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A0A1NC
40 39 3841
21
NC
22 23 24
CS
37
36
35
34
33
32
31
30
29
28
27
26
25
WR
OE
DGND
DGND
CLK
DV
DD
DV
DD
D0
D1
D2
DV
DD
DGND
NC – No internal connection
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
D10
DGND
D9D8D7
DD
D11
DV
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
DD
DV
D5D4D3
D6
Copyright 1999, Texas Instruments Incorporated
1
THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
description
The THS1401, THS1403, and THS1408 are 14-bit, 1/3/8 MSPS, single supply analog-to-digital converters with
an internal reference, differential inputs, programmable input gain, and an on-chip sample and hold amplifier .
Implemented with a CMOS process, the device has outstanding price/performance and power/speed ratios.
The THS1401, THS1403, and THS1408 are designed for use with 3.3-V systems, and with a high-speed µP
compatible parallel interface, making them the first choice for solutions based on high-performance DSPs like
the TI TMS320C6000 series.
The THS1401, THS1403, and THS1408 are available in a TQFP-48 package in standard commercial and
industrial temperature ranges.
CLK32IClock input
CML4Reference midpoint. This pin requires a 0.1-µF capacitor to AGND.
CS37IChip select input. Active low
DGND9, 15, 25,
DV
DD
D[13:0]11, 12, 13,
NC38, 39No connection, do not use. Reserved
IN+48IPositive differential analog input
IN–1INegative dif ferential analog input
OE35IOutput enable. Active low
OV10OOut of range output
REF+5OPositive reference output. This pin requires a 0.1-µF capacitor to AGND.
REF–6ONegative reference output. This pin requires a 0.1-µF capacitor to AGND.
VBG3IReference input. This pin requires a 1-µF capacitor to AGND.
WR36IWrite signal. Active low
45, 46
2, 43, 47PAnalog power supply
33, 34
14, 20, 26,
30, 31, 42
16, 17, 18,
19,21, 22,
23, 24, 27,
28, 29
PAnalog ground
PDigital ground
PDigital power supply
I/OData inputs/outputs
SLAS248 – DECEMBER 1999
absolute maximum ratings over operating free-air temperature (unless otherwise noted)
Lead temperature 1.6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
†
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 under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
3
THS1401, THS1403, THS1408
Operating free-air temperature
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
recommended operating conditions
PARAMETERMINNOMMAXUNIT
Supply voltage, AVDD, DV
High level digital input, V
Low level digital input, V
Load capacitance, C
Clock frequency, f
Clock duty cycle40%50%60%
p
CLK
DD
IH
IL
L
THS14010.111MHz
THS14030.133MHz
THS14080.188MHz
p
C suffix02570°C
I suffix–402585°C
electrical characteristics over recommended operating conditions
PARAMETERTEST CONDITIONSMINTYPMAXUNIT
Power Supply
I
DDA
I
DDD
DC Characteristics
DNLDifferential nonlinearity±0.6±1LSB
INLIntegral nonlinearity
AC Characteristics
ENOBEffective number of bits11.21 1.5Bits
THDTotal harmonic distortion
SNRSignal-to-noise ratio
SINADSignal-to-noise ratio + distortion
SFDRSpurious free dynamic range
Analog supply current8190mA
Digital supply current510mA
Power270360mW
Power down current20µA
Positive analog input, IN+0AV
Negative analog input, IN–0AV
Analog input voltage difference∆Ain = IN+ – IN–, V
Input impedance25kΩ
PGA range07dB
PGA step size1dB
PGA gain error±0.25dB
Digital Inputs
V
IH
V
IL
Digital Outputs
V
OH
V
OL
I
OZ
Clock Timing (CS low)
f
CLK
t
d
High-level digital input2V
Low-level digital input0.8V
Input capacitance5pF
Input current±1µA
High-level digital outputIOH = 50 µA2.6V
Low-level digital outputIOL = 50 µA0.4V
Output current, high impedance±10µA
Clock frequency
Output delay time25ns
Latency9.5Cycles
THS1401, THS1403, THS1408
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
ref
V
V
V
DD
DD
= REF+ – REF––V
ref
THS14010.111MHz
THS1403
THS14080.188MHz
ref
0.133MHz
V
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
5
THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
PARAMETER MEASUREMENT INFORMATION
sample timing
The THS1401/3/8 core is based on a pipeline architecture with a latency of 9.5 samples. The conversion results
appear on the digital output 9.5 clock cycles after the input signal was sampled.
