CS5509
Single-supply, 16-bit A/D Converter
Description
Features
Delta-sigma A/D Converter
-
16-bit, No Missing Codes
-
Linearity Error: ±0.0015%FS
The CS5509 is a single-supply, 16-bit, serial-output
CMOS A/D converter. The CS5509 uses charge-balanced (delta-sigma) techniques to provide low-cost,
high-resolution measurements at output word rates up to
200 samples per second.
Differential Input
-
Pin-selectable Unipolar/Bipolar Ranges
-
Common Mode Rejection
105 dB @ dc
120 dB @ 50, 60 Hz
The on-chip digital filter offers superior line rejection at
50Hz and 60Hz when the device is operated from a
32.768 kHz clock (output word rate = 20 Sps).
The CS5509 has on-chip self-calibration circuitry which
can be initiated at any time or temperature to ensure
minimum offset and full-scale errors.
Either 5V or 3.3V Digital Interface
On-chip Self-calibration Circuitry
Output Update Rates up to 200/second
Ultra Low Power: 1.7 mW
Low power, high resolution, and small package size
make the CS5509 an ideal solution for loop-powered
transmitters, panel meters, weigh scales, and battery
powered instruments.
ORDERING INFORMATION
CS5509-ASZ -40 °C to +85 °C
16-pin SOIC Lead Free
I
VREF+
9
VREF10
VA+
GND
VD+
11
12
13
1
AIN+
AIN-
7
8
Differential
4th order
delta-sigma
modulator
Serial
Interface
Logic
Digital
Filter
SCLK
15
SDATA
16
DRDY
3
6
Calibration µC
Calibration
SRAM
CAL
BP/UP
OSC
2
CONV
http://www.cirrus.com
CS
14
Copyright Cirrus Logic, Inc. 2009
(All Rights Reserved)
4
XIN
5
XOUT
SEP ‘09
DS125F3
1
CS5509
ANALOG CHARACTERISTICS (TA = 25 °C; VA+ = 5V ±5%; VD+ = 3.3V ±5%; VREF+ = 2.5V,
VREF- = 0V; fCLK = 32.768 kHz; Bipolar Mode; Rsource = 40 Ω with a 10 nF to GND at AIN; AIN- = 2.5V; unless otherwise specified.) (Notes 1 and 2)
Parameter*
Min
Typ
Max
Unit
-
0.0015
0.0015
0.0015
0.005
0.003
0.003
0.003
0.0125
± %FS
± %FS
± %FS
± %FS
-
±0.25
±0.5
LSB
Accuracy
Linearity Error
fCLK = 32.768 kHz
fCLK = 165 kHz
fCLK = 247.5 kHz
fCLK = 330 kHz
Differential Nonlinearity
Full-scale Error
(Note 3)
-
±0.25
±2
LSB
Full-scale Drift
(Note 4)
-
±0.5
-
LSB
Unipolar Offset
(Note 3)
-
±0.5
±2
LSB
Unipolar Offset Drift
(Note 4)
-
±0.5
-
LSB
Bipolar Offset
(Note 3)
-
±0.25
±1
LSB
Bipolar Offset Drift
(Note 4)
-
±0.25
-
LSB
-
0.16
-
LSBrms
-
0 to +2.5
±2.5
-
V
V
120
105
-
-
dB
dB
-
15
-
pF
(Note 1)
-
5
-
nA
ITotal
IAnalog
IDigital
-
350
300
60
450
-
µA
µA
µA
(Note 7)
-
1.7
2.25
mW
-
80
-
dB
Noise (Referred to Output)
Analog Input
Analog Input Range
Common Mode Rejection
fCLK = 32.768 kHz
Unipolar
Bipolar
dc
50, 60 Hz
(Notes 5 and 6)
(Note 2)
Input Capacitance
DC Bias Current
Power Supplies
DC Power Supply Currents
Power Dissipation
Power Supply Rejection
Notes: 1. Both source resistance and shunt capacitance are critical in determining the CS5509's source
impedance requirements. Refer to the text section Analog Input Impedance Considerations.
2. Specifications guaranteed by design, characterization and/or test.
3. Applies after calibration at the temperature of interest.
4. Total drift over the specified temperature range since calibration at power-up at 25 °C.
5. The input is differential. Therefore, GND ≤ Signal + Common Mode Voltage ≤ VA+.
6. The CS5509 can accept input voltages up to the VA+ analog supply. In unipolar mode the CS5509 will
output all 1's if the dc input magnitude ((AIN+) - (AIN-)) exceeds ((VREF+) - (VREF-)) and will output all
0's if the input becomes more negative than 0 Volts. In bipolar mode the CS5509 will output all 1's if the
dc input magnitude ((AIN+) - (AIN-)) exceeds ((VREF+) - (VREF-)) and will output all 0's if the input
becomes more negative in magnitude than -((VREF+) - (VREF-)).
7. All outputs unloaded. All inputs CMOS levels.
* Refer to the Specification Definitions immediately following the Pin Description Section.
