TC3400
+1.8V, Low Power, 16-Bit Sigma-Delta A/D Converter
Features
• 16-bit Resolution at Eight Conversions Per
Second, Adjustable Down to 10-bit Resolution at
512 Conversions Per Second
• 1.8V – 5.5V Operation, Low Power Operating
260µA; Sleep: 0.75µA
• microPort™ Serial Bus Requires only two
Interface Lines
• Uses Internal or External Reference
• Automatically Enters Sleep Mode when not in use
Package Type
8-Pin SOIC
IN+
IN-
REF
IN
GND
1
2
3
4
8 V
DD
TC3400
7
6
5
SCLK
SDAT
REF
OUT
Applications
• Consumer Electronics, Thermostats, CO
Monitors, Humidity Meters, Security Sensors
• Embedded Systems, Data Loggers, Portable
Equipment
• Medical Instruments
IN+
IN-
REF
IN
GND
1
2
3
4
8-Pin PDIP
8 V
DD
TC3400
7
6
5
SCLK
SDAT
REF
OUT
Device Selection Table
Part Number
TC3400VPA
TC3400VOA
Package
8-Pin PDIP (Narrow)
8-Pin SOIC (Narrow)
Temperature
Range
0°C to +85°C
0°C to +85°C
General Description
The TC3400 is a low cost, low power analog-to-digital
converter based on Microchip’s Sigma-Delta technol-
ogy. It will perform 16-bit conversions (15-bit plus sign)
at up to eight per second. The TC3400 is optimized for
use as a microcontroller peripheral in low cost, battery
operated systems. A voltage reference is included, or
an external reference can be used.
The TC3400’s 2-wire microPort™ digital interface is
used for starting conversions and for reading out the
data. Driving the SCLK line low starts a conversion.
After the conversion starts, each additional falling edge
(up to six) detected on SCLK for t
4
seconds reduces
the A/D resolution by one bit and cuts conversion time
in half. After a conversion is completed, clocking the
SCLK line puts the MSB through LSB of the resulting
data word onto the SDAT line, much like a shift register.
The part automatically sleeps when not performing a
data conversion.
The TC3400 is available in a 8-Pin PDIP and a 8-Pin
SOIC package.
2002 Microchip Technology Inc.
DS21409B-page 1
©
TC3400
Typical Application
V
BATT
+
V
IN1+
IN1-
DD
V
CC
SDAT
SCLK
I/01
I/02
µ
Controller
TC3400
REF
IN
REF
OUT
C1
0.1µF
R3
390
Functional Block Diagram
V
DD
REF
OUT
TC3400
1.193V
x2
REF
IN
IN+
IN-
+
–
CONV Done
S–D
Modulator
Data
Shift
Reg.
SDAT
CONVCLK
Clock Generator
and Control
Circuitry
CLKOUT
SCLK
GND
©
DS21409B-page 2
2002 Microchip Technology Inc.
TC3400
1.0
ELECTRICAL
CHARACTERISTICS
*Stresses above 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 above those indicated in the
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability.
Absolute Maximum Ratings*
Supply Voltage ..................................................... 6.0V
Input Voltage (All Other Pins):
............................... (GND – 0.3V) to (V
DD
+ 0.3V)
Operating Temperature Range ................. 0°C to 85°C
Storage Temperature ........................ -65°C to +150°C
TC3400 DC ELECTRICAL SPECIFICATIONS
Electrical Characteristics:
T
A
= 25°C and V
DD
= 2.7V, unless otherwise specified.
Boldface
type specifications apply for
temperatures of 0°C to 85°C. V
REF
= 1.25V, Internal Clock Frequency = 520kHz.
Symbol
Power Supply
V
DD
I
DD
I
DD
SLEEP
Supply Voltage
Supply Current, During Data Conversion
Supply Current, Sleep Mode
1.8
—
—
—
Accuracy (Differential Inputs)
RES
INL
V
OS
V
NOISE
CMR
FSE
PSRR
IN+, IN-
V
IN
±
Differential Input Voltage
Absolute Voltage Range on IN+, IN-
Input Bias Current
C
IN
R
IN
Input Sampling Capacitance
Differential Input Resistance
—
—
—
—
—
—
—
1
2
2.0
2.5
V
DD
100
—
—
V
V
nA
pF
MΩ
Note 2
Note 1
Resolution
Integral Non-Linearity
Offset Error
Referred to input
Common Mode Rejection
Full Scale Error
Power Supply Rejection Ratio
—
—
—
—
—
—
—
16
.0038
—
60
75
0.4%
75
—
—
±0.9
—
—
—
—
Bits
%FSR
%FSR
V
DD
= 2.7V
IN+, IN- = 0V
At DC
V
DD
= 2.5V to 3.5V
—
260
0.75
1.2
5.5
—
1.5
3.0
V
Parameter
Min
Typ
Max
Unit
Test Conditions
µ
A
µ
A
µ
A
T
A
= +25°C
µ
Vrms
dB
%FS
dB
REF
IN,
REF
OUT
V
REF
I
REF
V
REF
OUT
REF
SINK
REF
SRC
REF
IN
Voltage Range
REF
IN
Input Current
REF
OUT
Voltage
REF
OUT
Current Sink Capability
REF
OUT
Current Source Capability
0
—
—
—
300
—
1
1.193
10
—
1.25
—
—
—
—
V
µA
V
µA
µ
A
Note 1:
Differential input voltage defined as (V
IN
+ – V
IN
-).
