AMI AMIS-70020 Power failure elapsed time counter Datasheet

AMIS-70020 Power Failure Elapsed Time Counter
Data Sheet
1.0 General Description
The few external components required to build the AMIS70020 into its application result in a cost effective solution
and in a footprint of less than 2cm2. The combination of an
internal oscillator and a microcontroller software algorithm
eliminate the requirement for a space and cost consuming
external crystal.
The AMIS-70020 is a timer IC that measures the duration of
power failures of up to five hours. The AMIS-70020 starts
and stops counting automatically as it is triggered by the
voltage of the input signal VCC. When VCC gets lower than
the reference signal VDD - VTH, a power cut-off is flagged
and the AMIS-70020 starts counting. During the counting
phase the AMIS-70020 is powered by an external capacitor
or by a primary battery and consequently operates
independently of an external power supply. Due to the low
power design of the AMIS-70020, the device can count the
full scale autonomously using the energy stored in a 10mF
capacitor.
Typical applications are those sensitive to power failures
that do not have a built-in UPS function. Examples are:
• Power inverters/Motordrivers/Soft starters
• Accurate I2t protection possible even after power loss
• Thermal protection devices for electrical motors
without integrated thermistor
• Motor controllers for electrical motors without
integrated thermistor
• Process control
• Chemical processes
• Industrial mixers
• Mixing reactors
As soon as VCC comes up again counting stops. The value
of the counter is shifted to the digital Q_OUT output pin
and is communicated to a microprocessor. After shifting the
full counted value, the internal RC-oscillator signal is put on
the Q_OUT output pin. Using this data the microcontroller
can calculate the duration of the power failure.
The internal power management circuit manages the
recharge of the external buffer capacitor.
2.0 Key Features
• Built-in 1kHz oscillator
• No external oscillator required
• Frequency of oscillator can be read by an external
microcontroller
• Accurate time measurement possible using software
calibration algorithm
• 2-wire interface with standard I/O pins of a
microcontroller
• Operating temperature -10~85˚C
• 150 mils SO8 package
• Few external components
• Easy design-in due to a user friendly application board
• Measures the time elapsed during a power failure
• Measures up to five hours
• 1 second resolution (RC oscillator/1024)
• Autonomous operation during power failure
• Auto switching to backup power
• Auto counter-start/stop function
• Maintenance free buffer capacitor
- 6 hours back-up with 10mF
- Capacitor recharge management built in (no external
diode needed)
• Li-button cell
- CR1220 (35mAh) supports up to 10 years in a typical
application
• Low current consumption <1µA
3.0 Ordering Information
Ordering Code
Package
Temp. Range
AMIS-70020
SO8
-10°C…-85°C
Ordering Code
EVK-70020
Evaluation kit
For sample requests contact your local sales representative
at www.amis.com/sales.
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1
AMIS-70020 Power Failure Elapsed Time Counter
Data Sheet
4.0 Block Diagram
CUT_OFF Test
VCC
1
0
m3
1
CUT_OFF
8
Test_Detect
CUT_OFF
Switch
3
COMPARATOR
VDD
2
POR
OUT_PORB
CUT_OFF_CMD
C
CONTROL
Oscillator CLK_1K
1 kHz
0
Divider
(10 bits)
m1
1
0
m2
1
0
m0
Q14_OUT
1
Register/Counter
(15 bits)
Q_OUT
5
EN0
Uc_Clk
UC_CLK_IN
Current_source
6
CLK_1S
7
Clk
4
VSS
5.0 Packaging
The AMIS-70020 is packaged in a 150mils SO8. Please visit
http://www.amis.com/pdf/soic.pdf for detailed mechanical
information.
Pinout
8
1
VCC
Uc_Clk
5
4
VSS
Clk
6
3
Test_Out
CUT_OFF
AMIS70020
7
2
VDD
Test
Q_Out
Pad Description
Pad No.
1
2
3
4
5
6
Name
VCC
VDD
CUT_OFF
VSS
Q_OUT
Uc_Clk
Type
Power
Power
Digital Output
Power
Digital Output
Digital Input
7
8
Clk
Test
Digital Output
Digital Input
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Comment
System power that is monitored
Back-up power
Not connected, test purpose only
Ground
Shift register output (CMOS output buffer 2mA)
CLK from microcontroller (Schmitt trigger input); an internal pull down (100KΩ) is
connected on the pin
Internal oscillator/1024 (1Hz) (CMOS output buffer 2mA)
For normal operation: connect to GND
2
AMIS-70020 Power Failure Elapsed Time Counter
Data Sheet
6.0 Application Diagram
Supply
5V
100nF
8
1
VCC
Test
7
2
10 mF VDD
MICRO
Clk
<
6
3
AMIS70020
CUT_OFF
Uc_Clk
4
5
>
Q_Out
VSS
The power supplies of the chip need to be properly
decoupled. This means that at least one external capacitor
CDD must be connected in between VSS and VCC.
Typical External Components
Component
Capacitor
Capacitor 1
Li Battery 1, 2
Function
Filter
Backup power supply
Backup power supply
Typical Value
Tol
100
+- 20%
10
+- 10%
CR1220 (35mAh)
Unit
nF
mF
1) Either a buffer capacitor of a Li-battery is
selected as a backup power supply.