2
DS125F3
CS5509
DYNAMIC CHARACTERISTICS
Parameter
Symbol
Ratio
Unit
Modulator Sampling Frequency
fs
fclk/2
Hz
Output Update Rate (CONV = 1)
fout
fclk/1622
Hz
Filter Corner Frequency
f-3dB
fclk/1928
Hz
ts
1/fout
s
Settling Time to 1/2 LSB (FS Step)
5V DIGITAL CHARACTERISTICS
(TA = 25 °C; VA+, VD+ = 5V ±5%; GND = 0) (Notes 2 and 8)
Parameter
Symbol
Min
Typ
Max
Unit
XIN
All Pins Except XIN
VIH
3.5
2.0
-
-
V
V
XIN
All Pins Except XIN
VIL
-
-
1.5
0.8
V
V
High-level Output Voltage
(Note 9)
VOH
(VD+) -1.0
-
-
V
Low-level Output Voiltage
Iout = 1.6 mA
VOL
-
-
0.4
V
Input Leakage Current
Iin
-
±1
±10
µA
3-State Leakage Current
IOZ
-
-
±10
µA
Digital Output Pin Capacitance
Cout
-
9
-
pF
High-level Input Voltage
Low-level Input Voltage
Notes: 8. All measurements are performed under static conditions.
9. Iout = -100 µA. This guarantees the ability to drive one TTL load. (VOH = 2.4 V at Iout = -40 µA).
3.3V DIGITAL CHARACTERISTICS
(TA = 25 °C; VA+ = 5V ±5%; VD+ = 3.3V ±5%; GND = 0)
(Notes 2 and 8)
Parameter
Symbol
Min
Typ
Max
Unit
XIN
All Pins Except XIN
VIH
0.7 VD+
0.6 VD+
-
-
V
V
XIN
All Pins Except XIN
VIL
-
-
0.3 VD+
0.16 VD+
V
V
High-level Output Voltage
(Note 9)
VOH
(VD+) -0.3
-
-
V
Low-level Output Voltage
Iout = 1.6 mA
VOL
-
-
0.3
V
Input Leakage Current
Iin
-
±1
±10
µA
3-state Leakage Current
IOZ
-
-
±10
µA
Digital Output Pin Capacitance
Cout
-
9
-
pF
High-level Input Voltage
Low-level Input Voltage
Specifications are subject to change without notice
DS125F3
3
CS5509
5V SWITCHING CHARACTERISTICS (TA = 25 °C; VA+, VD+ = 5V ±5%;
Input Levels: Logic 0 = 0V, Logic 1 = VD+; CL = 50 pF) (Note 2)
Parameter
Master Clock Frequency
Internal Oscillator
External Clock
Symbol
Min
Typ
Max
Unit
XIN
fclk
30.0
30
32.768
-
53.0
330
kHz
kHz
Master Clock Duty Cycle
Rise Times
Fall Time
Any Digital Input
Any Digital Output
(Note 10)
Any Digital Input
Any Digital Output
(Note 10)
40
-
60
%
trise
-
50
1.0
-
µs
ns
tfall
-
20
1.0
-
µs
ns
Start-Up
Power-On Reset Period
(Note 11)
tres
-
10
-
ms
Oscillator Start-up Time
XTAL = 32.768 kHz (Note 12)
tosu
-
500
-
ms
(Note 13)
twup
-
1800/fclk
-
s
(Note 14)
tccw
100
-
-
ns
CONV and CAL High to Start of Calibration
tscl
-
-
2/fclk+200
ns
Start of Calibration to End of Calibration
tcal
-
3246/fclk
-
s
CONV Pulse Width
tcpw
100
-
-
ns
CONV High to Start of Conversion
tscn
-
-
2/fclk+200
ns
Set Up Time
BP/UP stable prior to DRDY falling
tbus
82/fclk
-
-
s
BP/UP stable after DRDY falls
tbuh
0
-
-
ns
tcon
-
1624/fclk
-
s
Wake-up Period
Calibration
CONV Pulse Width (CAL = 1)
Conversion
Hold Time
Start of Conversion to End of Conversion
(Note 15)
Notes: 10. Specified using 10% and 90% points on waveform of interest.
11. An internal power-on-reset is activated whenever power is applied to the device.
12. Oscillator start-up time varies with the crystal parameters. This specification does not apply when using
an external clock source.
13. The wake-up period begins once the oscillator starts; or when using an external fclk, after the power-on
reset time elapses.
