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LTC6244

6244fb

Dual 50MHz, Low Noise,

Rail-to-Rail, CMOS Op Amp

The LTC

6244 is a dual high speed, unity-gain stable CMOS

op amp that features a 50MHz gain bandwidth, 40V/µs slew

rate, 1pA of input bias current, low input capacitance and

rail-to-rail output swing. The 0.1Hz to 10Hz noise is just

1.5µV

P-P

and 1kHz noise is guaranteed to be less than

12nV/√Hz. This excellent AC and noise performance is

combined with wide supply range operation, a maximum

offset voltage of just 100µV and drift of only 2.5µV/°C,

making it suitable for use in many fast signal processing

applications, such as photodiode ampliﬁ ers.

This op amp has an output stage that swings within 35mV

of either supply rail to maximize the signal dynamic range

in low supply applications. The input common mode

range extends to the negative supply. It is fully speciﬁ ed

on 3V and 5V, and an HV version guarantees operation

on supplies of ±5V.

The LTC6244 is available in the 8-pin MSOP, and for com-

pact designs, it is packaged in the tiny dual ﬁ ne pitch lead

free (DFN) package.

Photodiode Ampliﬁ ers

Charge Coupled Ampliﬁ ers

Low Noise Signal Processing

Active Filters

Medical Instrumentation

High Impedance Transducer Ampliﬁ er

Input Bias Current: 1pA (Typ at 25°C)

Low Offset Voltage: 100μV Max

Low Offset Drift: 2.5μV/°C Max

0.1Hz to 10Hz Noise: 1.5µV

P-P

Slew Rate: 40V/µs

Gain Bandwidth Product: 50MHz

Output Swings Rail-to-Rail

Supply Operation:

2.8V to 6V LTC6244

2.8V to ±5.25V LTC6244HV

Low Input Capacitance: 2.1pF

Available in 8-Pin MSOP and Tiny DFN Packages

Very Low Noise Large Area Photodiode

Distribution

TYPICAL APPLICATION

DESCRIPTION

FEATURES

APPLICATIONS

OUT

= 1M • I

BW = 350kHz

NOISE = 291nV AT 10kHz

PHILIPS

BF862

JFET

HAMAMATSU LARGE AREA

PHOTODIODE

S1227-1010BQ

= 3000pF

* CAN BE MICROPHONIC, FILM, X7R, IF NEEDED.

0.25pF

–5V

6244 TA01a

–

1/2

LTC6244HV

–5V

4.99k

4.7µF*

4.99k

OUT

INPUT OFFSET VOLTAGE (µV)

–60 –40

NUMBER OF UNITS

100

120

6244 TA01b

110

–20

20 40

LTC6244MS8

= 5V, 0V

= 2.5V

= 25°C

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

Summary of content (26 pages)

