Table Of Contents

PCIe-6738 Specifications

    Last Modified: June 8, 2018


    Warranted specifications describe the performance of a model under stated operating conditions and are covered by the model warranty.

    Characteristics describe values that are relevant to the use of the model under stated operating conditions but are not covered by the model warranty.

    • Typical specifications describe the performance met by a majority of models.
    • Nominal specifications describe an attribute that is based on design, conformance testing, or supplemental testing.

    Specifications are Typical unless otherwise noted.


    Specifications are valid at 25 °C unless otherwise noted.

    Analog Output

    Number of channels

    32 voltage outputs


    16 bits, 1 in 65,536


    ±1.0 LSB maximum

    Unscaled data format[1]

    Unsigned integer (0 to 65,535)


    16 bits


    Refer to the AO Absolute Accuracy table

    Maximum update rate (using local FIFO)[2]

    1 channel

    1 MS/s

    8 channels (1 channel per bank)[3]

    1 MS/s

    32 channels[3]

    350 kS/s

    Timing accuracy (warranted)

    50 ppm of sample rate

    Timing resolution

    10 ns

    Output range

    ±10 V

    Output coupling


    Output impedance

    0.2 Ω

    Output current drive[4]

    ±10 mA

    Overdrive protection

    ±15 V

    Overdrive current

    15 mA

    Power-on state

    ±200 mV

    Power-on/off glitch

    3.0 V peak for 100 ms

    FIFO buffer size

    65,535 samples shared among channels used

    Data transfers

    DMA (scatter-gather), programmed I/O

    AO waveform modes
    • Nonperiodic waveform
    • Periodic waveform regeneration mode from onboard FIFO
    • Periodic waveform regeneration from host buffer including dynamic update

    Settling time, full scale step

    15 µs to ±4 LSB

    Slew rate

    3.0 V/µs


    1.0 mV RMS, DC to 1 MHz

    AO update glitch


    3.0 mV


    10 µs

    Glitch energy

    3 nVs

    Channel crosstalk

    -65 dB with SHC68-68-A2 cable (generating a 10 V, 100 point sinusoidal at 100 kHz on the reference channel)

    Output stability

    Any passive load


    AO update glitch is the glitch energy that occurs on all channels on the same bank as the result of a channel update, regardless of value. For example, if you update the value of AO 0, all channels within that bank AO <0..3> will experience this glitch regardless of whether their output voltages change.

    Absolute Accuracy (Warranted)

    Absolute accuracy at full-scale number is valid immediately following self calibration and assumes the device is operating within 10 °C of the last external calibration.
    Table 1. AO Absolute Accuracy
    Nominal Range Positive Full Scale Nominal Range Negative Full Scale Residual Gain Error (ppm of Reading) Gain Tempco (ppm/°C) Reference Tempco (ppm/°C) Offset Tempco (ppm) Residual Offset Error (ppm of Range) INL Error (ppm of Range) Absolute Accuracy at Full Scale (µV)
    10 -10 109 12 1 4 95 64 2,940

    Accuracies listed are valid for up to two years from the device external calibration.

    AO Absolute Accuracy Equation

    AbsoluteAccuracy = OutputValue · (GainError) + Range · (OffsetError)

    • GainError = ResidualGainError + GainTempco · (TempChangeFromLastInternalCal) + ReferenceTempco · (TempChangeFromLastExternalCal)
    • OffsetError = ResidualOffsetError + OffsetTempco · (TempChangeFromLastInternalCal) + INL_Error

    Electromagnetic interference can adversely affect the measurement accuracy of this product. The analog output pins of this device are not protected for lectromagnetic interference. As a result, this device may experience reduced accuracy or other temporary performance degradation when connected cables are routed in an environment with radiated or conducted radio frequency electromagnetic interference.

    Digital I/O/PFI

    Static Characteristics

    Number of channels

    10 total, 2 (P0.<0..1>), 8 (PFI<0..7>/P1.<0..7>)

    Ground reference

    D GND

    Direction control

    Each terminal individually programmable as input or output

    Pull-down resistor

    50 kΩ typical, 20 kΩ minimum

    Input voltage protection[5]

    ±20 V on up to two pins

    Waveform Characteristics (Port 0 Only)

    Terminals used

    Port 0 (P0.<0.1>)

    Port/sample size

    Up to 2 bits

    Waveform generation (DO) FIFO

    2,047 samples

    Waveform acquisition (DI) FIFO

    255 samples

    DI Sample Clock Frequency

    0 to 10 MHz, system and bus activity dependent

    DO Sample Clock frequency

    Regenerate from FIFO

    0 to 10 MHz

    Streaming from memory

    0 to 10 MHz, system and bus activity dependent

    Data transfers

    DMA (scatter-gather), programmed I/O

    Digital line filter settings

    160 ns, 10.24 µs, 5.12 ms, disable

    PFI/Port 1 Functionality


    Static digital input, static digital output, timing input, timing output

    Timing output sources

    Many AI, AO, counter, DI, DO timing signals

    Debounce filter settings

    90 ns, 5.12 µs, 2.56 ms, custom interval, disable; programmable high and low transitions; selectable per input

