2002 Microchip Technology Inc.
DS21409B-page 1
TC3400
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
260
µ
A; Sleep: 0.75
µ
A
• microPort™ Serial Bus Requires only two
Interface Lines
• Uses Internal or External Reference
• Automatically Enters Sleep Mode when not in use
Applications
• Consumer Electronics, Thermostats, CO
Monitors, Humidity Meters, Security Sensors
• Embedded Systems, Data Loggers, Portable
Equipment
• Medical Instruments
Device Selection Table
Package Type
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.
Part Number
Package
Temperature
Range
TC3400VPA
8-Pin PDIP (Narrow)
0
°
C to +85
°
C
TC3400VOA
8-Pin SOIC (Narrow)
0
°
C to +85
°
C
IN-
REF
IN
IN+
1
2
3
4
8
7
6
5
TC3400
8-Pin SOIC
8-Pin PDIP
GND
SDAT
SCLK
REF
OUT
V
DD
IN-
REF
IN
IN+
1
2
3
4
8
7
6
5
TC3400
GND
SDAT
SCLK
REF
OUT
V
DD
+1.8V, Low Power, 16-Bit Sigma-Delta A/D Converter
TC3400
DS21409B-page 2
2002 Microchip Technology Inc.
Typical Application
Functional Block Diagram
TC3400
µ
Controller
SDAT
SCLK
REF
OUT
REF
IN
IN1+
IN1-
I/01
I/02
V
BATT
C1
0.1
µF
R3
390
V
DD
V
CC
+
IN+
IN-
SDAT
REF
IN
REF
OUT
SCLK
Clock Generator
and Control
Circuitry
Data
Shift
Reg.
S – D
Modulator
+
–
x2
CONV Done
CONVCLK
1.193V
TC3400
V
DD
CLK
OUT
GND
2002 Microchip Technology Inc.
DS21409B-page 3
TC3400
1.0
ELECTRICAL
CHARACTERISTICS
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
*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.
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
Parameter
Min
Typ
Max
Unit
Test Conditions
Power Supply
V
DD
Supply Voltage
1.8
—
5.5
V
I
DD
Supply Current, During Data Conversion
—
260
—
µ
A
I
DD
SLEEP
Supply Current, Sleep Mode
—
0.75
1.5
µ
A
T
A
= +25°C
—
1.2
3.0
µ
A
Accuracy (Differential Inputs)
RES
Resolution
—
16
—
Bits
INL
Integral Non-Linearity
—
.0038
—
%FSR
V
DD
= 2.7V
V
OS
Offset Error
—
—
±0.9
%FSR
IN+, IN- = 0V
V
NOISE
Referred to input
—
60
—
µ
Vrms
CMR
Common Mode Rejection
—
75
—
dB
At DC
FSE
Full Scale Error
—
0.4%
—
%FS
PSRR
Power Supply Rejection Ratio
—
75
—
dB
V
DD
= 2.5V to 3.5V
IN+, IN-
V
IN
±
Differential Input Voltage
—
—
2.5
V
Note 1
Absolute Voltage Range on IN+, IN-
—
—
V
DD
V
Input Bias Current
—
1
100
nA
C
IN
Input Sampling Capacitance
—
2
—
pF
R
IN
Differential Input Resistance
—
2.0
—
M
Ω
Note 2
REF
IN,
REF
OUT
V
REF
REF
IN
Voltage Range
0
—
1.25
V
I
REF
REF
IN
Input Current
—
1
—
µA
V
REF
OUT
REF
OUT
Voltage
—
1.193
—
V
REF
SINK
REF
OUT
Current Sink Capability
—
10
—
µ
A
REF
SRC
REF
OUT
Current Source Capability
300
—
—
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
DS21409B-page 4
2002 Microchip Technology Inc.
TC3400 AC ELECTRICAL SPECIFICATIONS
SCLK
V
IL
Input Low Voltage
—
—
0.3 x V
DD
V
V
IH
Input High Voltage
0.7 x V
DD
—
—
V
I
LEAK
Leakage Current
—
1
—
µ
A
SDAT
V
OL
Output Low Voltage
—
—
0.4
V
I
OL
= 1.5mA
V
OH
Output High Voltage (SDAT)
0.9 x V
DD
—
—
V
I
SOURCE
= 400
µ
A (Note 3)
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
Parameter
Min
Typ
Max
Unit
Test Conditions
t
1
Resolution Reduction Clock Width
1
—
—
µsec
Width of SCLK (Negative)
t
2
Resolution Reduction Clock Width
1
—
—
µsec
Width of SCLK (Positive)
t
3
Conversion Time (15-bit Plus Sign)
—
125
—
msec
16-bit Conversion, T
A
= 25°C (Note 1)
Conversion Time (14-bit Plus Sign)
—
t
3
/2.0
—
msec
15-bit Conversion
Conversion Time (13-bit Plus Sign)
—
t
3
/4.0
—
msec
14-bit Conversion
Conversion Time (12-bit Plus Sign)
—
t
3
/7.8
—
msec
13-bit Conversion
Conversion Time (11-bit Plus Sign)
—
t
3
/15.1
—
msec
12-bit Conversion
Conversion Time (10-bit Plus Sign)
—
t
3
/28.6
—
msec
11-bit Conversion
Conversion Time (9-bit Plus Sign)
—
t
3
/51.4
—
msec
10-bit Conversion
t
4
Resolution Reduction Window
—
t
3
/85.7
—
msec
Width of SCLK
t
5
SCLK to Data Valid
1000
—
—
nsec
SCLK Falling Edge to SDAT Valid
t
8
Acknowledge Delay
—
—
1000
nsec
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
.