PAGE 1
LTC6244 Dual 50MHz, Low Noise, Rail-to-Rail, CMOS Op Amp FEATURES DESCRIPTION n The LTC®6244 is a dual high speed, unity-gain stable CMOS op amp that features a 50MHz gain bandwidth, 40V/μs slew rate, 1pA of input bias current, low input capacitance and rail-to-rail output swing. The 0.1Hz to 10Hz noise is just 1.5μVP-P and 1kHz noise is guaranteed to be less than 12nV/√Hz.
PAGE 2
LTC6244 ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (V+ to V–) LTC6244..................................................................7V LTC6244HV ...........................................................12V Input Voltage.......................... (V+ + 0.3V) to (V– – 0.3V) Input Current........................................................±10mA Output Short Circuit Duration (Note 2)............. Indeﬁnite Operating Temperature Range LTC6244C ............................................
PAGE 3
LTC6244 ELECTRICAL CHARACTERISTICS (LTC6244C/I, LTC6244HVC/I) The l denotes the speciﬁcations which apply over the speciﬁed temperature range, otherwise speciﬁcations are at TA = 25°C. VS = 5V, 0V, VCM = 2.5V unless otherwise noted.
PAGE 4
LTC6244 ELECTRICAL CHARACTERISTICS (LTC6244C/I, LTC6244HVC/I) The l denotes the speciﬁcations which apply over the speciﬁed temperature range, otherwise speciﬁcations are at TA = 25°C. VS = 5V, 0V, VCM = 2.5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS GBW Gain Bandwidth Product Frequency = 100kHz, RL = 1kΩ l 35 50 MHz SR Slew Rate (Note 11) AV = –2, RL = 1kΩ l 18 35 V/μs FPBW Full Power Bandwidth (Note 12) VOUT = 3VP-P, RL = 1kΩ l 1.9 3.
PAGE 5
LTC6244 ELECTRICAL CHARACTERISTICS (LTC6244C/I, LTC6244HVC/I) The l denotes the speciﬁcations which apply over the speciﬁed temperature range, otherwise speciﬁcations are at TA = 25°C. VS = 3V, 0V, VCM = 1.5V unless otherwise noted. SYMBOL PARAMETER IS Supply Current per Ampliﬁer GBW Gain Bandwidth Product CONDITIONS MIN l Frequency = 100kHz, RL = 1kΩ l 35 TYP MAX 4.8 5.
PAGE 6
LTC6244 ELECTRICAL CHARACTERISTICS (LTC6244HVC/I) The l denotes the speciﬁcations which apply over the speciﬁed temperature range, otherwise speciﬁcations are at TA = 25°C. VS = ±5V, 0V, VCM = 0V unless otherwise noted. SYMBOL PSRR PARAMETER MIN TYP l 75 110 dB PSRR Match Channel-to-Channel (Note 5) l 73 106 dB 2.8 40 55 mA Power Supply Rejection CONDITIONS VS = 2.8V to 10.5V, VCM = 0.
PAGE 7
LTC6244 ELECTRICAL CHARACTERISTICS (LTC6244H) The l denotes the speciﬁcations which apply from –40°C to 125°C, otherwise speciﬁcations are at TA = 25°C. VS = 5V, 0V, VCM = 2.5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS TYP MAX UNITS 75 dB l 73 dB l 2.
PAGE 8
LTC6244 ELECTRICAL CHARACTERISTICS (LTC6244HVH) The l denotes the speciﬁcations which apply from –40°C to 125°C, otherwise speciﬁcations are at TA = 25°C. VS = ±5V, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage (Note 4) DD8 Package VOS Match Channel-to-Channel (Note 5) DD8 Package TC VOS Input Offset Voltage Drift, MS8 (Note 6) IB Input Bias Current (Notes 4, 7) IOS MIN l l l MAX UNITS 100 700 1050 μV μV 150 900 1165 μV μV 0.7 2.
PAGE 9
LTC6244 ELECTRICAL CHARACTERISTICS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: A heat sink may be required to keep the junction temperature below the absolute maximum rating when the output is shorted indeﬁnitely. Note 3: The LTC6244C/LTC6244HVC are guaranteed to meet speciﬁed performance from 0°C to 70°C.
