Rev 1; 2/09
Dual Delta-Sigma Modulator and Encoder
General Description
The DS8102 is a stand-alone, dual-channel, delta-
sigma modulator that converts measurements from two
differential analog input pairs into a Manchester-encod-
ed output bit stream that can be processed by a com-
panion microcontroller such as the MAXQ3108. One
channel operates at a fixed 1x gain, while the other
operates at a pin-selectable gain of 1x, 4x, 16x, or 32x.
The DS8102 includes an internal power-supply monitor,
on-board voltage reference, and low-power oscillator to
reduce the number of external components required for
data acquisition.
The Manchester-encoded output from the DS8102
combines pulse-density-modulated measurement val-
ues from both differential input channels with a syn-
chronization bit stream and is transmitted over a single
pin. This transmission scheme is ideal for split voltage
domain applications where the DS8102 and other “hot”-
side components must be electrically isolated from
“cold” low-voltage components such as a companion
microcontroller. In this type of application, the DS8102
can be capacitively coupled to a companion microcon-
troller with only two connection points required
(MNOUT and DGND).
The MAXQ3108 dual-core microcontroller, which
includes specialized Manchester bit-stream decoding
inputs and sinc3 filters, is specifically designed to act
as a companion microcontroller for up to three DS8102
devices. This configuration, which supports up to six
differential analog input channels, is well suited for
three-phase electricity-metering applications.
Features
♦
Dual Delta-Sigma 2nd-Order Modulators
Channel 0: Pin-Selectable Gain of 1x, 4x, 16x,
or 32x
Channel 1: Fixed Gain of 1x
♦
Selectable Internal or External Voltage Reference
♦
Manchester-Encoded Bit Stream Output
Includes Synchronization Bits to Allow Clock
Recovery
Single-Pin Transmission Scheme Simplifies
Electrical Isolation Using Capacitive Coupling
♦
Selectable Internal or External Clock Source
♦
Integrated Low-Power 8MHz Oscillator
♦
Operating Mode
Active Mode (8MHz, V
DD
= 3.6V): 3.5mA
DS8102
Ordering Information
PART
DS8102+
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 TSSOP
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Pin Configuration
TOP VIEW
DGND
AGND
V
REF
AN1-
AN1+
AN0-
AN0+
V
DD
1
2
3
4
5
6
7
8
DS8102
+
Applications
Single-Phase Electricity Metering
Three-Phase Electricity Metering
Power-Line Conditioning
Electrochemical and Optical Sensors
Industrial Control
Data-Acquisition Systems and Data Loggers
16
15
14
13
12
11
10
9
V
DD
APDREF
RST
MNOUT
CLKIO
G1
G0
CLKSEL
TSSOP
Typical Operating Circuit appears at end of data sheet.
MAXQ is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Dual Delta-Sigma Modulator and Encoder
DS8102
ABSOLUTE MAXIMUM RATINGS
Voltage Range on V
DD
Relative to DGND.............-0.3V to +4.0V
Voltage Range on V
DD
Relative to AGND .............-0.3V to +4.0V
Voltage Range on AGND Relative to DGND .........-0.3V to +0.3V
Voltage Range on Any Pin Relative to DGND
Except AN0+, AN0-, and AN1+, AN1- ...............-0.3V to +4.0V
Voltage Range on AN0+, AN0-, AN1+, and AN1-
Relative to AGND ...............................................-4.0V to +4.0V
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Soldering Temperature...........................Refer to the IPC/JEDEC
J-STD-020 Specification.