    Recommended Operating Conditions

    Input high voltage (VIH)

    2.2 V minimum, 5.25 V maximum

    Input low voltage (VIL)

    0 V minimum, 0.8 V maximum

    Output high current (IOH)


    -24 mA maximum

    PFI <0..7>/PI<0..7>

    -16 mA maximum

    Output low current (IOL)


    24 mA maximum

    PFI <0..7>/P1<0..7>

    16 mA maximum

    Electrical Characteristics

    Level Minimum Maximum
    Positive-going threshold (VT+)

    Negative-going threshold (VT-)

    0.8 V

    2.2 V

    Delta VT hysteresis (VT+ - VT-) 0.2 V
    IIL input low current (Vin = 0 V)

    IIH input high current (Vin = 5 V)

    -10 µA

    250 µA

    Digital I/O Characteristics

    Figure 1. P0.<0..1>: IOH versus VOH
    Figure 2. PFI <0..7>/PI: IOH versus VOH
    Figure 3. P0.<0..1>: IOL versus VOL
    Figure 4. PFI <0..7>/P1: IOL versus VOL

    Timing I/O

    Number of counter/timers



    32 bits

    Counter measurements

    Edge counting, pulse, pulse width, semi-period, period, two-edge separation

    Position measurements

    X1, X2, X4 quadrature encoding with Channel Z reloading; two-pulse encoding

    Output applications

    Pulse, pulse train with dynamic updates, frequency division, equivalent time sampling

    Internal base clocks

    100 MHz, 20 MHz, 100 kHz

    External base clock frequency

    0 MHz to 25 MHz

    Base clock accuracy (warranted)

    50 ppm


    Gate, Source, HW_Arm, Aux, A, B, Z, Up_Down, Sample Clock

    Routing options for inputs

    Any PFI, RTSI, analog trigger, many internal signals


    127 samples per counter

    Data transfers

    Dedicated scatter-gather DMA controller for each counter/timer, programmed I/O

    Phase-Locked Loop (PLL)

    Number of PLLs


    Table 2. Reference Clock Locking Frequencies
    Reference Signal Locking Input Frequency (MHz)
    RTSI <0..7> 10, 20
    PFI <0..7> 10, 20

    Outside of PLL

    100 MHz Timebase; other signals derived from 100 MHz Timebase including 20 MHz and 100 kHz Timebases

    External Digital Triggers


    Any PFI, RTSI


    Software-selectable for most signals

    Analog output function

    Start Trigger, Pause Trigger, Sample Clock, Sample Clock Timebase

    Counter/timer functions

    Gate, Source, HW_Arm, Aux, A, B, Z, Up_Down, Sample Clock

    Digital waveform generation (DO) function

    Start Trigger, Pause Trigger, Sample Clock, Sample Clock Timebase

    Digital waveform acquisition (DI) function

    Start Trigger, Reference Trigger, Pause Trigger, Sample Clock, Sample Clock Timebase

    Device-to-Device Trigger Bus

    Input source

    RTSI <0..7>

    Output destination

    RTSI <0..7>

    Output selections

    10 MHz Clock; many internal signals

    Debounce filter settings

    90 ns, 5.12 µs, 2.56 ms, custom interval, disable; programmable high and low transitions; selectable per input

    Bus Interface

    Form factor

    x4 PCI Express, specification v1.1 compliant

    Slot compatibility

    x4, x8, and x16 PCI Express slots[6]

    DMA channels

    7 DMA, analog output, digital input, digital output, counter/timer 0, counter/timer 1, counter/timer 2, counter/timer 3

    Power Requirements


    The protection provided by the PCIe-6738 can be impaired if it is used in a manner not described in the user documentation.

    +3.3 V

    3.0 W

    +12 V

    14.0 W

    Current Limits


    Exceeding the current limits may cause unpredictable behavior by the device and/or chassis.

    +5 V terminal (connector 0)

    1 A maximum[7]

    P0/P1/PFI terminals combined

    1.4 A maximum


    Printed circuit board dimensions

    16.8 cm × 11.1 cm (6.60 in. × 4.38 in.)


    110 g (3.8 oz)

    I/O connector

    1 68-pin VHDCI

    Form factor

    Standard height, half length, single slot

    Integrated air mover (fan)



    Recommended warm-up time

    15 minutes

    Calibration interval

    2 years

    Safety Voltages

    Connect only voltages that are below these limits.

    Channel-to-earth ground

    ±11 V, Measurement Category I

    Measurement Category I is for measurements performed on circuits not directly connected to the electrical distribution system referred to as MAINS voltage. MAINS is a hazardous live electrical supply system that powers equipment. This category is for measurements of voltages from specially protected secondary circuits. Such voltage measurements include signal levels, special equipment, limited-energy parts of equipment, circuits powered by regulated low-voltage sources, and electronics.


