Datasheet

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LT6236/LT6237/LT6238

623637fa

For more information www.linear.com/LT6236

TYPICAL APPLICATION

FEATURES DESCRIPTION

Rail-to-Rail Output

215MHz, 1.1nV/√Hz

Op Amp/SAR ADC Driver

The LT

6236/LT6237/LT6238 are single/dual/quad low

noise, rail-to-rail output op amps that feature 1.1nV/√Hz

input referred noise voltage density and draw only 3.5mA

of supply current per amplifier. These amplifiers combine

very low noise and supply current with a 215MHz gain

bandwidth product and a

70V/µs slew rate. Low noise, fast

settling time and low offset voltage make this amplifier

optimal to drive low noise, high speed SAR ADCs. The

LT6236 includes a shutdown feature that can be used to

reduce the supply current to less than 10µA.

This amplifier family has an output that swings within

50mV of either supply rail to maximize the signal dynamic

range in low

supply applications and is specified on 3.3V,

5V and ±5V supplies.

The LT6236/LT6237/LT6238 are upgrades to the LT6230/

LT6231/LT6232, offering similar performance with reduced

wideband noise beyond 100kHz.

Differentially Driving a SAR ADC LT6237 Driving LTC2389-18 f

= 2kHz,

–1dBFS, 32768-Point FFT

APPLICATIONS

Low Noise: 1.1nV/√Hz

Low Supply Current: 3.5mA/Amp Max

Low Offset Voltage: 350µV Max

Fast Settling Time: 570ns to 18-Bit, 2V

P-P

Output

Low Distortion: THD = –116.8dB at 2kHz

Wide Supply Range: 3V to 12.6V

Output Swings Rail-to-Rail

215MHz Gain-Bandwidth Product

Specified Temperature Range: –40°C to 125°C

LT6236 Shutdown to 10µA Max

LT6236 in Low Profile (1mm) ThinSOT™ Package

Dual LT6237 in 3mm × 3mm 8-Lead DFN and 8-Lead

MSOP Packages

LT6238 in 16-Lead SSOP Package

16-Bit and 18-Bit SAR ADC Drivers

Active Filters

Low Noise, Low Power Signal Processing

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

ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property

of their respective owners.

623637 TA01a

–

= 6V

270pF

38.3Ω

LOWPASS FILTERS

LTC2389-18

270pF

49.9Ω

18-BIT

2.5Msps

–

1/2 LT6237

–

= –2V

FREQUENCY (MHz)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

AMPLITUDE (dBFS)

62367 TA01b

–150

–140

–130

–120

–110

–100

–90

–80

–70

–60

–50

–40

–30

–20

–10

1.2

OUT

= 7.3V

P-P

HD2 = –129.5dBc

HD3 = –118.7dBc

SFDR = 117.7dB

THD = –116.8dB

SNR = 99.7dB

SINAD = 98.9dB

Summary of content (26 pages)

