D a ta s h e e t
AS1927
N a n o p o w e r µ P S u p e r v i s o r y C i r c u i ts w i t h M a n u a l
R e s e t a n d Wa t c h d o g Tim e r
1 General Description
The AS1927 microprocessor supervisory circuits were
designed to generate a reset when the monitored supply
voltage falls below a factory-trimmed threshold. The
reset remains asserted for a minimum timeout period
after the supply voltage stabilizes.
Guaranteed to be in the correct state for V
CC
higher than
+1.0V, these devices are ideal for portable and battery-
powered systems with strict monitoring requirements.
The devices feature factory-trimmed thresholds to moni-
tor a supply voltage between 1.575V and 4.625V.
The devices are available with the reset output types
listed in
Table 1.
Table 1. Standard Products
Model
AS1927L
AS1927H
AS1927D
Reset Output Type
Active-Low Push/Pull
Active-High Push/Pull
Active-Low Open-Drain
2 Key Features
!
!
170nA Ultra-Low Supply Current
V
CC
Supervisory Range: +1.575V to +4.625V
(for further information see
Ordering Information on
page 10)
Guaranteed Reset Valid Down to V
CC
= +1.0V
Six Minimum Reset Timeout Period Options from:
10ms to 1.2s
Manual Reset Input
Watchdog Timeout Period: 1.5s or 1.5min
Three Reset Output Types
- Active-Low Push/Pull (AS1927L)
- Active-High Push/Pull (AS1927H)
- Active-Low Open-Drain (AS1927D)
!
!
!
!
!
!
!
Immune to Fast Negative V
CC
Transients
External Components Not Required
Operating Temperature Range: -40 to +85°C
6-pin TDFN (2x2mm) Package
The AS1927 include a manual-reset input for systems
that never fully power down the microprocessor.
Additionally, these devices feature a watchdog timer to
ensure that the processor is operating within proper
code boundaries. A watchdog disable feature allows to
turn off the watchdog if not required or unwanted, as in
boot up conditions of microcontrollers.
The AS1927 are available in a 6-pin TDFN (2x2mm)
package.
!
!
3 Applications
The devices are ideal for low-power portable and bat-
tery-powered systems, embedded controllers, intelligent
instruments, automotive systems, and critical CPU mon-
itoring applications.
Figure 1. AS1927 - Typical Application Diagram
I/O Supply
V
CC
6
1
RESETN
RESETN
VCC
3
External
Reset
MRN
5
WDD
AS1927L/
AS1927D
4
WDI
2
GND
I/O
CPU
GND
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AS1927
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
RESETN/RESET 1
6 VCC
GND 2
AS1927
5 WDD
MRN 3
4 WDI
Pin Descriptions
Table 2. Pin Descriptions
Pin Number
Pin Name
Description
Active-Low Reset Output
(AS1927L, AS1927D). The RESETN signal toggles from
high to low when V
CC
crosses the threshold (falling), or MRN is pulled low, or the
watchdog triggers a reset. This output signal remains low for the reset timeout period
(see t
RP
on
page 4)
after the supervised voltage exceeds its reset threshold, or MRN
goes low to high.
Active-High Reset Output
(AS1927H). The RESET signal toggles from low to high
when V
CC
crosses the threshold (falling), or MRN is pulled low, or the watchdog triggers
a reset. This output signal remains high for the reset timeout period (see t
RP
on
page 4)
after the supervised voltage exceeds its reset threshold, or MRN goes low to high.
Ground
Active-Low Manual Reset Input.
Pulling this pin low asserts a reset. This pin is
connected to the internal 20kΩ pullup to V
CC
. This reset remains active as long as MRN
is low and for the reset timeout period (see t
RP
on
page 4)
after MRN goes high.
Note:
If the manual reset feature is not used, this pin should be unconnected or con-
nected to V
CC
.
Watchdog Input.
If WDI remains high or low for longer than the watchdog timeout
period (see t
WD
on
page 5),
the internal watchdog timer period expires and a reset is
triggered for the reset timeout period (see t
RP
on
page 4).
The internal watchdog timer
clears whenever a reset is asserted or when WDI senses a rising or falling edge.
Watchdog Disable.
This pin allows to turn on or off the watchdog feature.
Pin to GND: Watchdog enabled.
Pin to V
CC
: Watchdog disabled.
Supervised Voltage Input.
This pin serves as the supervised supply voltage input.
RESETN
1
RESET
2
GND
3
MRN
4
WDI
5
6
WDD
VCC
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AS1927
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 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
Open-Drain RESETN
Push/Pull RESET, RESETN
MRN, WDI to GND
Input and Output Current (all pins)
ESD
Continuous Power Dissipation
(T
AMB
= +70ºC)
Operating Temperature Range
Junction Temperature
Storage Temperature Range
-65
-40
1
696
+85
+150
+150
Min
-0.3
-0.3
-0.3
-0.3
Max
+7.0
+7.0
V
CC
+
0.3
V
CC
+
0.3
20
Units
V
V
V
V
mA
kV
mW
ºC
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC J-STD-020D “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).
