SCANSTA476
Eight Input IEEE 1149.1 Analog Voltage Monitor
General Description
The SCANSTA476 is a low power, Analog Voltage Monitor
used for sampling or monitoring up to 8 analog/mixed-signal
input channels. Analog Voltage Monitors are valuable during
product development, environmental test, production, and
field service for verifying and monitoring power supply and
reference voltages. In a supervisory role, the 'STA476 is
useful for card or system-level health monitoring and prog-
nostics applications.
Instead of requiring an external microcontroller with a GPIO
interface, the 'STA476 features a common IEEE 1149.1
(JTAG) interface to select the analog input, initiate a mea-
surement, and access the results - further extending the
capabilities of an existing JTAG infrastructure.
The SCANSTA476 uses the V
REF
input as a reference. This
enables the SCANSTA476 to operate with a full-scale input
range of 0 to V
DD
, which can range from +2.7V to +5.5V.
The SCANSTA476 is packaged in a 16-lead non-pullback
LLP package that provides an extremely small footprint for
applications where space is a critical consideration. This
product operates over the industrial temperature range of
-40C to +85C.
Features
n
Eight selectable Analog input channels
n
Analog full-scale input range 0V to V
DD
n
Typical accuracy of 2 mV at maximum V
DD
n
Very low power operation
n
Small package footprint in 16-lead, 5 x 5 x 0.8 mm LLP
n
Single +2.7V to +5.5V supply operation
n
IEEE 1149.1 (JTAG) compliant interface
Applications
n
Measurement of Point Voltages
n
Real-time Signal Monitoring
n
System Health Monitoring and Prognostics
n
Debug, Environmental Test, Production Test, Field
Service
n
Supplement In-Circuit Tester (ICT) access
n
Vital in Servers, Computing, Telecommunication and
Industrial equipment
n
Essential in Medical, Data Storage, and Networking
equipment
Block Diagram
20083521
April 2005
SCANST
A476
Eight
Input
IEEE
1
149.1
Analog
V
oltage
Monitor
2005 National Semiconductor Corporation
DS200835
www.national.com
Connection Diagram
20083522
DAP = GND
(Top View)
Pin Descriptions
Pin No.
Symbol
Description
ANALOG I/O
16
A0
Analog input 0. This signal can range from 0V to V
REF
.
15
A1
Analog input 1. This signal can range from 0V to V
REF
.
14
A2
Analog input 2. This signal can range from 0V to V
REF
.
13
A3
Analog input 3. This signal can range from 0V to V
REF
.
12
A4
Analog input 4. This signal can range from 0V to V
REF
.
11
A5
Analog input 5. This signal can range from 0V to V
REF
.
10
A6
Analog input 6. This signal can range from 0V to V
REF
.
9
A7
Analog input 7. This signal can range from 0V to V
REF
.
2
V
REF
Analog reference voltage input. V
REF
must be
V
DD
. This pin should be connected to a quiet
+2.7V to +5.5V source (not directly to V
DD
) and bypassed to GND with 0.1 F and 1 F
monolithic capacitors located within 1 cm of the V
REF
pin.
DIGITAL I/O
6
TDI
Test Data Input to support IEEE 1149.1 features
5
TDO
Test Data Ouput to support IEEE 1149.1 features
7
TMS
Test Mode Select to support IEEE 1149.1 features
8
TCK
Test Clock to support IEEE 1149.1 features
4
TRST
Test Reset to support IEEE 1149.1 features
POWER SUPPLY
1,3
V
DD
Positive supply pin. These pins should be connected to a quiet +2.7V to +5.5V source and
bypassed to GND with 0.1 F and 1 F monolithic capacitors located within 1 cm of the
power pin.
(Note 1)
GND
Ground reference for CMOS circuitry. DAP is the exposed metal contact at the bottom of the
LLP package. The DAP is used as the primary GND connection to the device. It should be
connected to the ground plane with at least 4 vias for optimal low-noise and thermal
performance.
Note 1: Note that GND is not an actual pin on the package, the GND is connected thru the DAP on the back side of the LLP package.
SCANST
A476
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2
Absolute Maximum Ratings
(Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage V
DD
-0.3V to +6.5V
Voltage on Any Analog Pin to GND
-0.3V to V
DD
+0.3V
Voltage on Any Digital Pin to GND
-0.3V to V
DD
+0.3V
Input Current at Any Pin (Note 4)
10 mA
ESD Susceptibility
Human Body Model
Machine Model
8000V
>
250V
Soldering Temperature
Refer to AN-1187
Junction Temperature
+150C
Storage Temperature
-65C to +150C
Thermal Resistance,
JA
42C/W
Thermal Resistance,
JC
14.3C/W
Recommended Operating
Conditions
Operating Temperature Range
-40C
T
A
+85C
V
DD
Supply Voltage
+2.7V to +5.5V
Digital Input Pins Voltage Range
+0V to V
DD
Analog Input Pins Voltage Range
(Note 5)
+0V to V
REF
SCANSTA476 Electrical Characteristics
The following specifications apply for V
DD
= +2.7V to 5.5V, f
TCK
= 20 MHz, unless otherwise noted.
