Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLinear IC - Op-amp Programmable gain TSOT 23 8

LTC6910-1

LTC6910-2/LTC6910-3

6910123fa

, LTC and LT are registered trademarks of Linear Technology Corporation.

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3-Bit Digital Gain Control in Three Gain-Code

Options

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Rail-to-Rail Input Range

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Rail-to-Rail Output Swing

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Single or Dual Supply: 2.7V to 10.5V Total

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11MHz Gain Bandwidth Product

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Input Noise Down to 8nV/√Hz

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System Dynamic Range to 120dB

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Input Offset Voltage: 1.5mV

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8-Pin Low Profile (1mm) SOT-23

(ThinSOT™) Package

Digitally Controlled

Programmable

Gain Amplifiers in SOT-23

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Data Acquisition Systems

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Dynamic Gain Changing

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Automatic Ranging Circuits

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Automatic Gain Control

The LTC

6910 family are low noise digitally program-

mable gain amplifiers (PGAs) that are easy to use and

occupy very little PC board space. The inverting gain is

adjustable using a 3-bit digital input to select gains of 0, 1,

2, 5, 10, 20, 50 and 100V/V in the LTC6910-1; 0, 1, 2, 4,

8, 16, 32 and 64V/V in the LTC6910-2; and 0, 1, 2, 3, 4, 5,6

and 7V/V in the LTC6910-3.

The LTC6910-Xs are inverting amplifiers with rail-to-rail

output. When operated with unity gain, they will also

process rail-to-rail input signals. A half-supply reference

generated internally at the AGND pin supports single

power supply applications. Operating from single or split

supplies from 2.7V to 10.5V, the LTC6910-X family is

offered in an 8-lead SOT-23 package.

Single Supply Programmable Amplifier Frequency Response (LTC6910-1)

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

OUT

= GAIN • V

AGND

1µF OR LARGER

PIN 2 (AGND) PROVIDES BUILT-IN HALF-SUPPLY

REFERENCE WITH INTERNAL RESISTANCE OF 5k.

AGND CAN ALSO BE DRIVEN BY A SYSTEM ANALOG

GROUND REFERENCE NEAR HALF SUPPLY

6910 TA01

LTC6910-X

2.7V TO 10.5V

0.1µF

G2 G1 G0

6910-1

–1

–2

–5

–10

–20

–50

–100

6910-2

–1

–2

–4

–8

–16

–32

–64

GAIN IN VOLTS/VOLT

6910-3

–1

–2

–3

–4

–5

–6

–7

DIGITAL INPUTS

FREQUENCY (Hz)

GAIN (dB)

100 10k 100k 1M 10M

6910 TA01b

–10

GAIN OF 100 (DIGITAL INPUT 111)

GAIN OF 1 (DIGITAL INPUT 001)

GAIN OF 2 (DIGITAL INPUT 010)

GAIN OF 5 (DIGITAL INPUT 011)

GAIN OF 10 (DIGITAL INPUT 100)

GAIN OF 20 (DIGITAL INPUT 101)

GAIN OF 50 (DIGITAL INPUT 110)

= 10V, V

= 5mV

RMS

ThinSOT is a trademark of Linear Technology Corporation.

U.S. Patent Number 6121908.

Summary of content (24 pages)