PAGE 10
LTC6244 TYPICAL PERFORMANCE CHARACTERISTICS VOS Distribution 60 120 LTC6244MS8 VS = 5V, 0V VCM = 2.5V TA = 25°C 100 50 NUMBER OF UNITS NUMBER OF UNITS 90 LTC6244DD VS = 5V, 0V VCM = 2.
PAGE 11
LTC6244 TYPICAL PERFORMANCE CHARACTERISTICS Output Saturation Voltage vs Load Current (Output Low) 10 1 0.1 TA = 125°C TA = 25°C TA = –55°C 0.1 1 10 LOAD CURRENT (mA) VS = ±5V 1 0.1 TA = 125°C TA = 25°C TA = –55°C 0.01 0.1 100 1 10 LOAD CURRENT (mA) PHASE 60 60 40 20 GAIN 40 0 30 –20 20 –40 10 –60 0 –80 VS = ±5V VS = ±1.5V –10 –20 10k 100k 30 70 60 42 40 36 34 32 40 0 2 10 4 6 8 TOTAL SUPPLY VOLTAGE (V) 28 –50 12 AV = 1 0.01 100M 6244 G16 VS = ±5V VS = ±2.
PAGE 12
LTC6244 TYPICAL PERFORMANCE CHARACTERISTICS Power Supply Rejection Ratio vs Frequency NEGATIVE SUPPLY POSITIVE SUPPLY 60 50 40 30 20 10 0 200 150 100 50 0 –50 –100 –150 TA = 125°C TA = 25°C TA = –55°C –200 –250 –300 –10 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 0 1 2 3 4 5 6 7 8 TOTAL SUPPLY VOLTAGE (V) 6244 G19 –60 –70 RL = 10k –80 RL = 1k –90 –100 4 TA = 25°C VS = 5V, 0V –60 –70 RL = 10k –80 RL = 1k –90 –30 1.5 2 2.5 3 3.
PAGE 13
LTC6244 TYPICAL PERFORMANCE CHARACTERISTICS 0.1Hz to 10Hz Voltage Noise Series Output Resistance and Overshoot vs Capacitive Load Noise Current vs Frequency 1000 60 TA = 25°C VS = ±2.5V VCM = 0V VOUT = 100mV VS = ±2.5V AV = –2 50 30pF 100 40 OVERSHOOT (%) NOISE CURRENT (fA/√Hz) VOLTAGE NOISE (500nV/DIV) VS = 5V, 0V 10 1k 30 RS = 10Ω – + 500Ω RS CL 20 1 10 RS = 50Ω 0.1 100 TIME (1s/DIV) 0 1k 10k FREQUENCY (Hz) 6244 G28 60 50 1k 30 – + VOUT = 100mV VS = ±2.
PAGE 14
LTC6244 TYPICAL PERFORMANCE CHARACTERISTICS –30 –30 –40 –50 –60 RL = 1k, 2ND –70 RL = 1k, 3RD –80 VS = ±5V AV = +1 VOUT = 2VP-P –40 –50 –60 RL = 1k, 2ND –70 –80 –90 –90 –100 10k 100k 1M FREQUENCY (Hz) 10M DISTORTION (dBc) VS = ±2.
PAGE 15
LTC6244 APPLICATIONS INFORMATION Ampliﬁer Characteristics ESD Figure 1 is a simpliﬁed schematic of the LTC6244, which has a pair of low noise input transistors M1 and M2. A simple folded cascode Q1, Q2 and R1, R2 allow the input stage to swing to the negative rail, while performing level shift to the Differential Drive Generator. Low offset voltage is accomplished by laser trimming the input stage. The LTC6244 has reverse-biased ESD protection diodes on all input and outputs as shown in Figure 1.
PAGE 16
LTC6244 APPLICATIONS INFORMATION resistance of the particular application. Speciﬁcally, these ampliﬁers exhibit the noise of a 4k resistor, meaning it is desirable to keep the source and feedback resistance at or below this value, i.e., RS + RG||RFB ≤ 4k. Above this total source impedance, the noise voltage is not dominated by the ampliﬁer. In low gain conﬁgurations and with RF and RS in even the kilohm range (Figure 3), this pole can create excess phase shift and possibly oscillation.
PAGE 17
LTC6244 APPLICATIONS INFORMATION Large Area Photodiode Ampliﬁers A simple large area photodiode ampliﬁer is shown in Figure 4a. The capacitance of the photodiode is 3650pF (nominally 3000pF), and this has a signiﬁcant effect on the noise performance of the circuit. For example, the photodiode capacitance at 10kHz equates to an impedance of 4.36kΩ, so the op amp circuit with 1MΩ feedback has a noise gain of NG = 1 + 1M/4.36k = 230 at that frequency.
PAGE 18