PAGE 1
LT6236/LT6237/LT6238 Rail-to-Rail Output 215MHz, 1.1nV/√Hz Op Amp/SAR ADC Driver DESCRIPTION FEATURES n n n n n n n n n n n n n Low Noise: 1.1nV/√Hz Low Supply Current: 3.5mA/Amp Max Low Offset Voltage: 350µV Max Fast Settling Time: 570ns to 18-Bit, 2VP-P Output Low Distortion: THD = –116.8dB at 2kHz Wide Supply Range: 3V to 12.
PAGE 2
LT6236/LT6237/LT6238 ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (V+ to V–)............................... 12.6V Input Current (Note 2).......................................... ±40mA Output Short-Circuit Duration (Note 3)............. Indefinite Operating Temperature Range (Note 4)... –40°C to125°C Specified Temperature Range (Note 5).....–40°C to125°C Maximum Junction Temperature........................... 150°C Storage Temperature Range...................
PAGE 3
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS ENABLE = 0V, unless otherwise noted. SYMBOL PARAMETER VOS TA = 25°C, VS = 5V, 0V; VS = 3.3V, 0V; VCM = VOUT = half supply, CONDITIONS TYP MAX UNIT 100 50 75 500 350 450 µV µV µV 100 600 µV 5 10 µA IB Match (Channel-to-Channel) (Note 6) 0.1 0.9 µA Input Offset Current 0.1 0.
PAGE 4
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS ENABLE = 0V, unless otherwise noted. SYMBOL PARAMETER VL VH TA = 25°C, VS = 5V, 0V; VS = 3.3V, 0V; VCM = VOUT = half supply, CONDITIONS MIN TYP ENABLE Pin Input Voltage Low MAX 0.3 V 10 µA V+ – 0.35V ENABLE Pin Input Voltage High UNIT V Output Leakage Current ENABLE = V+ – 0.35V, VO = 1.5V to 3.5V 0.
PAGE 5
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the 0°C < TA < 70°C temperature range. VS = 5V, 0V; VS = 3.3V, 0V; VCM = VOUT = half supply, ENABLE = 0V, unless otherwise noted.
PAGE 6
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the –40°C < TA < 85°C temperature range. VS = 5V, 0V; VS = 3.3V, 0V; VCM = VOUT = half supply, ENABLE = 0V, unless otherwise noted.
PAGE 7
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the –40°C < TA < 125°C temperature range. VS = 5V, 0V; VS = 3.3V, 0V; VCM = VOUT = half supply, ENABLE = 0V, unless otherwise noted.
PAGE 8
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS TA = 25°C, VS = ±5V, VCM = VOUT = 0V, ENABLE = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage LT6236 LT6237MS8, LT6238GN LT6237DD8 MIN Input Offset Voltage Match (Channel-to-Channel) (Note 6) IB MAX UNITS 100 50 75 500 350 450 µV µV µV 100 600 µV 5 10 µA IB Match (Channel-to-Channel) (Note 6) 0.1 0.9 µA IOS Input Offset Current 0.1 0.6 µA Input Noise Voltage 0.
PAGE 9
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the 0°C < TA < 70°C temperature range. VS = ±5V, VCM = VOUT = 0V, ENABLE = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage LT6236 LT6237MS8, LT6238GN LT6237DD8 Input Offset Voltage Match (Channel-to-Channel) (Note 6) TYP MAX UNITS l l l 600 450 550 µV µV µV l 800 µV 2.2 1.8 2.2 2.
PAGE 10
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the –40°C < TA < 85°C temperature range. VS = ±5V, VCM = VOUT = 0V, ENABLE = 0V, unless otherwise noted.
PAGE 11
LT6236/LT6237/LT6238 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the –40°C < TA < 125°C temperature range. VS = ±5V, VCM = VOUT = 0V, ENABLE = 0V, unless otherwise noted.
PAGE 12
LT6236/LT6237/LT6238 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Supply Voltage (Per Amplifier) VOS Distribution 6 200 VS = ±2.5V 180 VCM = 0V MS8 160 2.0 120 100 80 60 40 4 TA = 125°C 3 TA = 25°C 2 TA = –55°C OFFSET VOLTAGE (mV) 140 1 0 0 2 4 8 10 12 6 TOTAL SUPPLY VOLTAGE (V) Input Bias Current vs Common Mode Voltage 10 TA = –55°C TA = 125°C TA = 25°C 2 10 8 0 4 5 3 2 COMMON MODE VOLTAGE (V) 1 7 VCM = 4V 6 VCM = 1.
PAGE 13
LT6236/LT6237/LT6238 TYPICAL PERFORMANCE CHARACTERISTICS Open-Loop Gain Open-Loop Gain 2.5 2.0 1.5 RL = 1k 0 RL = 100Ω –0.5 –1.0 INPUT VOLTAGE (mV) INPUT VOLTAGE (mV) 0.5 1.0 0.5 RL = 1k 0 RL = 100Ω –0.5 –1.0 0.5 –0.5 –1.5 –2.0 –2.0 –2.5 –2.5 1 1.5 2 OUTPUT VOLTAGE (V) 2.5 3 30 0.5 0 TA = 25°C –0.5 TA = 125°C –1.0 –1.5 100 26 VS = ±5V TOTAL NOISE (nV/√Hz) TA = –55°C 1.0 24 22 VS = ±2.5V 20 VS = ±1.5V 18 16 VS = ±2.
PAGE 14
LT6236/LT6237/LT6238 TYPICAL PERFORMANCE CHARACTERISTICS Gain Bandwidth and Phase Margin vs Temperature CL = 5pF RL = 1k VCM = VS/2 GAIN BANDWIDTH (MHz) –100nV 5s/DIV VS = ±5V 50 VS = 3V, 0V 240 40 VS = ±5V 220 200 VS = 3V, 0V 180 GAIN BANDWIDTH 65 35 5 TEMPERATURE (°C) 95 GAIN BANDWIDTH 180 10M 100M FREQUENCY (Hz) 1G 160 VS = ±5V FALLING 90 80 VS = ±5V RISING 70 60 40 VS = 5V, 0V 100 100 50 –80 Output Impedance vs Frequency 1k VS = ±2.5V FALLING VS = ±2.