14. Calibration can also be initiated by pulsing CAL high while CONV=1.
15. Conversion time will be 1622/fclk if CONV remains high continuously.
4
DS125F3
CS5509
3.3V SWITCHING CHARACTERISTICS (TA = 25 °C; VA+ = 5V ±5%; VD+ = 3.3V ±5%; Input
Levels: Logic 0 = 0V, Logic 1 = VD+; CL = 50 pF) (Note 2)
Parameter
Master Clock Frequency
Internal Oscillator
External Clock
Symbol
Min
Typ
Max
Unit
XIN
fclk
30.0
30
32.768
-
53.0
330
kHz
kHz
Master Clock Duty Cycle
Rise Times
Fall Time
Any Digital Input
Any Digital Output
(Note 10)
Any Digital Input
Any Digital Output
(Note 10)
40
-
60
%
trise
-
50
1.0
-
µs
ns
tfall
-
20
1.0
-
µs
ns
Start-Up
Power-On Reset Period
(Note 11)
tres
-
10
-
ms
Oscillator Start-up Time
XTAL = 32.768 kHz (Note 12)
tosu
-
500
-
ms
(Note 13)
twup
-
1800/fclk
-
s
(Note 14)
tccw
100
-
-
ns
CONV and CAL High to Start of Calibration
tscl
-
-
2/fclk+200
ns
Start of Calibration to End of Calibration
tcal
-
3246/fclk
-
s
CONV Pulse Width
tcpw
100
-
-
ns
CONV High to Start of Conversion
tscn
-
-
2/fclk+200
ns
Set Up Time
BP/UP stable prior to DRDY falling
tbus
82/fclk
-
-
s
BP/UP stable after DRDY falls
tbuh
0
-
-
ns
tcon
-
1624/fclk
-
s
Wake-up Period
Calibration
CONV Pulse Width (CAL = 1)
Conversion
Hold Time
Start of Conversion to End of Conversion
DS125F3
(Note 15)
5
CS5509
XIN
XIN/2
CAL
t ccw
CONV
t scl
STATE
t cal
Standby
Calibration
Standby
Figure 1. Calibration Timing (Not to Scale)
XIN
XIN/2
CONV
t cpw
DRDY
BP/UP
t scn
STATE
Standby
t con
Conversion
t bus
t buh
Standby
Figure 2. Conversion Timing (Not to Scale)
6
DS125F3
CS5509
5V SWITCHING CHARACTERISTICS
(TA = 25 °C; VA+, VD+ = 5V ±5%; Input Levels: Logic 0 =
0V, Logic 1 = VD+; CL = 50 pF) (Note 2)
Parameter
Symbol
Min
Typ
Max
Unit
fsclk
0
-
2.5
MHz
Pulse Width High
Pulse Width Low
tph
tpl
200
200
-
-
ns
ns
CS Low to data valid (Note 16)
tcsd
-
60
200
ns
tdd
-
150
310
ns
tfd1
tfd2
-
60
160
150
300
ns
ns
Serial Clock
Serial Clock
Access Time
Maximum Delay Time
SCLK falling to new SDATA bit
Output Float Delay
(Note 17)
CS High to output Hi-Z (Note 18)
SCLK falling to Hi-Z
Notes: 16. If CS is activated asynchronously to DRDY, CS will not be recognized if it occurs when DRDY is high
for 2 clock cycles. The propagation delay time may be as great as 2 fclk cycles plus 200 ns. To guarantee
proper clocking of SDATA when using asynchronous CS, SCLK(i) should not be taken high sooner than
2 fclk + 200 ns after CS goes low.
17. SDATA transitions on the falling edge of SCLK. Note that a rising SCLK must occur to enable the serial
port shifting mechanism before falling edges can be recognized.
18. If CS is returned high before all data bits are output, the SDATA output will complete the current data
bit and then go to high impedance.
3.3V SWITCHING CHARACTERISTICS (TA = 25 °C; VA+ = 5V ±5%; VD+ = 3.3V ±5%; Input
Levels: Logic 0 = 0V, Logic 1 = VD+; CL = 50 pF) (Note 2)
Parameter
Symbol
Min
Typ
Max
Unit
fsclk
0
-
1.25
MHz
Pulse Width High
Pulse Width Low
tph
tpl
200
200
-
-
ns
ns
CS Low to data valid (Note 16)
tcsd
-
100
200
ns
tdd
-
400
600
ns
tfd1
tfd2
-
70
320
150
500
ns
ns
Serial Clock
Serial Clock
Access Time
Maximum Delay Time
SCLK falling to new SDATA bit
Output Float Delay
DS125F3
(Note 17)
CS High to output Hi-Z (Note 18)
SCLK falling to Hi-Z
7
CS5509
DRDY
CS
t fd1
t csd
SDATA(o)
Hi-Z
MSB
t dd
MSB-1
MSB-2
SCLK(i)
DRDY
CS
t csd
SDATA(o)
Hi-Z
MSB
t dd
MSB-1
LSB+2
t ph
LSB+1
LSB
tfd2
SCLK(i)
t pl
Figure 3. Timing Relationships (Not to Scale)
8
DS125F3
CS5509
RECOMMENDED OPERATING CONDITIONS
Parameter
DC Power Supplies
Symbol
Min
Typ
Max
Unit
VD+
VA+
3.15
4.75
5.0
5.0
5.5
5.5
V
V
(Note 20)
(VREF+) (VREF-)
1.0
2.5
3.6
V
(Note 6)
Unipolar
Bipolar
VAIN
VAIN
0
-((VREF+) - (VREF-))
-
(VREF+) - (VREF-)
(VREF+) - (VREF-)
V
V
Positive Digital
Positive Analog
Analog Reference Voltage
Analog Input Voltage
(DGND = 0V) (Note 19)
Notes: 19. All voltages with respect to ground.
20. The CS5509 can be operated with a reference voltage as low as 100 mV; but with a corresponding
reduction in noise-free resolution. The common mode voltage of the voltage reference may be any value
as long as +VREF and -VREF remain inside the supply values of VA+ and GND.
ABSOLUTE MAXIMUM RATINGS*
Parameter
DC Power Supplies
Ground
Positive Digital
Positive Analog
Input Current, Any Pin Except Supplies
Symbol
Min
Typ
Max
Unit
GND
VD+
VA+
-0.3
-0.3
-0.3
-
(VD+)-0.3
6.0
6.0
V
V
V
Iin
-
-
±10
mA
Iout
-
-
±25
mA
(Note 21)
(Note 22)
(Notes 23 and 24)
Output Current
Power Dissipation (Total)
-
-
500
mW
VINA
-0.3
-
(VA+)+0.3
V
VIND
-0.3
-
(VD+)+0.3
V
Ambient Operating Temperature
TA
-40
-
85
°C
Storage Temperature
Tstg
-65
-
150
°C
Analog Input Voltage
(Note 25)
AIN and VREF pins
Digital Input Voltage
Notes: 21. No pin should go more positive than (VA+) + 0.3 V.
