN. RESETN is pulled high as VCC
decreases toward 0V. The voltage where this occurs depends on the value of the pullup resistor and the supply voltage
to which it is connected.
Figure 12. AS1926 Open-Drain RESETN Output with Multiple Supplies
+5.0V
VCC
5
RPULLUP
RESETN
+0.9V
VCC
1
CPU
AS1926
RESETN
GND
GND
2
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AS1925/AS1926
Data Sheet - Package Drawings and Markings
10 Package Drawings and Markings
The AS1925/AS1926 are available in an 5-pin SOT23 package.
Figure 13. 5-pin SOT23 Package
Notes:
Symbol
Min
0.90
0.00
0.90
0.30
0.09
2.80
2.60
1.50
0.30
Max
1.45
0.15
1.30
0.50
0.20
3.05
3.00
1.75
0.55
1. All dimensions are in millimeters.
A
A1
A2
b
2. Foot length is measured at the intercept point between datum
A and lead surface.
3. Package outline exclusive of mold flash and metal burr.
4. Package outline inclusive of solder plating.
5. Complies with EIAJ SC74.
C
D
6. Package ST003 Revision A supercedes SOT34-D-2005
Revision C.
E
E1
L
e
0.95 Ref
1.90 Ref
e1
α
0º
8º
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AS1925/AS1926
Data Sheet - Ordering Information
11 Ordering Information
The AS1925/AS1926 are available as the standard products shown in Table 5.
Table 5. Ordering Information
Model
Description
Timeout Period
Delivery Form
Package
Ultra-Low Reset Threshold with
Manual Reset
AS1925-BSTT-xyy1
AS1925-BSTT-D07
5-pin SOT23
Tape and Reel
Ultra-Low Reset Threshold (0.81V)
with Manual Reset
5-pin SOT23
5-pin SOT23
140ms Reset
140ms Reset
Tape and Reel
Tape and Reel
Ultra-Low Reset Threshold (0.81V)
with Manual Reset, Open-Drain
AS1926-BSTT-D07
1. xx and y is a placeholder for variants, e.g., AS1926-BSTT-D07 offers 0.81V (max) reset threshold and a 140ms
minimum timeout periode (see Table 6).
Available upon request. Contact austriamicrosystems, AG for more information.
Table 6. Model Variants
Suffix (x)
Reset timout (ms)
Suffix (yy)
Reset Threshold (V)
min typ max
min
1
typ
1.5
30
max
2
B
C
D
E
14
13
11
10
08
07
1.350 1.388 1.425
1.275 1.313 1.350
1.080 1.110 1.140
1.020 1.050 1.080
0.810 0.833 0.855
0.765 0.788 0.810
20
40
140
210
280
1120 1680 2240
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AS1925/AS1926
Data Sheet
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, trans-
lated, 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. austriami-
crosystems 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.
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 tech-
nical 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
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