PAGE 1
LTC6910-1 LTC6910-2/LTC6910-3 Digitally Controlled Programmable Gain Amplifiers in SOT-23 U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®6910 family are low noise digitally programmable gain amplifiers (PGAs) that are easy to use and occupy very little PC board space. The inverting gain is adjustable using a 3-bit digital input to select gains of 0, 1, 2, 5, 10, 20, 50 and 100V/V in the LTC6910-1; 0, 1, 2, 4, 8, 16, 32 and 64V/V in the LTC6910-2; and 0, 1, 2, 3, 4, 5,6 and 7V/V in the LTC6910-3.
PAGE 2
LTC6910-1 LTC6910-2/LTC6910-3 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) Total Supply Voltage (V+ to V–) ............................. 11V Input Current ..................................................... ±25mA Operating Temperature Range (Note 2) LTC6910-1C, -2C, -3C ........................ – 40°C to 85°C LTC6910-1I, -2I, -3I ........................... – 40°C to 85°C LTC6910-1H, -2H, -3H ....................
PAGE 3
LTC6910-1 LTC6910-2/LTC6910-3 U U U GAI SETTI GS A D PROPERTIES Table 2. LTC6910-2 G2 0 0 0 0 1 1 1 1 G1 0 0 1 1 0 0 1 1 G0 0 1 0 1 0 1 0 1 NOMINAL VOLTAGE GAIN Volts/Volt (dB) 0 –120 –1 0 –2 6 –4 12 –8 18.1 –16 24.1 –32 30.1 –64 36.1 NOMINAL LINEAR INPUT RANGE (VP-P) Dual 5V Single 5V Single 3V Supply Supply Supply 10 5 3 10 5 3 5 2.5 1.5 2.5 1.25 0.75 1.25 0.625 0.375 0.625 0.313 0.188 0.313 0.156 0.094 0.156 0.078 0.047 NOMINAL INPUT IMPEDANCE (kΩ) (Open) 10 5 2.5 1.25 1.25 1.25 1.
PAGE 4
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted. PARAMETER CONDITIONS C, I SUFFIXES MIN TYP MAX MIN 2.7 2.7 H SUFFIX TYP MAX UNIT Specifications for the LTC6910-1, LTC6910-2 and LTC6910-3 Total Supply Voltage 10.5 V Supply Current VS = 2.7V, VIN = 1.
PAGE 5
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted. PARAMETER LTC6910-1C/LTC6910-1I LTC6910-1H MIN TYP MAX MIN TYP MAX CONDITIONS UNIT Specifications for LTC6910-1 Only Voltage Gain (Note 7) VS = 2.7V, Gain = 1, RL = 10k VS = 2.
PAGE 6
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted.
PAGE 7
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted. PARAMETER LTC6910-2C/LTC6910-2I LTC6910-2H MIN TYP MAX MIN TYP MAX CONDITIONS UNIT Specifications for LTC6910-2 Only Voltage Gain (Note 7) VS = 2.7V, Gain = 1, RL = 10k VS = 2.7V, Gain = 1, RL = 500Ω ● ● – 0.
PAGE 8
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted.
PAGE 9
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted. PARAMETER LTC6910-3C/LTC6910-3I LTC6910-3H MIN TYP MAX MIN TYP MAX CONDITIONS UNIT Specifications for LTC6910-3 Only Voltage Gain (Note 7) VS = 2.7V, Gain = 1, RL = 10k VS = 2.7V, Gain = 1, RL = 500Ω ● ● – 0.
PAGE 10
LTC6910-1 LTC6910-2/LTC6910-3 ELECTRICAL CHARACTERISTICS The ● denotes the specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 5V, AGND = 2.5V, Gain = 1 (Digital Inputs 001), RL = 10k to midsupply point, unless otherwise noted. PARAMETER LTC6910-3C/LTC6910-3I LTC6910-3H MIN TYP MAX MIN TYP MAX CONDITIONS UNIT Specifications for LTC6910-3 Only 0.4 0.7 1 1.3 1.6 1.9 2.2 2.5 0.4 0.7 1 1.3 1.6 1.9 2.2 2.
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LTC6910-1 LTC6910-2/LTC6910-3 U W TYPICAL PERFOR A CE CHARACTERISTICS (LTC6910-1) LTC6910-1 Gain Shift vs Temperature 50 VS = ± 2.5V OUTPUT UNLOADED VS = ±5V, VIN = 5mVRMS GAIN OF 100 40 GAIN CHANGE (dB) GAIN = 100 30 GAIN (dB) GAIN = 10 0 GAIN = 1 –3dB FREQUENCY (MHz) GAIN OF 50 0.1 GAIN OF 20 GAIN OF 10 20 GAIN OF 5 10 GAIN OF 2 –0.1 GAIN OF 1 0 0 50 100 TEMPERATURE (°C) –10 100 150 1k 10k 100k FREQUENCY (Hz) 1M 10M LTC6910-1 Output Voltage Swing vs Load Current +VS – 1.
PAGE 12
LTC6910-1 LTC6910-2/LTC6910-3 U W TYPICAL PERFOR A CE CHARACTERISTICS (LTC6910-2) LTC6910-2 Gain Shift vs Temperature 0.2 LTC6910-2 –3dB Bandwidth vs Gain Setting LTC6910-2 Frequency Response 50 VS = ± 2.5V OUTPUT UNLOADED VS = ±5V VIN = 10mVRMS GAIN CHANGE (dB) GAIN (dB) GAIN = 8 0 GAIN OF 32 30 GAIN = 64 GAIN = 1 –3dB FREQUENCY (MHz) 40 GAIN OF 64 0.1 GAIN OF 16 20 GAIN OF 8 GAIN OF 4 10 GAIN OF 2 –0.
PAGE 13
LTC6910-1 LTC6910-2/LTC6910-3 U W TYPICAL PERFOR A CE CHARACTERISTICS (LTC6910-3) LTC6910-3 Gain Shift vs Temperature 0.02 LTC6910-3 –3dB Bandwidth vs Gain Setting LTC6910-3 Frequency Response 20 VS = ± 2.5V OUTPUT UNLOADED 8.0 GAIN OF 7 GAIN OF 6 15 GAIN = 4 GAIN OF 3 5 GAIN OF 2 GAIN OF 1 0 GAIN = 1 –0.01 –5 0 50 100 TEMPERATURE (°C) –10 100 150 1k +VS – 1.0 10k 100k FREQUENCY (Hz) 1M 90 80 –VS + 2.0 –VS + 1.5 –VS + 1.0 60 50 –SUPPLY 40 30 0.1 1 10 OUTPUT CURRENT (mA) 0 0.
PAGE 14