22. VD+ must always be less than (VA+) + 0.3 V, and can never exceed +6.0 V.
23. Applies to all pins including continuous overvoltage conditions at the analog input (AIN) pin.
24. Transient currents of up to 100 mA will not cause SCR latch-up. Maximum input current for a power
supply pin is ± 50 mA.
25. Total power dissipation, including all input currents and output currents.
*WARNING:Operation at or beyond these limits may result in permanent damage to the device.
Normal operation is not guaranteed at these extremes.
DS125F3
9
CS5509
GENERAL DESCRIPTION
Calibration
The CS5509 is a low power, 16-bit, monolithic
CMOS A/D converter designed specifically for
measurement of dc signals. The CS5509 includes a
delta-sigma charge-balance converter, a voltage
reference, a calibration microcontroller with
SRAM, a digital filter and a serial interface.
After the initial application of power, the CS5509
must enter the calibration state prior to performing
accurate conversions. During calibration, the chip
executes a two-step process. The device first performs an offset calibration and then follows this
with a gain calibration. The two calibration steps
determine the zero reference point and the full scale
reference point of the converter's transfer function.
From these points it calibrates the zero point and a
gain slope to be used to properly scale the output
digital codes when doing conversions.
The CS5509 is optimized to operate from a 32.768
kHz crystal but can be driven by an external clock
whose frequency is between 30kHz and 330kHz.
When the digital filter is operated with a 32.768
kHz clock, the filter has zeros precisely at 50 and
60 Hz line frequencies and multiples thereof.
The CS5509 uses a "start convert" command to
start a convolution cycle on the digital filter. Once
the filter cycle is completed, the output port is updated.When operated with a 32.768kHz clock the
ADC converts and updates its output port at 20
samples/sec.The output port operates in a synchronous externally-clocked interface format.
THEORY OF OPERATION
Basic Converter Operation
The CS5509 A/D converter has three operating
states. These are stand-by, calibration, and conversion. When power is first applied, an internal power-on reset delay of about 10 ms resets all of the
logic in the device. The oscillator must then begin
oscillating before the device can be considered
functional. After the power-on reset is applied, the
device enters the wake-up period for 1800 clock
cycles after clock is present. This allows the deltasigma modulator and other circuitry (which are operating with very low currents) to reach a stable
bias condition prior to entering into either the calibration or conversion states. During the 1800 cycle
wake-up period, the device can accept an input
command. Execution of this command will not occur until the complete wake-up period elapses. If
no command is given, the device enters the standby
state.
10
The calibration state is entered whenever the CAL
and CONV pins are high at the same time. The state
of the CAL and CONV pins at power-on are recognized as commands, but will not be executed until
the end of the 1800 clock cycle wake-up period.
If CAL and CONV become active (high) during the
1800 clock cycle wake-up time, the converter will
wait until the wake-up period elapses before executing the calibration. If the wake-up time has
elapsed, the converter will be in the standby mode
waiting for instruction and will enter the calibration
cycle immediately if CAL and CONV become active. The calibration lasts for 3246 clock cycles.
Calibration coefficients are then retained in the
SRAM (static RAM) for use during conversion.
The state of BP/UP is ignored during calibration
but should remain stable throughout the calibration
period to minimize noise.
When conversions are performed in unipolar mode
or in bipolar mode, the converter uses the same calibration factors to compute the digital output code.
The only difference is that in bipolar mode the onchip microcontroller offsets the computed output
word by a code value of 8000H. This means that the
bipolar measurement range is not calibrated from
full scale positive to full scale negative. Instead it is
calibrated from the bipolar zero scale point to full
scale positive. The slope factor is then extended below bipolar zero to accommodate the negative inDS125F3
CS5509
put signals. The converter can be used to convert
both unipolar and bipolar signals by changing the
BP/UP pin. Recalibration is not required when
switching between unipolar and bipolar modes.
At the end of the calibration cycle, the on-chip microcontroller checks the logic state of the CONV
signal. If the CONV input is low the device will enter the standby mode where it waits for further instruction. If the CONV signal is high at the end of
the calibration cycle, the converter will enter the
conversion state and perform a conversion on the
input channel. The CAL signal can be returned low
any time after calibration is initiated. CONV can
also be returned low, but it should never be taken
low and then taken back high until the calibration
period has ended and the converter is in the standby
state. If CONV is taken low and then high again
with CAL high while the converter is calibrating,
the device will interrupt the current calibration cycle and start a new one. If CAL is taken low and
CONV is taken low and then high during calibration, the calibration cycle will continue as the conversion command is disregarded. The state of
BP/UP is not important during calibrations.
If an "end of calibration" signal is desired, pulse the
CAL signal high while leaving the CONV signal
high continuously. Once the calibration is completed, a conversion will be performed. At the end of
the conversion, DRDY will fall to indicate the first
valid conversion after the calibration has been
completed.
Conversion
The conversion state can be entered at the end of
the calibration cycle, or whenever the converter is
idle in the standby mode. If CONV is taken high to
initiate a calibration cycle ( CAL also high), and remains high until the calibration cycle is completed
(CAL is taken low after CONV transitions high),
the converter will begin a conversion upon completion of the calibration period.