Stresses beyond those listed under “Absolute Maximum Ratings” 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 the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
DD
= 2.7V to 3.6V, T
A
= -40°C to +85°C, f
CLK
= 8MHz, V
REF
= internal, OSR = 128, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage
Power-Fail Reset Voltage
Active V
DD
Current
Shutdown (Power-Down) V
DD
Current
Input Low Voltage
Input High Voltage
Output Low Voltage
(CLKIO, MNOUT)
Output High Voltage
(CLKIO, MNOUT)
Input/Output Pin Capacitance
Input Leakage Current (All Inputs)
CLOCK SOURCE
External Clock Input Frequency
External Clock Input Period
External Clock Input Duty Cycle
Internal Oscillator Output
Frequency
SYMBOL
V
DD
V
RST
I
DD
I
STOP
V
IL
V
IH
V
OL
V
OH
C
IO
I
L
f
XCLK
CLKSEL = 1
I
OL
= 4mA
I
OH
= -4mA
(Note 3)
-100
DC
125
40
7.5
47.8
8.0
49.1
60
8.5
49.7
Monitors V
DD
Normal operation
RST = 0 or V
DD
< V
RST
DGND
0.7 x V
DD
DGND
V
DD
- 0.4
15
+100
8
CONDITIONS
MIN
V
RST
2.7
TYP
(Note 2)
3.3
2.8
3.5
2
0.3 x V
DD
V
DD
0.4
MAX
3.6
2.99
5.0
UNITS
V
V
mA
nA
V
V
V
V
pF
nA
MHz
ns
%
MHz
%
t
XCLK-CLCL
CLKSEL = 1
t
XCLK-DUTY
CLKSEL = 1
f
ICLK
CLKSEL = 0
CLKSEL = 0
Internal Oscillator Output Duty
t
ICLK-DUTY
Cycle
ANALOG-TO-DIGITAL CONVERTER
AFE Warmup Delay
Reference Buffer Warmup Delay
t
WU1
t
WU2
f
ICLK
= 8MHz (Notes 1, 4)
f
ICLK
= 8MHz (Notes 1, 5)
OSR = 32
16
19
22
24
±0.01
OSR = 64
OSR = 128
OSR = 256
1.02
7.17
ms
ms
Decimator Output (Note 6)
Bits
Integral Nonlinearity
Offset Error
INL
(Notes 1, 6)
Gain = 1 (Note 6)
%FSR
1.4
mV
2
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Dual Delta-Sigma Modulator and Encoder
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 2.7V to 3.6V, T
A
= -40°C to +85°C, f
CLK
= 8MHz, V
REF
= internal, OSR = 128, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
(Note 2)
MAX
UNITS
DS8102
ANALOG-TO-DIGITAL CONVERTER DYNAMIC SPECIFICATIONS
DC Power-Supply Rejection Ratio
PSRR
V
DD
= 3.0V to 3.6V, AN0+ = AN0- = AGND,
100mV ripple on V
DD
V
DD
= 3.6V, gain = 1, AN0 = 500mV
P-P
,
sinewave at 62.5Hz
V
DD
= 3.6V, gain = 32, AN0 = 20mV
P-P
,
sinewave at 62.5Hz
V
DD
= 3.6V, gain = 32, AN0 = 20mV
P-P
,
sinewave at 62.5Hz
AN0+, AN0-, AN1+, and AN1- to AGND
Gain = 1
Input Sampling Capacitance
(Note 1)
Input Sampling Rate
Input Impedance to AGND for
8MHz (Note 8)
C
IN
Gain = 4
Gain = 16
Gain = 32
f
S
Clock at 8MHz (Note 7)
Gain = 1
Gain = 4
Gain = 16
Gain = 32
Gain = 1
Differential Input Impedance for
8MHz (Note 9)
Input Bandwidth (-3dB)
External Reference Input Voltage
External Reference Input
Sampling Capacitance
Reference Input Sampling Rate
INTERNAL REFERENCE
Reference Output Voltage
1.24
V
Reference Output Temperature
±30
ppm/°C
Coefficient
Note 1:
Specifications to -40°C are guaranteed by design and not production tested.
Note 2:
Typical values are not guaranteed. These values are measured at room temperature, V
DD
= 3.3V.
Note 3:
These numbers are guaranteed by design and are not tested.
Note 4:
Calculated as t
WU1
= 1/f
ICLK
x 8192.
Note 5:
Calculated as t
WU2
= 1/f
ICLK
x 57,344.
Note 6:
Parameter specifications are based upon the presence of an external cubic sinc filter (as implemented in the MAXQ3108)
for generating full ADC output codewords.
Note 7:
f
S
= f
CLK
/12. f
CLK
is the system clock frequency.
Note 8:
This is a function of input sampling capacitance (C
IN
) and sampling frequency, and can be approximated as 6/(f
CLK
x C
IN
).
Note 9:
Z
IN
(differential) = 2 x Z
IN
(single-ended).
f
S
V
REF
1.2
Gain = 4
Gain = 16
Gain = 32
-1
1
4
16
32
0.667
750
187
47
23.4
1500
375
94
46.9
7
1.25
2
0.67
1
1.3
kHz
V
pF
MHz
k
k
MHz
pF
70
70
95
85
dB
85
-95
-70
dB
dB
Signal-to-Noise Ratio
SINAD
Total Harmonic Distortion
THD
(to 21st Harmonic)
ANALOG-TO-DIGITAL CONVERTER INPUTS
Input Voltage Range
+1
V
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3
Dual Delta-Sigma Modulator and Encoder
DS8102
Pin Description
PIN
1
2
3
4
5
6
7
8, 16
9
NAME
DGND
AGND
V
REF
AN1-
AN1+
AN0-
AN0+
V
DD
CLKSEL
Digital Ground
Analog Ground
Reference Voltage Input/Output. When APDREF = 0, the buffered internal voltage reference is driven on
this pin as an output and can be used by other devices. When APDREF = 1, an external voltage
reference must be provided on this pin.