Analog
Input
S9
S11
S10
S12
CLK
Data
Out
t
w(CLK)
t
t
w(CLK)
d
C1C2
C3
Figure 1. Sample Timing
The parallel interface of the THS1401/3/8 ADC features 3-state buffers making it possible to directly connect
it to a data bus. The output buffers are enabled by driving the OE input low.
Besides the sample results, it is also possible to read back the values of the control register, the PGA register,
and the control register. Which register is read is determined by the address inputs A[1,0]. The ADC results are
available at address 0.
The timing of the control signals is described in the following sections.
THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
PRINCIPLES OF OPERATION
registers
The device contains several registers. The A register is selected by the values of bits A1 and A0:
A1A0Register
00Conversion result
01PGA
10Offset
11Control
T ables 1 and 2 describe how to read the conversion results and how to configure the data converter . The default
values (were applicable) show the state after a power-on reset.
Table 1. Conversion Result Register, Address 0, Read
BITD13D12D11D10D9D8D7D6D5D4D3D2D1D0
FunctionMSB...……………………………LSB
The output can be configured for two’s complement or straight binary format (see D11/control register).
The output code is given by:
PWD:Power down0 = normal operation1 = power down
REF:Reference select0 = internal reference1 = external reference
FOR:Output format0 = straight binary1 = 2s complement
TM2–0:Test mode000 = normal operation
001 = both inputs = REF–
010 = IN+ at V
011 = IN+ at REF+, IN– at REF–
100 = normal operation
101 = both inputs = REF+
110 = IN+ at REF–, IN– at V
111 = IN+ at REF–, IN– at REF+
OF:Offset correction0 = enable1 = disable
RESReservedMust be set to 0.
/2, IN– at REF–
ref
ref
/2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
15
THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
APPLICATION INFORMATION
driving the analog input
The THS1401/3/8 ADCs have a fully differential input. A differential input is advantageous with respect to SNR,
SFDR, and THD performance because the signal peak-to-peak level is 50% of a comparable single-ended
input.
There are three basic input configurations:
D
Fully differential
D
Transformer coupled single-ended to differential
D
Single-ended
fully differential configuration
In this configuration, the ADC converts the difference (∆IN) of the two input signals on IN+ and IN–.
22 Ω
100 pF
22 Ω
100 pF
IN+
THS1401/3/8
IN–
Figure 19. Differential Input
The resistors and capacitors on the inputs decouple the driving source output from the ADC input and also serve
as first order low pass filters to attenuate out of band noise.
The input range on both inputs is 0 V to A VDD. The full-scale value is determined by the voltage reference. The
positive full-scale output is reached, if ∆IN equals ∆REF , the negative full-scale output is reached, if ∆IN equals
–∆REF.
transformer coupled single-ended to differential configuration
If the application requires the best SNR, SFDR, and THD performance, the input should be transformer coupled.
The signal amplitude on both inputs of the ADC is one half as high as in a single-ended configuration thus
increasing the ADC ac performance.
22 Ω
100 pF
R
22 Ω
100 pF
+
1 µF0.1 µF
Figure 20. Transformer Coupled
IN+
THS1401/3/8
IN–
CML
IN [V
–∆REF– full scale
†
n = 1 (winding ratio)
]OUTPUT [
PEAK
00
∆REF+ full scale
PEAK
]
†
†
The resistor R of the transformer coupled input configuration must be set to match the signal source impedance
R = n2 Rs, where Rs is the source impedance and n is the transformer winding ratio.
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
17
THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
APPLICATION INFORMATION
single-ended configuration
In this configuration, the input signal is level shifted by ∆REF/2.