DS125F3
The BP/UP pin is not a latched input. The BP/UP
pin controls how the output word from the digital
filter is processed. In bipolar mode the output word
computed by the digital filter is offset by 8000H
(see Understanding Converter Calibration). BP/UP
can be changed after a conversion is started as long
as it is stable for 82 clock cycles of the conversion
period prior to DRDY falling. If one wishes to intermix measurement of bipolar and unipolar signals
on various input signals, it is best to switch the
BP/UP pin immediately after DRDY falls and
leave BP/UP stable until DRDY falls again.
The digital filter in the CS5509 has a Finite Impulse Response and is designed to settle to full accuracy in one conversion time.
If CONV is left high, the CS5509 will perform continuous conversions. The conversion time will be
1622 clock cycles. If conversion is initiated from
the standby state, there may be up to two XIN clock
cycles of uncertainty as to when conversion actually begins. This is because the internal logic operates at one half the external clock rate and the exact
phase of the internal clock may be 180° out of
phase relative to the XIN clock. When a new conversion is initiated from the standby state, it will
take up to two XIN clock cycles to begin. Actual
conversion will use 1624 clock cycles before
DRDY goes low to indicate that the serial port has
been updated. See the Serial Interface Logic section of the data sheet for information on reading
data from the serial port.
In the event the A/D conversion command (CONV
going positive) is issued during the conversion
state, the current conversion will be terminated and
a new conversion will be initiated.
Voltage Reference
The CS5509 uses a differential voltage reference
input. The positive input is VREF+ and the negative input is VREF-. The voltage between VREF+
and VREF- can range from 1 volt minimum to 3.6
volts maximum. The gain slope will track changes
11
CS5509
in the reference without recalibration, accommodating ratiometric applications.
Analog Input Range
The analog input range is set by the magnitude of
the voltage between the VREF+ and VREF- pins.
In unipolar mode the input range will equal the
magnitude of the voltage reference. In bipolar
mode the input voltage range will equate to plus
and minus the magnitude of the voltage reference.
While the voltage reference can be as great as 3.6
volts, its common mode voltage can be any value as
long as the reference inputs VREF+ and VREFstay within the supply voltages VA+ and GND.
The differential input voltage can also have any
common mode value as long as the maximum signal magnitude stays within the supply voltages.
The A/D converter is intended to measure dc or low
frequency inputs. It is designed to yield accurate
conversions even with noise exceeding the input
voltage range as long as the spectral components of
this noise will be filtered out by the digital filter.
For example, with a 3.0 volt reference in unipolar
mode, the converter will accurately convert an input dc signal up to 3.0volts with up to 15% overrange for 60Hz noise. A 3.0volt dc signal could
have a 60Hz component which is 0.5volts above
the maximum input of 3.0 (3.5 volts peak; 3.0 volts
dc plus 0.5 volts peak noise) and still accurately
convert the input signal (XIN = 32.768 kHz). This
assumes that the signal plus noise amplitude stays
within the supply voltages.
The CS5509 converters output data in binary format when converting unipolar signals and in offset
binary format when converting bipolar signals. Table 1 outlines the output coding for both unipolar
and bipolar measurement modes.
Converter Performance
The CS5509 A/D converter has excellent linearity
performance. Calibration minimizes the errors in
12
Unipolar Input
Voltage
> (VREF - 1.5 LSB)
VREF - 1.5 LSB
Output
Codes
VREF/2 - 0.5 LSB
8000-------------7FFF
-0.5 LSB
+0.5 LSB
0001
------------0000
0000
-VREF + 0.5 LSB
FFFF
FFFF
---------------FFFE
Bipolar Input
Voltage
> (VREF - 1.5 LSB)
VREF - 1.5 LSB
< (-VREF + 0.5 LSB)
< (+0.5 LSB)
Note: Table excludes common mode voltage on the
signal and reference inputs.
Table 1. Output Coding
offset and gain. The CS5509 device has no missing
code performance to 16-bits. Figure4 illustrates the
DNL of the CS5509. The converter achieves Common Mode Rejection (CMR) at dc of 105dB typical, and CMR at 50 and 60Hz of 120dB typical.
The CS5509 can experience some drift as temperature changes. The CS5509 uses chopper-stabilized
techniques to minimize drift. Measurement errors
due to offset or gain drift can be eliminated at any
time by recalibrating the converter.
Analog Input Impedance Considerations
The analog input of the CS5509 can be modeled as
illustrated in Figure 5. Capacitors (15 pF each) are
used to dynamically sample each of the inputs
(AIN+ and AIN-). Every half XIN cycle the switch
alternately connects the capacitor to the output of
the buffer and then directly to the AIN pin. Whenever the sample capacitor is switched from the output of the buffer to the AIN pin, a small packet of
charge (a dynamic demand of current) is required
from the input source to settle the voltage of the
sample capacitor to its final value. The voltage on
the output of the buffer may differ up to 100 mV
from the actual input voltage due to the offset voltage of the buffer. Timing allows one half of a XIN
clock cycle for the voltage on the sample capacitor
to settle to its final value.
DS125F3
CS5509
Figure 4. CS5509 Differential Nonlinearity Plot
AIN+
V os ≤ 100 mV
+
-
AIN-
15 pF
Internal
Bias
Voltage
15 pF
V os ≤ 100 mV
+
-
Figure 5. Analog Input Model
An equation for the maximum acceptable source
resistance is derived.
–1
Rs max = ------------------------------------------------------------------------------------------------------------------------Ve
2XIN ( 15pF + C EXT ) ln --------------------------------------------------15pF ( 100mV )
V e + ------------------------------------15pF + C EXT
This equation assumes that the offset voltage of the
buffer is 100 mV, which is the worst case. The value of Ve is the maximum error voltage which is acceptable. CEXT is the combination of any external
or stray capacitance.