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
Parameter
Min
Typ
Max
Unit
Test Conditions
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 5
TC3400
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
Pin No.
(8-Pin SOIC)
(8-Pin PDIP)
Symbol
Description
1
IN+
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.
2
IN-
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.
3
REF
IN
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
.
4
GND
Ground Terminal.
5
REF
OUT
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.
6
SDAT
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).
7
SCLK
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.
8
V
DD
Power Supply Input.
TC3400
DS21409B-page 6
2002 Microchip Technology Inc.
3.0
DETAILED DESCRIPTION
The TC3400 is a 16-bit sigma-delta A/D converter with
one differential input. See the Typical Application circuit
and the Functional Block diagram. The key components
of the TC3400 are described below.
Also refer to Figure 3-4, A/D Operational Flowchart and
the Timing Diagrams, Figure 3-1, Figure 3-2 and
Figure 3-3).
3.1
A/D Converter Operation
When the TC3400 is not converting, it is in sleep mode
with both the SCLK and SDAT lines high. An A/D
conversion is initiated by a high to low transition on the
SCLK line at which time the internal clock of the
TC3400 is started. Each additional high to low
transition of SCLK (following the initial SCLK falling
edge) during the time interval t
4
, will decrement the
conversion resolution by one bit and reduce the
conversion time by one half. The time interval t
4
is
referred to as the resolution reduction window. The
minimum conversion resolution is 10-bits so any more
than 6 SCLK transitions during t
4
will be ignored.
After each high to low transition of SCLK, in the t
4
interval, the SDAT output is driven high by the TC3400
to acknowledge that the conversion has been decre-
mented. When the SCLK returns high or the t
4
interval
ends, the SDAT line returns low (see Figure 3-2). When
the conversion is complete SDAT is driven high. The
TC3400 now enters sleep mode and the conversion
value can be read as a serial data word on the SDAT
line.
3.2
Reading the Data Word
After the conversion is complete and SDAT goes high,
the conversion value can be clocked serially onto the
SDAT line by high to low transitions of the SCLK. The
data word is in two’s compliment format with the sign bit
clocked onto the SDAT line, first followed by the MSB
and ending in the LSB. For a 16-bit conversion the data
word would consist of a sign bit followed by 15 magni-
tude bits, Table 3-1 shows the data word versus input
voltage for a 16-bit conversion. Note that the full scale
input voltage range is ±(2 REF
IN
– 1LSB). When
REF
OUT
is fed back directly to REF
IN
, an LSB is 73
µ
V
for a 16-bit conversion, as REF
OUT
is typically 1.193V.
Figure 3-3 shows typical SCLK and SDAT waveforms
for 16, 12 and 10-bit conversions. Note that any
complete convert and read cycle requires 17 negative
edge clock pulses. The first is the convert command.
Then, up to six of these can occur in the resolution
reduction window, t
4
, to decrement resolution. The
remaining pulses clock out the conversion data word.
TABLE 3-1:
DATA CONVERSION WORD
VS. VOLTAGE INPUT
(REF
IN
= 1.193V)
The SCLK input has a filter which rejects any positive
or negative pulse of width less than 50nsec to reduce
noise. The rejection width of this pulse can vary
between 50nsec and 750nsec depending on process-
ing parameters and supply voltage.
Figure 3-1 and Table 3-2 show information for deter-
mining the mode of operation for the TC3400 part by
recording the value of SDAT for SCLK in a high, then
low, then high state. For example, if SCLK goes
through a 1-0-1 transition and the corresponding val-
ues of SDAT are 1-1-0, then the SCLK falling edge
started a new data conversion. A 0-1-0 for SDAT would
have indicated a resolution reduction had occurred.
This is useful if the microcontroller has a watchdog
reset or otherwise loses track of where the TC3400 is
in the conversion and data readout sequence. The
microcontroller can simply transition SCLK until it
“finds” a Start Conversion condition.