Negative Input for Differential Analog Input Channel 1
Positive Input for Differential Analog Input Channel 1
Negative Input for Differential Analog Input Channel 0
Positive Input for Differential Analog Input Channel 0
Digital and Analog Power Supply
Clock Select Input. When CLKSEL = 0, the DS8102 uses its internal 8MHz oscillator as a clock source.
When CLKSEL = 1, the DS8102 operates from an external clock source (which must be provided at
CLKIO).
Gain Select Input 0. This pin, along with G1, is used to select the gain setting for differential analog
input channel 0.
Gain Select Input 1. This pin, along with G0, is used to select the gain setting for differential analog
input channel 0.
Clock Input/Output. When CLKSEL = 0 (internal clock selected), the internal 8MHz clock is output on
this pin and can be used by external devices. When CLKSEL = 1 (external clock selected), an external
clock must be provided on this pin.
Manchester Encoder Output. This output pin provides a Manchester-encoded bit stream containing
output bits from both modulators interleaved with an alternating synchronization bit.
Reset. This input pin can be used to force the DS8102 into a shutdown (low-power) state by driving
RST = 0. If the external reset function is not used, this pin must be connected to V
DD
for proper
operation. An RC circuit is not required on this pin for power-up, as this function is provided internally.
Analog Power-Down Reference. This input pin controls whether the internal voltage reference is
enabled. If APDREF = 0, the internal voltage reference is enabled and the voltage reference level is
driven out on V
REF
. If APDREF = 1, the internal voltage reference is disabled and an external voltage
reference must be provided on V
REF
.
FUNCTION
10
11
G0
G1
12
CLKIO
13
MNOUT
14
RST
15
APDREF
4
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Dual Delta-Sigma Modulator and Encoder
Functional Diagram
APDREF
RST
DS8102
INTERNAL
REFERENCE
V
REF
REFERENCE
BUFFER
8MHz
OSCILLATOR
CLKSEL
CLKIO
AN1+
AN1-
1x
INTEGRATORS/
COMPARATOR
DS8102
DELTA-SIGMA MODULATOR
1x, 4x,
16x, 32x
MANCHESTER
ENCODER
MNOUT
AN0+
AN0-
INTEGRATORS/
COMPARATOR
POWER
MONITOR
DELTA-SIGMA MODULATOR
G1
G0
AGND
DGND
V
DD
Detailed Description
Operating Modes
The DS8102 has two operating modes: shutdown (or
power-down) mode and active mode.
1) Drive the RST line on the DS8102 low to force the
DS8102 into shutdown mode.
2) Enter stop mode. Both the companion microcon-
troller and the DS8102 are now in their lowest cur-
rent consumption modes.
3) Exit stop mode.
4) Drive the RST line on the DS8102 high to return the
DS8102 to active mode.
Note: The RST line on the DS8102 does not include
a pullup. This means that if the RST line is not dri-
ven by a companion microcontroller, RST must be
connected to V
DD
for proper operation. RST cannot
be left unconnected.
While the DS8102 is in shutdown mode, the levels on
the configuration input pins (APDREF, CLKSEL, G1,
and G0) can be changed if they are being driven by a
companion microcontroller instead of hardwired to V
DD
or DGND. However, once the DS8102 enters active
mode, the levels on these pins must remain static for
proper operation.
Shutdown Mode
In shutdown mode, the DS8102 is in an inactive state
and consumes a minimal amount of current. No analog-
to-digital conversion or encoding is performed, and the
internal 8MHz oscillator and internal voltage reference
are disabled.
An integrated power-supply monitor holds the DS8102
in shutdown mode whenever V
DD
≤
V
RST
. Additionally,
the RST pin can be driven low by an external compan-
ion microcontroller (such as the MAXQ3108) to force the
DS8102 to remain in shutdown mode, regardless of the
supply level at V
DD
. This is useful in nonisolated config-
urations (when a power supply is shared between the
DS8102 and the companion microcontroller) to reduce
the current consumption of the entire system. In this
scenario, the companion microcontroller would perform
this sequence of actions when entering stop mode:
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