For a maximum error voltage (Ve) of 10 µV in the
CS5509 (1/4LSB at 16-bits), the above equation indicates that when operating from a 32.768 kHz
XIN, source resistances up to 110 kΩ are acceptable in the absence of external capacitance
(CEXT=0).
DS125F3
The VREF+ and VREF- inputs have nearly the
same structure as the AIN+ and AIN- inputs.
Therefore, the discussion on analog input impedance applies to the voltage reference inputs as well.
Digital Filter Characteristics
The digital filter in the CS5509 is the combination
of a comb filter and a low pass filter. The comb filter has zeros in its transfer function which are optimally placed to reject line interference frequencies
(50 and 60 Hz and their multiples) when the
CS5509 is clocked at 32.768 kHz. Figures 6, 7 and
8 illustrate the magnitude and phase characteristics
of the filter. Figure 6 illustrates the filter attenuation from dc to 260 Hz. At exactly 50, 60, 100, and
120 Hz the filter provides over 120 dB of rejection.
Table 2 indicates the filter attenuation for each of
the potential line interference frequencies when the
converter is operating with a 32.768 kHz clock.
The converter yields excellent attenuation of these
interference frequencies even if the fundamental
line frequency should vary ± 1% from its specified
frequency. The -3 dB corner frequency of the filter
when operating from a 32.768 kHz clock is 17 Hz.
Figure 8 illustrates that the phase characteristics of
the filter are precisely linear phase.
If the CS5509 is operated at a clock rate other than
32.768kHz, the filter characteristics, including the
comb filter zeros, will scale with the operating
clock frequency. Therefore, optimum rejection of
13
CS5509
0
180
X1 = 32.768kHz
X2 = 330.00kHz
-20
135
90
Phase (Degrees)
Attenuation (dB)
-40
-60
-80
-100
45
0
-45
-120
-90
-140
-135
XIN = 32.768 kHz
XIN = 32.768 kHz
-160
X1
0
X2
0
-180
40
80
120
160
200
240
402.83 805.66 1208.5 1611.3 2014.2 2416.9
0
5
10
15
20
25
30
35
40
45
50
Frequency (Hz)
Frequency (Hz)
Figure 8. Filter Phase Plot to 50 Hz
Figure 6. Filter Magnitude Plot to 260 Hz
0
Attenuation (dB)
-20
Frequency
(Hz)
Flatness
Frequency dB
1
-0.010
-40
2
-60
-80
-100
3
-0.041
-0.093
4
-0.166
5
-0.259
6
-0.374
7
-0.510
8
-0.667
9
-0.846
10
-1.047
17
-3.093
50
60
100
120
150
180
200
240
XIN = 32.768 kHz
-120
Frequency
(Hz)
125.6
50 ±1%
60 ±1%
100 ±1%
120 ±1%
150 ±1%
180 ±1%
200 ±1%
240 ±1%
126.7
145.7
136.0
118.4
132.9
102.5
108.4
Minimum
Attenuation
(dB)
55.5
58.4
62.2
68.4
74.9
87.9
94.0
104.4
Table 2. Filter Notch Attenuation (XIN = 32.768 kHz)
-140
0
5
10
15
20
25
30
35
40
45
50
Frequency (Hz)
Figure 7. Filter Magnitude Plot to 50 Hz
line frequency interference will occur with the
CS5509 running at 32.768kHz.
14
Notch
Depth
(dB)
Anti-Alias Considerations for Spectral
Measurement Applications
Input frequencies greater than one half the output
word rate (CONV = 1) may be aliased by the converter. To prevent this, input signals should be limited in frequency to no greater than one half the
output word rate of the converter (when CONV
=1). Frequencies close to the modulator sample rate
(XIN/2) and multiples thereof may also be aliased.
If the signal source includes spectral components
above one half the output word rate (when CONV
= 1) these components should be removed by
means of low-pass filtering prior to the A/D input
DS125F3
CS5509
to prevent aliasing. Spectral components greater
than one half the output word rate on the VREF inputs (VREF+ and VREF-) may also be aliased. Filtering of the reference voltage to remove these
spectral components from the reference voltage is
desirable.
Crystal Oscillator
The CS5509 is designed to be operated using a
32.768kHz "tuning fork" type crystal. One end of
the crystal should be connected to the XIN input.
The other end should be attached to XOUT. Short
lead lengths should be used to minimize stray capacitance.
Over the industrial temperature range (-40 to
+85 °C) the on-chip gate oscillator will oscillate
with other crystals in the range of 30kHz to 53 kHz.
The chip will operate with external clock frequencies from 30kHz to 330kHz over the industrial temperature range. The 32.768 kHz crystal is normally
specified as a time-keeping crystal with tight specifications for both initial frequency and for drift
over temperature. To maintain excellent frequency
stability, these crystals are specified only over limited operating temperature ranges (i.e. -10 °C to
+60 °C) by the manufacturers. Applications of
these crystals with the CS5509 does not require
tight initial tolerance or low tempco drift. Therefore, a lower cost crystal with looser initial tolerance and tempco will generally be adequate for use
with the CS5509. Also check with the manufacturer about wide temperature range application of
their standard crystals. Generally, even those crystals specified for limited temperature range will operate over much larger ranges if frequency stability
over temperature is not a requirement. The frequency stability can be as bad as ±3000 ppm over the
operating temperature range and still be typically
better than the line frequency (50 Hz or 60Hz) stability over cycle-to-cycle during the course of a
day.
