Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLTC1560-1IS8#PBF

LTC1560-1

sn15601 15601fs

1MHz/500kHz

Continuous Time,

Low Noise, Lowpass Elliptic Filter

FEATURES

■

5th Order, 1MHz Elliptic Filter in SO-8 Package

■

Pin Selectable 1MHz/500kHz Cutoff Frequency

■

Signal-to-Noise Ratio (SNR): 75dB

■

Signal-to-Noise Ratio with –63dB THD: 69dB

■

Passband Ripple (f

CUTOFF

= 1MHz): ±0.3dB

■

Stopband Attenuation Better Than 60dB

■

No External Components Required

either 500kHz (Pin 5 to V

) or 1MHz (Pin 5 to V

–

). When

programmed for 1MHz, the passband ripple is typically

±0.2dB up to 0.55f

CUTOFF

and ±0.3dB to 0.9f

CUTOFF

. The

transition band gain is –24dB at 1.4f

CUTOFF

and –51dB at

CUTOFF

. Stopband attenuation is 63dB at 2.43f

CUTOFF

and

above, remaining at least 60dB to 10MHz with proper

board layout. When the LTC1560-1 is programmed for

CUTOFF

= 500kHz, the filter response closely follows the

1MHz case with the exception of passband flatness near

the cutoff frequency; the gain at f

CUTOFF

is –1.3dB.

The LTC1560-1, unlike other high frequency filters, is

designed for low noise and low distortion. With a 1V

RMS

input signal, the signal-to-noise ratio is 69dB and the THD

is –63dB. The maximum SNR of 75dB is obtained with a

2.1V

RMS

input signal. This results in –46dB THD.

The LTC1560-1 operates with ±5V supplies, has a power

saving mode and is available in an SO-8 surface mount

package.

Other cutoff frequencies from 450kHz to 1.5MHz can be

obtained. Demo board DC135A is available for the

LTC1560-1. For more information please contact LTC

Marketing.

FREQUENCY (MHz)

0.1

–90

GAIN (dB)

–70

–50

–30

–10

110

1560-1 TA02

–80

–60

–40

–20

CUTOFF

= 1MHz/500kHz

Frequency Response

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

TYPICAL APPLICATION

DESCRIPTION

The LTC

1560-1 is a 5th order, continuous-time, lowpass

filter.

The elliptic transfer function of the LTC1560-1 was

carefully chosen to reach a compromise between selectiv-

ity, for antialiasing applications, and transient response.

The filter cutoff frequency, f

CUTOFF

, is pin selectable to

■

Antialiasing Filters

■

Smoothing or Reconstruction Filters

■

Communication Filters

APPLICATIONS

OUT

(OR –5V)

0.01µF

0.1µF

–5V

1560-1 TA01

0.01µF

–5V

1MHz

500kHz

GND

–

GND

OUT

SHDN

0.5f

LTC1560-1

1MHz/500kHz Elliptic Lowpass Filter

Summary of content (8 pages)