Symbol
Parameter
Conditions
Typical
Limits
Units
POWER SUPPLY CHARACTERISTICS
V
DD
Supply Voltage
-40C
T
A
85C
2.7
V (min)
5.5
V (max)
I
DD
Normal Mode (Static)
V
DD
= +2.7V to +5.5V,
3.5
5.0
mA
Normal Mode (Operational)
V
DD
= +2.7V to +5.5V,
f
TCK
= 1 MSPS
5.0
mA (max)
P
D
Power Consumption, Normal Mode
(Operational)
V
DD
= +5.5V, f
TCK
= 1 MSPS
27.5
mW (max)
ANALOG INPUT CHARACTERISTICS (A0-A7)
V
IN
Analog Input Range
V
REF
V
DD
0 to V
REF
V
V
REF
Reference Voltage Range
V
DD
-
0.5V to
V
DD
V
I
DCL
DC Leakage Current
0.1
10
A (max)
V
MEAS
Analog Input Measurement Accuracy
V
DD
= +2.7V
1
7.5
mV
V
DD
= +5.5V
2
15
DIGITAL INPUT CHARACTERISTICS (TDI, TMS, TCK, TRST)
V
IH
Input High Voltage
V
DD
= +2.7V to +3.6V
2.0
V (min)
V
DD
= +5.5V
2.1
V
IL
Input Low Voltage
V
DD
= +5V
0.8
V (max)
V
CL
Input Clamp Voltage
I
CL
= -18mA
-0.8
-1.5
V (max)
I
IN
Input Current
V
IN
= 0V or V
DD
0.2
10
A (max)
I
ILR
Input Current
TRST, TDI, TMS only
-300
A (max)
DIGITAL OUTPUT CHARACTERISTICS (TDO)
V
OH
Output High Voltage
I
OH
= -100 A, 2.7V
V
DD
5.5V
V
DD
-0.2
V (min)
I
OH
= -4 mA, 3.0V
V
DD
5.5V
2.4
V (min)
I
OH
= -4 mA, V
DD
= 2.7V
2.2
V (min)
V
OL
Output Low Voltage
I
OL
= 100 A, 2.7V
V
DD
5.5V
0.2
V (max)
I
OL
= 4 mA, 2.7V
V
DD
5.5V
0.4
V (max)
I
OS
Output Short Circuit Current
V
OUT
= 0V, V
DD
= 5.5V
-85
mA (max)
I
OZ
TRI-STATE Leakage Current
10
A (max)
Output Coding
Straight (Natural) Binary
SCANST
A476
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SCANSTA476 Electrical Characteristics
(Continued)
The following specifications apply for V
DD
= +2.7V to 5.5V, f
TCK
= 20 MHz, unless otherwise noted.
Symbol
Parameter
Conditions
Typical
Limits
Units
AC ELECTRICAL CHARACTERISTICS
F
MAX
Throughput Rate
TCK = 20MHz
1
MSPS
(max)
INPUT TIMING CHARACTERISTICS
t
SET
TDI to TCK (H/L)
(Note 3)
2.0
ns (min)
t
HOLD
TDI to TCK (H/L)
(Note 3)
1.5
ns (min)
t
SET
TMS to TCK (H/L)
(Note 3)
2.0
ns (min)
t
HOLD
TMS to TCK (H/L)
(Note 3)
2.0
ns (min)
t
W
TCK Pulse Width (H/L)
(Note 3)
10.0
ns (min)
t
REC
Recovery TIme TRST to TCK
(Note 3)
2.0
ns (min)
t
W
TRST Pulse Width (L)
(Note 3)
2.5
ns (min)
F
MAX
TCK
20
MHz (min)
Note 2: Absolute maximum ratings are limiting values, to be applied individually, and beyond which the serviceability of the circuit may be impaired. Functional
operability under any of these conditions is not implied. Exposure to maximum ratings for extended periods may affect device reliability.
Note 3: Data sheet min/max specification limits are guaranteed by design or statistical analysis.
Note 4: Except power supply pins.
Note 5: For valid measurements, the analog V
IN
<
V
REF
V
DD
.
Applications Information
POWER-UP TIMING
The SCANSTA476 typically requires 1 s to power up ,
either after first applying V
DD
, or after an incomplete conver-
sion shift. To return to normal, one "dummy" conversion must
be fully completed. After this first dummy conversion, the
SCANSTA476 will perform conversions properly.
STARTUP MODE
When the V
DD
supply is first applied, the SCANSTA476
requires one dummy conversion after start-up.
SCANST
A476
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Timing
Diagrams
Instruction
Shift
(Channel
Select)
20083532
Op-codes
40h
to
47h
select
pins
A0
to
A7
respectively.
Note
the
JTAG
reset
preamble
places
the
JTAG
TAP
controller
in
a
stable
state
(RTI).
Both
the
instruction
and
data
shifts
start
in
-
and
return
to
-
the
RTI
state.
SCANST
A476
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