2:
Resistance from INn+ to INn- or INn to GND.
3:
@ V
DD
= 1.8V, I
SOURCE
≤
200
µ
A.
2002 Microchip Technology Inc.
DS21409B-page 3
©
TC3400
TC3400 DC ELECTRICAL SPECIFICATIONS (CONTINUED)
Electrical Characteristics:
T
A
= 25°C and V
DD
= 2.7V, unless otherwise specified.
Boldface
type specifications apply for
temperatures of 0°C to 85°C. V
REF
= 1.25V, Internal Clock Frequency = 520kHz.
Symbol
SCLK
V
IL
V
IH
I
LEAK
SDAT
V
OL
V
OH
Output Low Voltage
Output High Voltage (SDAT)
—
0.9 x V
DD
—
—
0.4
—
V
V
I
OL
= 1.5mA
I
SOURCE
= 400µA
(Note 3)
Input Low Voltage
Input High Voltage
Leakage Current
—
0.7 x V
DD
—
—
—
1
0.3 x V
DD
—
—
V
V
Parameter
Min
Typ
Max
Unit
Test Conditions
µ
A
Note 1:
Differential input voltage defined as (V
IN
+ – V
IN
-).
2:
Resistance from INn+ to INn- or INn to GND.
3:
@ V
DD
= 1.8V, I
SOURCE
≤
200
µ
A.
TC3400 AC ELECTRICAL SPECIFICATIONS
Electrical Characteristics:
T
A
= 25°C and V
DD
= 2.7V, unless otherwise specified.
Boldface
type specifications apply for
temperatures of 0°C to 85°C. V
REF
= 1.25V, Internal Clock Frequency = 520kHz.
Symbol
t
1
t
2
t
3
Parameter
Resolution Reduction Clock Width
Resolution Reduction Clock Width
Conversion Time (15-bit Plus Sign)
Conversion Time (14-bit Plus Sign)
Conversion Time (13-bit Plus Sign)
Conversion Time (12-bit Plus Sign)
Conversion Time (11-bit Plus Sign)
Conversion Time (10-bit Plus Sign)
Conversion Time (9-bit Plus Sign)
t
4
t
5
t
8
Resolution Reduction Window
SCLK to Data Valid
Acknowledge Delay
Min
1
1
—
—
—
—
—
—
—
—
1000
—
Typ
—
—
125
t
3
/2.0
t
3
/4.0
t
3
/7.8
t
3
/15.1
t
3
/28.6
t
3
/51.4
t
3
/85.7
—
—
Max
—
—
—
—
—
—
—
—
—
—
—
1000
Unit
µsec
µsec
msec
msec
msec
msec
msec
msec
msec
msec
nsec
nsec
Test Conditions
Width of SCLK (Negative)
Width of SCLK (Positive)
16-bit Conversion, T
A
= 25°C
(Note 1)
15-bit Conversion
14-bit Conversion
13-bit Conversion
12-bit Conversion
11-bit Conversion
10-bit Conversion
Width of SCLK
SCLK Falling Edge to SDAT Valid
SCLK to SDAT Delay
Note 1:
Nominal temperature drift is -2830ppm/C° for temperature less than 25°C and -1340ppm/°C for temperatures
greater than 25°C
.
©
DS21409B-page 4
2002 Microchip Technology Inc.
TC3400
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
Pin No.
(8-Pin SOIC)
(8-Pin PDIP)
1
2
3
PIN FUNCTION TABLE
Symbol
IN+
IN-
REF
IN
Description
Analog Input. This is the positive terminal of a true differential input consisting of IN+ and IN-.
V
IN1
= (IN+ – IN-). See Section 1.0 Electrical Characteristics.
Analog Input. This is the negative terminal of a true differential input consisting of IN+ and IN-.
V
IN
= (IN+ – IN-) IN- can swing to, but not below, ground.
Analog Input. The converter’s reference voltage is the differential between this pin and ground times
two. It may be tied directly to REF
OUT
or scaled using a resistor divider. Any user supplied reference
voltage less than 1.25V may be used in place of REF
OUT
.
Ground Terminal.
Analog Output. The internal reference connects to this pin. It may be scaled externally, if desired, and
tied to the REF
IN
input to provide the converter’s reference voltage. Care must be taken in connecting
external circuitry to this pin.
Digital Output (push-pull). This is the microPort™ serial data output. SDAT is driven low while the
TC3400 is converting data, effectively providing a “busy” signal. After the conversion is complete,
every high to low transition on the SCLK pin puts a bit from the resulting data word on the SDAT pin
(from MSB to LSB).
Digital Input. This is the microPort™ serial clock input. The TC3400 comes out of sleep mode and a
conversion cycle begins when this pin is driven low. After the conversion starts, each additional falling
edge (up to six) detected on SCLK for t
4
seconds reduces the A/D resolution by one bit. When the
conversion is complete, the data word can be shifted out on the SDAT pin by clocking the SCLK pin.
Power Supply Input.
4
5
GND
REF
OUT
6
SDAT
7
SCLK
8
V
DD
2002 Microchip Technology Inc.
DS21409B-page 5
©
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