PAGE 1
LTC1560-1 1MHz/500kHz Continuous Time, Low Noise, Lowpass Elliptic Filter either 500kHz (Pin 5 to V +) or 1MHz (Pin 5 to V –). When programmed for 1MHz, the passband ripple is typically ±0.2dB up to 0.55fCUTOFF and ±0.3dB to 0.9fCUTOFF. The transition band gain is – 24dB at 1.4fCUTOFF and – 51dB at 2fCUTOFF. Stopband attenuation is 63dB at 2.43fCUTOFF and above, remaining at least 60dB to 10MHz with proper board layout.
PAGE 2
LTC1560-1 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION Total Supply Voltage (V + to V –) ............................. 12V Power Dissipation ............................................. 400mW Burn-In Voltage ................................................... ±5.5V Operating Temperature Range LTC1560-1C ........................................... 0°C to 70°C LTC1560-1I ....................................... – 40°C to 85°C Maximum Junction Temperature .........................
PAGE 3
LTC1560-1 U W TYPICAL PERFORMANCE CHARACTERISTICS Frequency Response 10 Frequency Response 10 fCUTOFF = 1MHz 0 0 –10 –10 fCUTOFF = 500kHz – 40 –50 0.2 –30 GAIN (dB) GAIN (dB) –30 – 40 –50 –70 –70 – 80 – 0.4 –90 – 80 0 2 1 4 3 0 – 0.6 1.0 0.5 FREQUENCY (MHz) FREQUENCY (MHz) Group Delay 1.6 Group Delay 2.25 fCUTOFF = 1MHz fCUTOFF = 500kHz fCUTOFF = 500kHz 2.00 0 1.2 1.75 – 0.4 – 0.6 – 0.8 GROUP DELAY (µs) 1.4 GROUP DELAY (µs) 0.2 – 0.2 1.0 0.8 0.6 0.4 –1.0 –1.
PAGE 4
LTC1560-1 U W TYPICAL PERFORMANCE CHARACTERISTICS Output Noise vs Frequency Transient Response Transient Response 60 54 fCUTOFF = 1MHz TOTAL OUTPUT NOISE = 232µVRMS OUTPUT NOISE (µVRMS) 1V/DIV 1V/DIV 48 fCUTOFF = 0.5MHz VIN = 5VP-P fIN = 50kHz 1560-1 G09 2µs/DIV fCUTOFF = 1MHz VIN = 5VP-P fIN = 50kHz 36 30 24 18 12 1560-1 G10 2µs/DIV 42 6 0 0.1 0.5 FREQUENCY (MHz) 1.0 1.5 1560-1 G11 Dynamic Range Output Noise vs Frequency 60 – 20 fCUTOFF = 0.
PAGE 5
LTC1560-1 U U U PIN FUNCTIONS GND (Pins 1, 3): Analog Ground Pins. The quality of the analog ground can affect the filter performance. For dual supply operation the analog ground pin should be connected to an analog ground plane surrounding the package. The analog ground plane should be connected to a digital ground plane (if any) at a single point.
PAGE 6
LTC1560-1 U W U U APPLICATIONS INFORMATION The performance of the LTC1560-1 can be easily evaluated by using demo board 135A which can be obtained through LTC marketing. Figure 2 shows the circuit connection of the LTC1560-1 in demo board 135A. The filter cutoff frequency can be switched via S2 and the power savings mode can also be activated via S1. The output of the filter is buffered by U2, an LT ®1360 op amp. The buffering can be bypassed by using jumper JP1. Figure 3 shows the demo board layout.
PAGE 7
LTC1560-1 U TYPICAL APPLICATIONS N Augmenting the LTC1560-1 for Improved Delay Flatness 40.2k 20k 22pF 5V 9.75k 1 2 VIN –5V GND VIN VOUT SHDN 7 LTC1560-1 3 GND V+ 6 4 5 V– 0.5fC /fC 22pF 6.49k 8 2 0.1µF – 1/2 LT1364 (OR – 5V) 3 6.65k 1 6 + + 49.9Ω 7 1/2 LT1364 5 5V 0.1µF – 8 VOUT 4 0.01µF 0.1µF – 5V 1560-1 TA05 0.01µF 0.
PAGE 8
LTC1560-1 U TYPICAL APPLICATION Measured Frequency Response A Simple Highpass/Lowpass Filter 15V 10 0 0.1µF 300pF 300pF 2 VIN 8.1k –5V 3 4 GND VIN VOUT SHDN LTC1560-1 GND V+ V– 0.5fC /fC 1k 8 7 3 7 LT1360 (OR – 5V) 6 + 2 – –20 8 VOUT GAIN (dB) 1 –10 4 5V 5 0.1µF –30 –40 –50 –60 0.01µF –70 0.1µF –80 0.1µF 0.01µF –15V –90 1560-1 TA07 20 100 1000 FREQUENCY (kHz) 10000 1560-1 TA08 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.