Appendix A - Specifications [U3 Datasheet]

Parameter

Conditions

Min

Typical

Max

Units

General

USB Cable Length

5

meters

Supply Voltage

4

5

5.25

volts

Supply Current (1)

Hardware V1.21+

50

mA

Operating Temperature

-40

85

°C

Clock Error

-40 to 85 °C

1.5

%

Typ. Command Execution Time (2)

USB high-high

0.6

ms

USB other

4

ms

VS Outputs

Typical Voltage (3)

Self-Powered

4.75

5

5.25

volts

Bus-Powered

4

5

5.25

Maximum Currrent (3)

Self-Powered

450

mA

Bus-Powered

50

mA

(1) Typical current drawn by the U3 itself, not including any user connections.     

(2) Total typical time to execute a single Feedback function with no analog inputs. Measured by timing a Windows application that performs 1000 calls to the Feedback function. See Section 3.1 for more timing information.     

(3) These specifications are related to the power provided by the host/hub. Self- and bus-powered describes the host/hub, not the U3. Self-powered would apply to USB hubs with a power supply, all known desktop computer USB hosts, and some notebook computer USB hosts. An example of bus-powered would be a hub with no power supply, or many PDA ports. The current rating is the maximum current that should be sources through the U3 and out of the Vs terminals.     

Parameter

Conditions

Min

Typical

Max

Units

Analog Inputs

Typical input Range (4)

Single-Ended, LV

0

2.44

volts

Differential, LV

-2.44

2.44

volts

Special, LV

0

3.6

volts

Single-Ended, HV

-10.3

10.3

volts

Special, HV

-10.3

20.1

volts

Max AIN Voltage versus GND (5)

Valid Readings, LV

-0.3

3.6

volts

Valid Readings, HV

-12.8

20.1

volts

Max AIN Voltage versus GND (6)

No Damage, FIO

-10

10

volts

No Damage, EIO

-6

6

volts

No Damage, HV

-40

40

volts

Input Impedance (7)

LV

40

MΩ

HV

1.3

MΩ

Source Impedance (7)

Long Settling Off, LV

10

kΩ

Long Settling On, LV

200

kΩ

Long Settling Off, HV

1

kΩ

Long Settling On, HV

1

kΩ

Resolution

All Ranges

12

bits

Single-Ended, LV, 0-2.44

0.6

mV

Differential, LV, ±2.44

1.2

mV

Special, LV, 0-3.6

1.2

mV

Single-Ended, HV, ±10

5.0

mV

Special, HV, -10 to +20

10.0

mV

Integral Linearity Error

±0.05

% FS

Differential Linearity Error

±1

counts

Absolute Accuracy (8)

Single-Ended %

±0.13

% FS

Single-Ended LV volts

±3.2

mV

Single-Ended HV volts

±26.8

mV

Differential %

±0.25

% FS

Differential LV volts

±6.4

mV

Differential HV volts

N/A

Special 0-3.6 %

±0.25

% FS

Special LV volts

±6.4

mV

Special HV volts

±53.6

mV

Temperature Drift

15

ppm/°C

Noise (Peak-To-Peak) (9)

Quick Sample Off

±1

counts

Quick Sample On

±2

counts

Effective Resolution (RMS) (10)

Quick Sample Off

>12

bits

Noise-Free Resolution (9)

Quick Sample Off

11

bits

Command/Response Speed

See Section 3.1

Stream Performance

See Section 3.2

* LV specs refer to low voltage analog inputs which are available on the U3-LV and U3-HV.  HV specs refer to high voltage analog inputs which are available on the U3-HV only.

(4) Note that these are typical input ranges.  The actual minimum on the low voltage inputs might not go all the way to 0.0 as discussed in

.  These are with DAC1 disabled on hardware version < 1.30.

(5) This is the maximum voltage on any AIN pin compared to ground for valid measurements. Note that a differential channel has a minimum voltage of -2.44 volts, meaning that the positive channel can be 2.44 volts less than the negative channel, but no low-voltage AIN pin can go more than 0.3 volts below ground.     

(6) Maximum voltage, compared to ground, to avoid damage to the device. Protection level is the same whether the device is powered or not.     

(7) The low-voltage analog inputs essentially connect directly to a SAR ADC on the U3, presenting a capacitive load to the signal source. The high-voltage inputs connect first to a resistive level-shifter/divider. The key specification in both cases is the maximum source impedance. As long as the source impedance is not over this value, there will be no substantial errors due to impedance problems.     