2) In case a Li-battery is used as a backup
power supply a diode is must be placed
between the AMIS-70020 and the battery
to disable the charging feature.
7.0 Electrical and Environmental Ratings
Operating Ranges
Operation outside the operating ranges for extended
periods may affect device reliability. Total cumulative dwell
time above the maximum operating rating for power supply
or temperature must be less than 100 hours.
This section defines the limits for functional operation and
parametric characteristics of the device as described
elsewhere in this document. Note that functionality of the
IC outside the operating ranges is not guaranteed.
Symbol
VCC
VDD
Tamb
Tj
Cla
VIH
VIL
VOH
VOL
Description
Power supply voltage
Power supply voltage
Ambient temperature under bias
Junction temperature
Load capacitance on outputs
Digital input levels
Min
4.5
2
-10
Digital output levels
2.5
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Max
5.5
5.5
85
135
70
70% VDD
3
Unit
V
V
°C
°C
pF
V
30%VDD V
V
0.4
V
Input operating range of digital
IO’s 0-VDD
Output operating range of digital
IO’s 0-VDD
AMIS-70020 Power Failure Elapsed Time Counter
Data Sheet
Absolute Maximum Ratings
Stresses above those listed in this clause may cause
immediate and permanent device failure. It is not implied
that more than one of these conditions can be applied
simultaneously.
Symbol
VCC
VDDmr
Tamb,mr
Tj,mr
VIH
VIL
Description
Power supply voltage
Power supply voltage
Ambient temperature under bias
Junction temperature
Digital input levels
Min
-0.3
-0.3
-10
Max
7
7
85
150
VDD + 0.3
VDD – 0.3
Unit
V
V
°C
°C
V
V
Electrical Overstress Immunity
Latch-up immunity:
(2) Static latch-up protection level is 100mA at 25°C when
tested according to EIA/JESD78.
Electrostatic discharges on component level:
(1) The device withstands 2000V Human Body Model ESD
pulses when tested according to MIL STD 883 method
3015.5 (pin combination 2).
8.0 Detailed Electrical and Functional Description
Digital Interface
An internal pull down resistor is connected to the pin
Q_OUT, in order to avoid the parasitic shift of the counting
register.
The digital interface with a microcontroller can be made by
means of only two digital connections. The first is the clock
signal to be applied to the AMIS-70020 UC_CLK pin and
the second is the data line to be read by the microcontroller
from the Q_OUT pin. After a POR or after a power failure
(CUT_OFF) the 15 bit shift register is loaded with the
counter value and connected to the Q_OUT pin. The most
significant bit, MSB is already present and can be read at
the Q_OUT pin. Applying clocks at a maximum rate of
10MHz on UC_CLK will shift out the remaining counter bits.
After the fifteenth clock, the internal oscillator frequency
will be connected to the Q_OUT pin as a running clock
signal. By measuring the period of this signal, the time a
cut-off was present can be calculated by the
microcontroller.
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If VCC is powered up, a third optional pin – CLK - gives the
counter clock signal of about 1Hz. This clock is the internal
oscillator, divided by 1024 and can also be used to calibrate
the application.
Connections made with the microcontroller are separated
by level shifters. When in power failure mode, the inputs of
the AMIS-70020 are fixed to zero state. This will prevent
unwanted current leaking.
4
AMIS-70020 Power Failure Elapsed Time Counter
Timing Diagram
Flowchart
The flowchart depicts the operation of the AMIS-70020 in case
VCC gets smaller than VDD-VTH. After this flow has been
finished the buffer capacitor is recharged and the timer IC is
ready for a new cycle.
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5
Data Sheet
AMIS-70020 Power Failure Elapsed Time Counter
Data Sheet
Description of the Main Building Blocks
Oscillator
frequency. This can be done since the oscillator output
frequency can be measured by the microcontroller on the
Q_out pin after the measured counter value has been
shifted out the register.
The AMIS-70020 integrates an oscillator that functions
without any external components. The maximum accuracy
of the time measurement can only be obtained if the
measured time is calibrated with the actual oscillator
Symbol
Fosc
Description
Absolute frequency at ambient
Min
0.5
Typ
0.9
Max
1.9
Unit
kHz
Typ
1.4
Max
1.75
Unit
V
Comparator
When VCC < VDD – VTH, the comparator output
(CUT_OFF) is commuted. CUT_OFF signal is used by the
digital control to put the circuit in cut_off mode.
Symbol
VTH
Description
VDD-VCC threshold
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Min
0.75
6
AMIS-70020 Power Failure Elapsed Time Counter
Power on Reset
Symbol
Vpor
THreset
TLreset
Min
Typ
Max
1.65
2.25
3.08
Value not testable
Value not testable
Unit
V
Cut_off Switch
It is controlled by cut_off_ctrl when the comparator and
filter have detected the loss of VCC, in this case the switch
is OFF.
Symbol
Ron
Description
Resistance ON of the switch
Min
250
Typ
Max
500
Unit
Ω
Description
Min
DC current in cut_off mode
0.1
No load at the pin Test_OUT, Q_OUT
Typ
Max
Unit
0.5
1
µA
Current Consumption
Symbol
IDD
Revision Number
Version 1.1
Changes on page
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Data Sheet
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