10 kΩ + 10 kΩ
REF+
10 kΩ10 kΩ
–
+
100 pF
22 Ω
100 pF
IN+
THS1401/3/8
IN–
REF–
10 kΩ
10 kΩ
Figure 21. Single-Ended With Level Shift
The following table shows the input voltages for negative full-scale output, zero output, and positive full-scale
output:
∆IN+ [V]OUTPUT
–∆REF– full scale
00
∆REF+ full scale
Note that the resistors of the op-amp and the op-amp all introduce gain and offset errors. Those errors can be
trimmed by varying the values of the resistors.
Because of the added offset, the op-amp does not necessarily operate in the best region of its transfer curve
(best linearity around zero) and therefore may introduce unacceptable distortion. For ac signals, an alternative
is described in the following section.
If the application does not require the signal bandwidth to include dc, the level shift shown in Figure 4 is not
necessary.
10 kΩ
10 kΩ
REF+
10 kΩ10 kΩ
–
+
100 pF
10 nF
22 Ω
100 pF
Figure 22. Single-Ended With Level Shift
IN+
THS1401/3/8
IN–
10 kΩ
10 kΩ
REF–
Because the signal swing on the op-amp is centered around ground, it is more likely that the signal stays within
the linear region of the op-amp transfer function, thus increasing the overall ac performance.
IN [V
–∆REF– full scale
]OUTPUT [
PEAK
00
∆REF+ full scale
PEAK
]
Compared to the transformer-coupled configuration, the swing on IN– is twice as big, which can decrease the
ac performance (SNR, SFD, and THD).
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
19
THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
APPLICATION INFORMATION
internal/external reference operation
The THS1401/3/8 ADC can either be operated using the built-in band gap reference or using an external
precision reference in case very high dc accuracy is needed.
The REF+ and REF+ outputs are given by:
2
ǒ
Ǔ
1
)
REF
)+
VBG
If the built-in reference is used, VBG equals 1.5 V which results in REF+ = 2.5 V, REF– = 0.5 V and ∆REF =
2V.
The internal reference can be disabled by writing 1 to D12 (REF) in the control register (address 3). The band
gap reference is then disconnected and can be substituted by a voltage on the VBG pin.
and REF–+VBGǒ1–
3
2
Ǔ
3
programmable gain amplifier
The on-chip programmable gain amplifier (PGA) has eight gain settings. The gain can be changed by writing
to the PGA gain register (address 1). The range is 0 to 7dB in steps of one dB.
out of range indication
The OV output of the ADC indicates an out of range condition. Every time the difference on the analog inputs
exceeds the differential reference, this signal is asserted. This signal is updated the same way as the digital data
outputs and therefore subject to the same pipeline delay.
offset compensation
With the offset register it is possible to automatically compensate system offset errors, including errors caused
by additional signal conditioning circuitry . If the offset compensation is enabled (D7 (OFF) in the control register),
the value in the offset register (address 2) is automatically subtracted from the output of the ADC.
In order to set the correct value of the offset compensation register , the ADC result when the input signal is 0
must be read by the host processor and written to the offset register (address 2).
test modes
The ADC core operation can be tested by selecting one of the available test modes (see control register
description). The test modes apply various voltages to the differential input depending on the setting in the
control register.
digital I/O
The digital inputs and outputs of the THS1401/3/8 ADC are 3-V CMOS compatible. In order to avoid current
feed back errors, the capacitive load on the digital outputs should be as low as possible (50 pF max). Series
resistors (100 Ω) on the digital outputs can improve the performance by limiting the current during output
transitions.
The parallel interface of the THS1401/3/8 ADC features 3-state buffers, making it possible to directly connect
it to a data bus. The output buffers are enabled by driving the OE
Refer to the read and write timing diagrams in the parameter measurement information section for information
on read and write access.
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-026
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
0,08
4073176/B 10/96
21
IMPORTANT NOTICE
T exas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue
any product or service without notice, and advise customers to obtain the latest version of relevant information
to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty . Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOL VE POTENTIAL RISKS OF
DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL
APPLICATIONS”). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR
WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER
CRITICAL APPLICA TIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERST OOD TO
BE FULLY AT THE CUSTOMER’S RISK.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
semiconductor products or services might be or are used. TI’s publication of information regarding any third
party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.
Copyright 1999, Texas Instruments Incorporated
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