FIGURE 3-1:
SCLK, SDAT LOGIC
STATE DIAGRAM
TABLE 3-2:
SCLK, SDAT LOGIC STATE
*
Note: The code X00 has a dual meaning: Data Transfer or
Busy converting. To avoid confusion, the user should
send only the required number of pulses for the
desired resolution, then wait for SDAT to rise to 1,
indicating conversion is complete before clocking
SCLK again to read out data bits.
Data Word
INn+ – INn- (Volts)
0111 1111 1111 1111
2.38596 (Positive Full Scale)
0000 0000 0000 0001
72.8 E -6
0000 0000 0000 0000
0
1111 1111 1111 1111
-72.8 E -6
1000 0000 0000 0001
-2.38596 (Negative Full Scale)
1000 0000 0000 0000
Reserved Code
A
B
C
Status
1
1
0
Start Conversion
0
1
0
Resolution Reduction
x
1
1
Data Transfer
x
0
0
Data Transfer or Busy*
SCLK
SDAT
A
B
C
2002 Microchip Technology Inc.
DS21409B-page 7
TC3400
FIGURE 3-2:
CONVERSION AND DATA OUTPUT TIMING
FIGURE 3-3:
SCLK AND SDAT WAVEFORMS FOR 16, 12 AND 10-BIT CONVERSIONS
SCLK
SDAT
t
4
t
1
t
2
t
3
t
8
t
8
D
N-1
D
N-2
D
0
(LSB)
D
N
(MSB)
t
5
Data Conversion
Complete
Start Conversion and Resolution Control Timing
Data Output Timing
Sleep
Mode
SCLK
SDAT
t
3
a
16-bit Data Conversion,
Data Word A5A5h
SCLK
SDAT
16-bit Data Conversion, Long Start Pulse,
Data Word 5A5Ah
> t
3
a
Data Conversion
Complete
SCLK
SDAT
12-bit Conversion,
Data Word = AB3h
SCLK
SDAT
t
3
g
10-bit Conversion with "Extra"
Data Reduction Clocks, Data Word = 3A4h
Data Conversion
Complete
Data Conversion
Complete
Data Conversion
Complete
t
3
e
< t
4
< t
4
TC3400
DS21409B-page 8
2002 Microchip Technology Inc.
FIGURE 3-4:
A/D OPERATIONAL FLOWCHART
Yes
No
Yes
No
Yes
Yes
Yes
No
No
No
Yes
Yes
No
Yes
No
POR
Sleep
SDAT = High
SCLK
Hgh to Low?
Power Up Analog,
Start CONVCLK (= 0),
Start Conversion,
Resolution = 2m
(m = 16), Latch Input
Channel Address (if applicable).
SCLK
Low to High
transition?
SDAT = Low
CONVCLK
< 2
9
?
SCLK
High to Low?
A/D
Resolution
> 2
10
?
Reduce A/D
Resolution by 1-bit
(m = m – 1);
SDAT = High
SDAT = Low
CONVCLK = 2m?
(Conversion Done?)
Power Down Analog,
Conversion Complete,
SDAT = High
SCLK
High to Low?
SDAT = Dm;
m = m – 1
m
≥ 0?
SDAT = High
Internal Reset
Sleep
No
2002 Microchip Technology Inc.
DS21409B-page 9
TC3400
4.0
PACKAGING INFORMATION
4.1
Package Marking Information
Package marking data not available at this time.
4.2
Taping Forms
Component Taping Orientation for 8-Pin SOIC (Narrow) Devices
Package
Carrier Width (W)
Pitch (P)
Part Per Full Reel
Reel Size
8-Pin SOIC (N)
12 mm
8 mm
2500
13 in
Carrier Tape, Number of Components Per Reel and Reel Size
Standard Reel Component Orientation
for TR Suffix Device
PIN 1
User Direction of Feed
P
W
TC3400
DS21409B-page 10
2002 Microchip Technology Inc.
4.3
Package Dimensions
3
° MIN.
PIN 1
.260 (6.60)
.240 (6.10)
.045 (1.14)
.030 (0.76)
.070 (1.78)
.040 (1.02)
.400 (10.16)
.348 (8.84)
.200 (5.08)
.140 (3.56)
.150 (3.81)
.115 (2.92)
.110 (2.79)
.090 (2.29)
.022 (0.56)
.015 (0.38)
.040 (1.02)
.020 (0.51)
.015 (0.38)
.008 (0.20)
.310 (7.87)
.290 (7.37)
.400 (10.16)
.310 (7.87)
8-Pin Plastic DIP
Dimensions: inches (mm)
.050 (1.27) TYP.
8
°
MAX.
PIN 1
.244 (6.20)
.228 (5.79)
.157 (3.99)
.150 (3.81)
.197 (5.00)
.189 (4.80)
.020 (0.51)
.013 (0.33)
.010 (0.25)
.004 (0.10)
.069 (1.75)
.053 (1.35)
.010 (0.25)
.007 (0.18)
.050 (1.27)
.016 (0.40)
8-Pin SOIC
Dimensions: inches (mm)