PAGE 15
LT6236/LT6237/LT6238 TYPICAL PERFORMANCE CHARACTERISTICS Series Output Resistance and Overshoot vs Capacitive Load 40 40 VS = 5V, 0V 45 AV = 2 OVERSHOOT (%) 30 RS = 20Ω 20 15 RS = 50Ω RL = 50Ω 10 30 RS = 20Ω 25 20 15 RS = 50Ω RL = 50Ω 10 5 0 35 5 10 100 CAPACITIVE LOAD (pF) 0 1000 150 15 SETTLING RESIDUE 1 DIV = 18-BIT ERROR 0 1 –15 VOUT –30 SETTLING TIME (ns) OUTPUT VOLTAGE (V) 30 SETTLING RESIDUE (µV) 200 4 0 –60 62367 G27a Settling Time vs Output Step (Inverting) – VO
PAGE 16
LT6236/LT6237/LT6238 TYPICAL PERFORMANCE CHARACTERISTICS –40 –40 VS = ±2.5V AV = 1 VOUT = 2VP-P RL = 1k 125°C 85°C 25°C –40°C –60 –70 –80 –90 –60 –100 Harmonic Distortion (HD2) vs Frequency –40 VS = ±2.
PAGE 17
LT6236/LT6237/LT6238 TYPICAL PERFORMANCE CHARACTERISTICS Large-Signal Response Small-Signal Response 50mV/DIV 1V/DIV 2V 0V 0V –2V 200ns/DIV VS = ±2.5V AV = –1 RL = 1k 62367 G35 VS = ±2.5V AV = 1 RL = 1k Output Overdrive Recovery 0V –5V 200ns/DIV VIN 1V/DIV 2V/DIV 5V 0V VOUT 2V/DIV Large-Signal Response VS = ±5V AV = 1 RL = 1k 62367 G36 200ns/DIV 0V 62367 G37 VS = ±2.5V AV = 3 200ns/DIV 62367 G38 (LT6236) ENABLE Characteristics ENABLE Pin Current vs ENABLE Pin Voltage 30 4.
PAGE 18
LT6236/LT6237/LT6238 APPLICATIONS INFORMATION +V Q3 –V +V DESD1 Q4 C1 DESD2 Q1 D1 DESD5 VOUT DESD6 DIFFERENTIAL DRIVE GENERATOR –V –VIN Q5 CM +V –V Q2 Q6 D2 +V +VIN DESD3 DESD4 –V I1 BIAS ENABLE +V –V 62367 F01 Figure 1. Simplified Schematic Figure 1 is a simplified schematic of the LT6236/LT6237/ LT6238, which has a pair of low noise input transistors Q1 and Q2.
PAGE 19
LT6236/LT6237/LT6238 APPLICATIONS INFORMATION ESD The LT6236/LT6237 have reverse-biased ESD protection diodes on all inputs and outputs as shown in Figure 1. If these pins are forced beyond either supply, unlimited current will flow through these diodes. If the current is transient and limited to 100mA or less, no damage to the device will occur.
PAGE 20
LT6236/LT6237/LT6238 APPLICATIONS INFORMATION Interfacing to ADCs When driving an ADC, a single-pole, passive RC filter should be used between the outputs of the LT6236/LT6237/LT6238 and the inputs of the ADC. The sampling process of ADCs creates a charge transient from the switching of the ADC sampling capacitor. This momentarily “shorts” the output of the amplifier as charge is transferred between amplifier and sampling capacitor.
PAGE 21
LT6236/LT6237/LT6238 TYPICAL APPLICATIONS Single Supply, Low Noise, Low Power, Bandpass Filter with Gain = 10 Frequency Response Plot of Bandpass Filter 23 C2 47pF f0 = V+ 1 = 1MHz 2πRC GAIN (dB) R1 732Ω C = √C1C2, R = R1 = R2 C1 1000pF VIN R3 10k R2 732Ω ( – LT6236 + R4 10k C3 0.1µF ) f0 = 732Ω MHz, MAXIMUM f0 = 1MHz R f–3dB = f0 2.5 AV = 20dB at f0 EN = 4µVRMS INPUT REFERRED IS = 3.7mA FOR V+ = 5V 0.
PAGE 22
LT6236/LT6237/LT6238 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 1.50 – 1.75 (NOTE 4) 2.80 BSC 1.4 MIN 3.85 MAX 2.62 REF PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 1.90 BSC 0.09 – 0.
PAGE 23
LT6236/LT6237/LT6238 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev G) 0.889 ±0.127 (.035 ±.005) 5.10 (.201) 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 ±.
PAGE 24
LT6236/LT6237/LT6238 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641 Rev B) .189 – .196* (4.801 – 4.978) .045 ±.005 16 15 14 13 12 11 10 9 .254 MIN .009 (0.229) REF .150 – .165 .229 – .244 (5.817 – 6.198) .0165 ±.0015 .150 – .157** (3.810 – 3.988) .0250 BSC RECOMMENDED SOLDER PAD LAYOUT 1 .015 ±.004 × 45° (0.38 ±0.10) .007 – .0098 (0.178 – 0.
PAGE 25
LT6236/LT6237/LT6238 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 09/13 Added LT6238 quad All 623637fa 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 its circuits as described herein will not infringe on existing patent rights. Forofmore information www.linear.
PAGE 26
LT6236/LT6237/LT6238 TYPICAL APPLICATION The LT6236 is configured as a transimpedance amplifier with an I-to-V conversion gain of 1.5kΩ set by R1. The LT6236 is ideally suited to this application because of its low input offset voltage and current, and its low noise. This is because the 1.5k resistor has an inherent thermal noise of 5nV/√Hz or 3.4pA/√Hz at room temperature, while the LT6236 contributes only 1.1nV/√Hz and 2.4pA/√Hz.