LTC6910-1 LTC6910-2/LTC6910-3 U U U PI FU CTIO S Recommended analog ground plane connection depends on how power is applied to the LTC6910-X (Figures 1, 2, and 3). Single power supply applications typically use V– for the system signal ground. The analog ground plane in single-supply applications should therefore tie to V–, and the AGND pin should be bypassed to this ground plane by a high quality capacitor of at least 1µF (Figure 1).
PAGE 15
LTC6910-1 LTC6910-2/LTC6910-3 U U U PI FU CTIO S Where AGND does not connect to a ground plane, as in Figures 1 and 3, it is important to AC-bypass the AGND pin. This is especially true when AGND is used as a reference voltage for other circuitry. Also, without a bypass capacitor, wideband noise will enter the signal path from the internal voltage divider resistors that set the DC voltage on AGND. This noise can reduce SNR by 3dB at high gain settings.
PAGE 16
LTC6910-1 LTC6910-2/LTC6910-3 U U U PI FU CTIO S V–, V+ (Pins 4, 8): Power Supply Pins. The V+ and V– pins should be bypassed with 0.1µF capacitors to an adequate analog ground plane using the shortest possible wiring. Electrically clean supplies and a low impedance ground are important for the high dynamic range available from the LTC6910-X (see further details under AGND). Low noise linear power supplies are recommended.
PAGE 17
LTC6910-1 LTC6910-2/LTC6910-3 U W U U APPLICATIO S I FOR ATIO Functional Description The LTC6910 family are small outline, wideband inverting DC amplifiers whose voltage gain is digitally programmable. Each delivers a choice of eight voltage gains, controlled by the 3-bit digital inputs to the G pins, which accept CMOS logic levels. The gain code is always monotonic; an increase in the 3-bit binary number (G2 G1 G0) causes an increase in the gain.
PAGE 18
LTC6910-1 LTC6910-2/LTC6910-3 U W U U APPLICATIO S I FOR ATIO Offset Nulling and Drift these internal 10k resistors also have an absolute tolerance of up to ±30% and a temperature coefficient of typically –30ppm/°C.) Also, as described under Pin Functions for AGND, a bypass capacitor C1 is always advisable when AGND is not connected directly to a ground plane.
PAGE 19
LTC6910-1 LTC6910-2/LTC6910-3 U W U U APPLICATIO S I FOR ATIO Analog Input and DC Levels As described in Tables 1, 2 and 3 and under Pin Functions, the IN pin presents a variable input resistance returned internally to a potential equal to that at the AGND pin (within a small offset-voltage error). This input resistance varies with digital gain setting, becoming infinite (open circuit) at “zero” gain (digital input 000), and as low as 1kΩ at high gain settings.
PAGE 20
LTC6910-1 LTC6910-2/LTC6910-3 U TYPICAL APPLICATIO S the LTC6910-3 (gains 0V to 7V/V) it is 117dB. The SNR from an amplifier is the ratio of input level to inputreferred noise, and can be 110dB with the LTC6910 family at unity gain. Construction and Instrumentation Cautions Electrically clean construction is important in applications seeking the full dynamic range of the LTC6910-X amplifier. Short, direct wiring will minimize parasitic capacitance and inductance. High quality supply bypass capacitors of 0.
PAGE 21
LTC6910-1 LTC6910-2/LTC6910-3 U TYPICAL APPLICATIO Figure 7 shows a block diagram and Figure 8 the practical circuit for a low noise amplifier with gain and bandwidth independently programmable over 100:1 ranges. One LTC6910-X controls the gain and another controls the bandwidth. An LT1884 dual op amp forms an integrating lowpass loop with capacitor C2 to set the programmable upper corner frequency. The LT1884 also supports rail-torail output swings over the total supply voltage range of 2.7V to 10.5V.
PAGE 22
LTC6910-1 LTC6910-2/LTC6910-3 U TYPICAL APPLICATIO S Measured frequency responses in Figure 8 with LTC6910-1 PGAs demonstrate bandwidth settings of 10Hz, 100Hz and 1kHz, with digital codes at the BW inputs of respectively 001, 100 and 111, and unity gain in each case. By scaling C2, this circuit can serve other bandwidths, such as a maximum of 10kHz with 0.1µF using LT1884 (gain-bandwidth product around 1MHz).
PAGE 23
LTC6910-1 LTC6910-2/LTC6910-3 U PACKAGE DESCRIPTIO TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.52 MAX 2.90 BSC (NOTE 4) 0.65 REF 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.22 – 0.36 8 PLCS (NOTE 3) 0.65 BSC 0.80 – 0.90 0.09 – 0.20 (NOTE 3) 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 24
LTC6910-1 LTC6910-2/LTC6910-3 U TYPICAL APPLICATIO AC-Coupled Single Supply Amplifiers V+ 2.7V TO 10.5V 0.