HBM MIL-Std. 883E 3015.7
methods
Derate 8.7mW/ºC above +70ºC
Comments
Package Body Temperature
+260
ºC
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AS1927
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
V
CC
= +1.2V to +5.5V; T
AMB
= -40°C to +85ºC. Typ values are @ T
AMB
= +25°C (unless otherwise specified).
Table 4. Electrical Characteristics
Symbol
V
CC
Parameter
1
Conditions
T
AMB
= 0 to +85ºC
T
AMB
= -40 to +85ºC
No Load, V
CC
= +5.0V
No Load, V
CC
= +3.3V
No Load, V
CC
= +1.8V
V
CC
falling
Min
1.0
1.2
Typ
Max
5.5
5.5
Units
V
Operating Voltage Range
210
190
170
-2
400
380
370
2
170
%
ppm/
ºC
%/
V
TH
µs
25
80
300
600
1200
2400
0.3
0.3
V
0.3
0.3
ms
nA
I
CC
V
TH
V
CC
Supply Current
V
CC
Reset Threshold
Reset Threshold
2
Temperature Coefficient
Reset Threshold Hysteresis
0.5
V
CC
= (V
TH
+ 100mV) to (V
TH
- 100mV)
@ 10mV/µs
D1
D2
V
CC
= (V
TH
-2%) to (V
TH
+
150mV)
D3
D4
D5
D6
V
CC
≥
1.0V, I
SINK
= 50µA,
Reset Asserted, T
AMB
= 0 to +85ºC
10
40
150
300
600
1200
40
15
60
225
450
900
1800
t
RD
V
CC
to Reset
Output Delay
t
RP
Reset Timeout Period
V
OL
RESETN Output Low
(Push/Pull or Open-Drain)
V
CC
≥
1.2V, I
SINK
= 100µA,
Reset Asserted
V
CC
≥
2.12V, I
SINK
= 1.2mA,
Reset Asserted
V
CC
≥
3.3V, I
SINK
= 3.2mA,
Reset Asserted
V
CC
≥
1.71V, I
SOURCE
= 200µA,
Reset Not Asserted
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
V
OH
RESETN Output High
(Push/Pull Only)
V
CC
≥
2.38V, I
SOURCE
= 500µA,
Reset Not Asserted
V
CC
≥
3.3V, I
SOURCE
= 800µA,
Reset Not Asserted
V
I
LKG
Open-Drain RESETN Output
Leakage Current
RESETN Not Asserted
V
CC
≥
1.0V, I
SOURCE
= 10µA,
Reset Asserted, T
AMB
= 0 to +85ºC
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
0.8 x
V
CC
25
nA
V
OH
RESET Output High
(Push/Pull Only)
V
CC
≥
1.50V, I
SOURCE
= 200µA,
Reset Asserted
V
CC
≥
2.12V, I
SOURCE
= 500µA,
Reset Asserted
V
CC
≥
3.3V, I
SOURCE
= 800µA,
Reset Asserted
V
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AS1927
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
Table 4. Electrical Characteristics (Continued)
Symbol
Parameter
1
Conditions
V
CC
≥
1.71V, I
SINK
= 500µA,
Reset Asserted
Min
Typ
Max
0.3
0.3
0.3
Units
V
OL
RESET Output Low
(Push/Pull Only)
V
CC
≥
2.38V, I
SINK
= 1.2mA,
Reset Asserted
V
CC
≥
3.3V, I
SINK
= 3.2mA,
Reset Asserted
V
Manual Reset Input
V
IH
MRN Input voltage
V
IL
MRN Minimum Input Pulse
MRN Transient Rejection
MRN to Reset Delay
MRN Pullup Resistance
Watchdog Input
V
IH
WDI Input Voltage
V
IL
V
IHE
WDD Input Voltage
V
ILE
S
t
WD
Watchdog Timeout Period
M
L
X
t
WDI
I
WDI
WDI Pulse Width
2
2
2
0.7 x
V
CC
0.3 x
V
CC
1
200
250
20
0.7 x
V
CC
0.3 x
V
CC
0.7 x
V
CC
0.3 x
V
CC
3.3
6
12
24
150
WDI = V
CC
, Time Average
20
V
µs
ns
ns
kΩ
V
V
s
ns
nA
WDI Input Current
1. Over-temperature limits are guaranteed by design and not production tested. Devices tested at +25ºC.
2. Guaranteed by design and not production tested.
Note:
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or
SQC (Statistical Quality Control) methods.
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