DS125F3
Serial Interface Logic
The digital filter in the CS5509 takes 1624 clock
cycles to compute an output word once a conversion begins. At the end of the conversion cycle, the
filter will attempt to update the serial port. Two
clock cycles prior to the update DRDY will go
high. When DRDY goes high just prior to a port update it checks to see if the port is either empty or
unselected (CS = 1). If the port is empty or unselected, the digital filter will update the port with a
new output word. When new data is put into the
port DRDY will go low.
Reading Serial Data
SDATA is the output pin for the serial data. When
CS goes low after new data becomes available
(DRDY goes low), the SDATA pin comes out of
Hi-Z with the MSB data bit present. SCLK is the
input pin for the serial clock. If the MSB data bit is
on the SDATA pin, the first rising edge of SCLK
enables the shifting mechanism. This allows the
falling edges of SCLK to shift subsequent data bits
out of the port. Note that if the MSB data bit is output and the SCLK signal is high, the first falling
edge of SCLK will be ignored because the shifting
mechanism has not become activated. After the
first rising edge of SCLK, each subsequent falling
edge will shift out the serial data. Once the LSB is
present, the falling edge of SCLK will cause the
SDATA output to go to Hi-Z and DRDY to return
high. The serial port register will be updated with a
new data word upon the completion of another conversion if the serial port has been emptied, or if the
CS is inactive (high).
CS can be operated asynchronously to the DRDY
signal. The DRDY signal need not be monitored as
long as the CS signal is taken low for at least two
XIN clock cycles plus 200ns prior to SCLK being
toggled. This ensures that CS has gained control
over the serial port.
15
CS5509
Power Supplies and Grounding
The analog and digital supply pins to the CS5509
are brought out on separate pins to minimize noise
coupling between the analog and digital sections of
the chip. In the digital section of the chip the supply
current flows into the VD+ pin and out of the GND
pin. As a CMOS device, the CS5509 requires that
the supply voltage on the VA+ pin always be more
positive than the voltage on any other pin of the device. If this requirement is not met, the device can
latch-up or be damaged. In all circumstances the
VA+ voltage must remain more positive than the
VD+ or GND pins; VD+ must remain more positive than the GND pin.
16
Figure 9a illustrates the System Connection Diagram for the CS5509. Note that all supply pins are
bypassed with 0.1 µF capacitors and that the VD+
digital supply is derived from the VA+ supply. Figure 9b illustrates the CS5509 operating from a +5V
analog supply and +3.3V digital supply.
When using separate supplies for VA+ and VD+,
VA+ must be established first. VD+ should never
become more positive than VA+ under any operating condition. Remember to investigate transient
power-up conditions, when one power supply may
have a faster rise time.
DS125F3
CS5509
10Ω
+5V
Analog
Supply
0.1 µF
Optional
Clock
Source
0.1 µF
4
5
32.768 kHz
11
13
VA+
VD+
XIN
SCLK
XOUT
SDATA
14
15
Serial
Data
Interface
CS5509
7
Analog
Signal
8
AIN+
AINCS
CONV
+
Voltage
Reference
-
9
10
CAL
VREF+
BP/UP
DRDY
VREF-
1
2
3
6
Control
Logic
16
GND
12
Figure 9a. System Connection Diagram Using a Single Supply
DS125F3
17
CS5509
Note: VD+ must never be more positive than VA+
+5V
Analog
Supply
0.1 µF
Optional
Clock
Source
0.1 µF
4
5
32.768 kHz
11
13
VA+
VD+
XIN
SCLK
XOUT
SDATA
+3.3V to +5V
Digital
Supply
14
15
Serial
Data
Interface
CS5509
7
Analog
Signal
8
AIN+
AINCS
CONV
+
Voltage
Reference
-
9
10
CAL
VREF+
BP/UP
DRDY
VREF-
1
2
3
6
Control
Logic
16
GND
12
Figure 9b. System Connection Diagram Using Split Supplies
18
DS125F3
CS5509
PIN DESCRIPTIONS*
CHIP SELECT
CS
1
16
DRDY
DATA READY
CONVERT
CONV
2
15
SDATA
SERIAL DATA OUTPUT
CALIBRATE
CAL
3
14
SCLK
SERIAL CLOCK INPUT
CRYSTAL IN
XIN
4
13
VD+
POSITIVE DIGITAL POWER
CRYSTAL OUT
XOUT
5
12
GND
GROUND
BIPOLAR / UNIPOLAR
BP/UP
6
11
VA+
POSITIVE ANALOG POWER
DIFFERENTIAL ANALOG INPUT
AIN+
7
10
VREF-
VOLTAGE REFERENCE INPUT
DIFFERENTIAL ANALOG INPUT
AIN-
8
9
VREF+
VOLTAGE REFERENCE INPUT
* Pinout applies to both PDIP and SOIC
Clock Generator
XIN; XOUT - Crystal In; Crystal Out, Pins 4, 5.
A gate inside the chip is connected to these pins and can be used with a crystal to provide the
master clock for the device. Alternatively, an external (CMOS compatible) clock can be
supplied into the XIN pin to provide the master clock for the device. Loss of clock will put the
device into a lower powered state (approximately 70% power reduction).
Serial Output I/O
CS - Chip Select, Pin 1.
This input allows an external device to access the serial port.