LTC6244 APPLICATIONS INFORMATION CF 0.25pF CF 0.25pF 5V RF 1M 5V IPD – HAMAMATSU LARGE AREA PHOTODIODE S1227-1010BQ CPD = 3000pF 1/2 LTC6244HV VOUT = 1M • IPD BW = 350kHz OUTPUT NOISE = 220nV/√Hz AT10kHz VOUT PHILIPS BF862 JFET RF 1M 5V 4.99k – –5V 4.7μF X7R + 1/2 LTC6244HV IPD + 4.99k –5V –5V VBB 6244 F04a OUTPUT NOISE (200nV/√Hz/DIV) Figure 5a.
PAGE 19
LTC6244 APPLICATIONS INFORMATION Small Area Photodiode Ampliﬁers Small area photodiodes have very low capacitance, typically under 10pF and some even below 1pF. Their low capacitance makes them more approximate current sources to higher frequencies than large area photodiodes. One of the challenges of small area photodiode ampliﬁer design is to maintain low input capacitance so that voltage noise does not become an issue and current noise dominates.
PAGE 20
LTC6244 APPLICATIONS INFORMATION Total capacitance at the ampliﬁer’s input is now one CCM (2.1pF) plus the photodiode capacitance CPD (1.8pF), or about 4pF accounting for parasitics. The shunt impedance at 1MHz, for example, is XC = 1/(2πfC) = 39.8kΩ, and therefore, the noise gain at 1MHz is NG = 1+Rf/XC = 26. The input voltage noise of this ampliﬁer is about 15nV/√Hz, after accounting for the effects of R1 through R3, the noise of the second stage and the fact that voltage noise does rise with frequency.
PAGE 21
LTC6244 + 1/2 LTC6244 – VIN+ RIN 2k RG 10k 2k + VOUT CF 33pF 2k CIN 82pF VIN– CIN 82pF RG 10k RIN 2k CF 33pF 1/2 LTC6244 6244 F09a VOUT– + V– Figure 9a. Low Noise Fully Differential Buffer/Ampliﬁer (f–3dB = 970kHz, Gain = 5, RIN = 4k) Input Impedance = 2 • RIN VOUT + – VOUT – R = G RIN VIN + – VIN – 5MHz Maximum Gain = f3dB 1 4398 • f3dB • (Gain + 2) Gain + 2 8.
PAGE 22
LTC6244 APPLICATIONS INFORMATION C1 47pF R2 20k R1 2k V1 – VOUT 1/2 LTC6244 + C3 1000pF V+ R5 200k – R3 2k R4 20k V2 1/2 LTC6244 C2 47pF + VREF 6244 F11a VOUT = GAIN • ( V2 – V1) + VREF R2 R3 = R1, R4 = R2, C1= C2 R1 BANDWIDTH = fHI – fLO GAIN = fHI = 1 1 ,f = 2 • π • R2 • C1 LO 2 • π • R5 • C3 INPUT REFERRED NOISE (nV/√Hz) Figure 11a.
PAGE 23
LTC6244 PACKAGE DESCRIPTION DD Package 8-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1698 Rev C) R = 0.125 TYP 5 0.70 ±0.05 3.5 ±0.05 1.65 ±0.05 2.10 ±0.05 (2 SIDES) 3.00 ±0.10 (4 SIDES) PACKAGE OUTLINE 0.40 ± 0.10 8 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (NOTE 6) (DD8) DFN 0509 REV C 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.200 REF 0.75 ±0.05 4 0.25 ± 0.05 1 0.50 BSC 2.38 ±0.10 0.00 – 0.
PAGE 24
LTC6244 MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev F) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 0.42 ± 0.038 (.0165 ± .0015) TYP 8 7 6 5 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) DETAIL “A” 0° – 6° TYP GAUGE PLANE 1 0.53 ± 0.152 (.021 ± .006) DETAIL “A” 2 3 4 1.10 (.043) MAX 0.86 (.034) REF 0.18 (.
PAGE 25
LTC6244 REVISION HISTORY REV DATE DESCRIPTION B 12/09 Change to Figure 2 (Revision history begins at Rev B) PAGE NUMBER 15 6244fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PAGE 26
LTC6244 TYPICAL APPLICATION Ultralow Noise Large Area Photodiode Ampliﬁer 5V 5V –5V Photodiode Ampliﬁer Output Noise Spectal Density J4 R4 J2 5V R3 RF 1M J1 VOUT = 1M • IPD BW = 400kHz NOISE = 150μVRMS MEASURED ON 100kHz BANDWIDTH VOUT R2 5V R1 – C1 C2 C3 C4 IPD 1/2 LTC6244HV + R5 4.99k HAMAMATSU LARGE AREA PHOTODIODE S1227-1010BQ CPD = 3000pF –5V 6244 TA02a –5V OUTPUT NOISE (200nV/√Hz/DIV) CF 0.25pF J3 5V 1 C1 TO C4: 4.7μF X7R J1 TO J4: PHILIPS BF862 JFETS R1 TO R4: 4.