(8) Absolute error includes INL, DNL, and all other sources of internal error at 25 C and VS=5.0V. To equate the percentage to voltage, multiply the full voltage span by the percentage.  For a single-ended low voltage input using the normal range the span is about 2.4 volts, so 2.4 * 0.0013 gives ±0.003 volts. For a single-ended high voltage input using the normal range the span is about 20 volts, so 20 * 0.0013 gives ±0.026 volts. Differential readings are not calibrated on high voltage channels.

(9) Measurements taken with AIN connected to a 2.048 reference (REF191 from Analog Devices) or GND. All "counts" data are aligned as 12-bit values. Noise-free data is determined by taking 128 readings and subtracting the minimum value from the maximum value.     

(10) Effective (RMS) data is determined from the standard deviation of 128 readings. In other words, this data represents most readings, whereas noise-free data represents all readings.     

Parameter

Conditions

Min

Typical

Max

Units

Analog Outputs (DAC)

Nominal Output Range (11)

No Load

0.04

4.95

volts

@ ±2.5 mA

0.225

4.775

volts

Resolution

10

bits

Absolute Accuracy

5% to 95% FS

±5

% FS

Integral Linearity Error

±1

counts

Differential Linearity Error

±1

counts

Max Output Current (12)

@ 2.0V

30

mA

Error Due To Loading (12)

@ 100 µA

0.1

%

@ 1 mA

1

%

Source Impedance (12)

50

Ω

Short Circuit Current (12,13)

5V to GND

50

mA

Cutoff Frequency (14)

-3 dB

16

Hz

Time Constant (14)

10

ms

Digital I/O, Timers, Counters

Low Level Input Voltage

-0.3

0.8

volts

Hight Level Input Voltage

2

5.8

volts

Maximum Input Voltage (15)

FIO

-10

10

volts

EIO/CIO

-6

6

volts

Output Low Voltage (16)

No Load

0

volts

--- FIO

Sinking 1 mA

0.55

volts

--- EIO/CIO

Sinking 1 mA

0.18

volts

--- EIO/CIO

Sinking 5 mA

0.9

volts

Output High Voltage (16)

No Load

3.3

volts

--- FIO

Sourcing 1 mA

2.75

volts

--- EIO/CIO

Sourcing 1 mA

3.12

volts

--- EIO/CIO

Sourcing 5 mA

2.4

volts

Short Circuit Current (16)

FIO

6

mA

EIO/CIO

18

mA

Input Impedance

Pull-up to 3.3V

100

kΩ

Series Impedance (16)

FIO

550

Ω

EIO/CIO

180

Ω

Counter Input Frequency (17)

Hardware V1.21+

8

MHz

Input Timer Total Edge Rate (18)

No Stream, V1.21+

30000

edges/s

While Streaming

7000

edges/s

(11) Maximum and minimum analog output voltage is limited by the supply voltages (Vs and GND). The specifications assume Vs is 5.0 volts. Also, the ability of the DAC output buffer to driver voltages close to the power rails, decreases with increasing output current, but in most applications the output is not sinking/sourcing much current as the output voltage approaches GND.     

(12) If the output is set to 3.5 volts and sourcing 30 mA, there will be about 2.0 volts at the DAC pin due to the 50 ohms of series impedance. Each DAC output is driven by a channel on an AD8544 op-amp, powered by VS & GND, and then goes through protection circuitry that includes 50 ohms of series impedance. The max output current is determined by 3 main factors: short circuit current, ability of AD8544 to sink/source near power rails (Figure 22 of

), and the 50 ohms of series impedance.

(13) Continuous short circuit will not cause damage.     

(14) The DAC outputs are creating by filtering PWM signals, and the 2nd order 16 Hz output filter works great for the default PWM frequency of 732 Hz, but with lower frequency timer clocks the DAC outputs will be noisier.  See Section 2.7 for more details.  Time constant is the time it take for the output to settle 63% of the way towards a new value.

(15) Maximum voltage to avoid damage to the device. Protection works whether the device is powered or not, but continuous voltages over 5.8 volts or less than -0.3 volts are not recommended when the U3 is unpowered, as the voltage will attempt to supply operating power to the U3 possible causing poor start-up behavior.     

(16) These specifications provide the answer to the question: "How much current can the digital I/O sink or source?". For instance, if EIO0 is configured as output-high and shorted to ground, the current sourced by EIO0 into ground will be about 18 mA (3.3/180). If connected to a load that draws 5 mA, EIO0 can provide that current but the voltage will droop to about 2.4 volts instead of the nominal 3.3 volts. If connected to a 180 ohm load to ground, the resulting voltage and current will be about 1.65 volts @ 9 mA.     

(17) Hardware counters. 0 to 3.3 volt square wave. Limit 2 MHz with older hardware versions.     

(18) To avoid missing edges, keep the total number of applicable edges on all applicable timers below this limit. See Section 2.9 for more information. Limit 10000 with older hardware versions.