DRDY - Data Ready, Pin 16.
Data Ready goes low at the end of a digital filter convolution cycle to indicate that a new
output word has been placed into the serial port. DRDY will return high after all data bits are
shifted out of the serial port or two master clock cycles before new data becomes available if
the CS pin is inactive (high).
SDATA - Serial Data Output, Pin 15.
SDATA is the output pin of the serial output port. Data from this pin will be output at a rate
determined by SCLK. Data is output MSB first and advances to the next data bit on the falling
edges of SCLK. SDATA will be in a high impedance state when not transmitting data.
SCLK - Serial Clock Input, Pin 14.
A clock signal on this pin determines the output rate of the data from the SDATA pin. This pin
must not be allowed to float.
DS125F3
19
CS5509
Control Input Pins
CAL - Calibrate, Pin 3.
When taken high the same time that the CONV pin is taken high the converter will perform a
self-calibration which includes calibration of the offset and gain scale factors in the converter.
CONV - Convert, Pin 2.
The CONV pin initiates a calibration cycle if it is taken from low to high while the CAL pin is
high, or it initiates a conversion if it is taken from low to high with the CAL pin low. If CONV
is held high (CAL low) the converter will do continuous conversions.
BP/UP - Bipolar/Unipolar, Pin 6.
The BP/UP pin selects the conversion mode of the converter. When high the converter will
convert bipolar input signals; when low it will convert unipolar input signals.
Measurement and Reference Inputs
AIN+, AIN- - Differential Analog Inputs, Pins 7, 8.
Analog differential inputs to the delta-sigma modulator.
VREF+, VREF- - Differential Voltage Reference Inputs, Pins 9, 10.
A differential voltage reference on these pins operates as the voltage reference for the
converter. The voltage between these pins can be any voltage between 1.0 and 3.6 volts.
Power Supply Connections
VA+ - Positive Analog Power, Pin 11.
Positive analog supply voltage. Nominally +5 volts.
VD+ - Positive Digital Power, Pin 13.
Positive digital supply voltage. Nominally +5 volts or +3.3 volts.
GND - Ground, Pin 12.
Ground.
20
DS125F3
CS5509
SPECIFICATION DEFINITIONS
Linearity Error
The deviation of a code from a straight line which connects the two endpoints of the A/D
Converter transfer function. One endpoint is located 1/2 LSB below the first code transition and
the other endpoint is located 1/2 LSB beyond the code transition to all ones. Units in percent of
full-scale.
Differential Nonlinearity
The deviation of a code's width from the ideal width. Units in LSBs.
Full Scale Error
The deviation of the last code transition from the ideal [{(VREF+) - (VREF-)} - LSB]. Units
are in LSBs.
Unipolar Offset
The deviation of the first code transition from the ideal ( LSB above the voltage on the AINpin.) when in unipolar mode (BP/UP low). Units are in LSBs.
Bipolar Offset
The deviation of the mid-scale transition (011...111 to 100...000) from the ideal ( LSB below
the voltage on the AIN- pin.) when in bipolar mode (BP/UP high). Units are in LSBs
DS125F3
21
CS5509
PACKAGE DIMENSIONS
INCHES
MIN NOM MAX
0.390 0.400 0.410
28
MILLIMETERS
MIN NOM MAX
9.91 10.16 10.41
12.45 12.70 12.95
14.99 15.24 15.50
17.53 17.78 18.03
DIM
MILLIMETERS
MIN NOM MAX
INCHES
MIN NOM MAX
pins
16
20
24
D
SOIC
A
A1
A2
E1 E
b
c
A2
e
22
b
A1
D
E
E1
A
µ
c
L
e
L
µ
0.490 0.500 0.510
0.590 0.600 0.610
0.690 0.700 0.710
2.41
0.127
2.54 2.67 0.095 0.100 0.105
0.300 0.005
0.012
2.29
2.41 2.54
0.090 0.095 0.100
0.33
0.46 0.51 0.013 0.018 0.020
0.203 0.280 0.381 0.008 0.011 0.015
see table above
10.11 10.41 10.67 0.398 0.410 0.420
7.42 7.49 7.57 0.292 0.295 0.298
1.14
0.41
1.27
-
0°
-
1.40 0.040 0.050 0.055
0.89 0.016
0.035
0°
8°
8°
DS125F3
CS5509
ENVIRONMENTAL, MANUFACTURING, & HANDLING INFORMATION
Model
CS5509-ASZ (lead free)
Peak Relfow Temp
MSL Rating*
Maximum Floor Life
260 °C
3
7 Days
* MSL (Moisture Sensitivity Level) as specified by IPC/JEDEC J-STD-020.
DS125F3
23
CS5509
REVISION HISTORY
Revision
Date
Changes
F1
Aug ‘97
First “final” release.
F2
Aug ‘05
Added lead-free device ordering info. Added legal notice. Added MSL data.
F3
Jul ‘09
Removed PDIP and leaded (Pb) devices from ordering information.
Contacting Cirrus Logic Support
For all product questions and inquiries contact a Cirrus Logic Sales Representative.
To find the one nearest to you go to www.cirrus.com
IMPORTANT NOTICE
Cirrus Logic, Inc. and its subsidiaries (“Cirrus”) believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided “AS IS” without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
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Cirrus Logic, Cirrus, and the Cirrus Logic logo designs are trademarks of Cirrus Logic, Inc. All other brand and product names in this document may be trademarks
or service marks of their respective owners.
24
DS125F3