    Do not connect the PCIe-6738 to signals or use for measurements within Measurement Categories II, III, or IV.


    Measurement Categories CAT I and CAT O are equivalent. These test and measurement circuits are for other circuits not intended for direct connection to the MAINS building installations of Measurement Categories CAT II, CAT III, or CAT IV.


    Maximum altitude

    2,000 m (800 mbar) (at 25 °C ambient temperature)

    Pollution degree


    Indoor use only.


    Clean the device with a soft, non-metallic brush. Make sure that the device is completely dry and free from contaminants before returning it to service.

    This product meets the requirements of the following environmental standards for electrical equipment for measurement, control, and laboratory use.

    Operating Environment

    Operating temperature, local[8]

    0 °C to 55 °C

    (IEC 60068-2-1 and IEC 60068-2-2)

    Operating humidity

    10% to 90% RH, noncondensing

    (IEC 60068-2-78)

    System slot airflow

    0.4 m/s (80 LFM)

    Storage Environment

    Ambient temperature range

    -20 °C to 70 °C

    (IEC 60068-2-1 and IEC 60068-2-2)

    Relative humidity range

    5% to 95% RH, noncondensing

    (IEC 60068-2-78)

    Safety Compliance Standards

    This product is designed to meet the requirements of the following electrical equipment safety standards for measurement, control, and laboratory use:

    • IEC 61010-1, EN 61010-1
    • UL 61010-1, CSA C22.2 No. 61010-1

    For UL and other safety certifications, refer to the product label or the Product Certifications and Declarations section.

    Electromagnetic Compatibility Standards

    This product meets the requirements of the following EMC standards for electrical equipment for measurement, control, and laboratory use:

    • EN 61326-1 (IEC 61326-1): Class A emissions; Basic immunity
    • EN 55011 (CISPR 11): Group 1, Class A emissions
    • AS/NZS CISPR 11: Group 1, Class A emissions
    • FCC 47 CFR Part 15B: Class A emissions
    • ICES-001: Class A emissions

    Group 1 equipment (per CISPR 11) is any industrial, scientific, or medical equipment that does not intentionally generate radio frequency energy for the treatment of material or inspection/analysis purposes.


    In the United States (per FCC 47 CFR), Class A equipment is intended for use in commercial, light-industrial, and heavy-industrial locations. In Europe, Canada, Australia and New Zealand (per CISPR 11) Class A equipment is intended for use only in heavy-industrial locations.

    CE Compliance

    This product meets the essential requirements of applicable European Directives, as follows:

    • 2014/35/EU; Low-Voltage Directive (safety)
    • 2014/30/EU; Electromagnetic Compatibility Directive (EMC)
    • 2011/65/EU; Restriction of Hazardous Substances (RoHS)

    Product Certifications and Declarations

    Refer to the product Declaration of Conformity (DoC) for additional regulatory compliance information. To obtain product certifications and the DoC for NI products, visit, search by model number or product line, and click the appropriate link in the Certification column.

    Environmental Management

    NI is committed to designing and manufacturing products in an environmentally responsible manner. NI recognizes that eliminating certain hazardous substances from our products is beneficial to the environment and to NI customers.

    For additional environmental information, refer to the Minimize Our Environmental Impact web page at This page contains the environmental regulations and directives with which NI complies, as well as other environmental information not included in this document.

    Waste Electrical and Electronic Equipment (WEEE)

    EU Customers  

    At the end of the product life cycle, all NI products must be disposed of according to local laws and regulations. For more information about how to recycle NI products in your region, visit



    National Instruments符合中国电子信息产品中限制使用某些有害物质指令(RoHS)。关于National Instruments中国RoHS合规性信息,请登录。(For information about China RoHS compliance, go to

    • 1 Used for writing unscaled or raw data and covers the range from negative full scale (0) to positive full scale (65,535).
    • 2 These numbers apply to continuous waveform generation using onboard memory only, which allows for the highest update rate by doing a single transfer of data over the bus. The maximum update rate in FIFO mode does not change regardless of the number of devices in the system.
    • 3 All analog output channels are grouped into banks, as shown in your device pinout. Each bank consists of four AO channels using one DAC. Any channels being used within a single bank will update simultaneously.
    • 4 Analog output channels are designed for four-quadrant (source and sink) operation.
    • 5 Stresses beyond those listed under Input voltage protection may cause permanent damage to the device.
    • 6 Some motherboards reserve the x16 slot for graphics use. For PCI Express guidelines, visit and enter the Info Code PCIExpress.
    • 7 Has a self-resetting fuse that opens when current exceeds this specification.
    • 8 For PCI Express adapter cards with integrated air movers, NI defines the local operational ambient environment to be at the fan inlet. For cards without integrated air movers, NI defines the local operational ambient environment to be 25 mm (1 in.) upstream of the leading edge of the card. For more information about the local operational ambient environment definition for PCI Express adapter cards, visit and enter the Info Code pcielocalambient.

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