Linear Technology LTC1065MJ8, LTC1065CS, LTC1065CN8, LTC1065 Datasheet

FEATURES

■Clock-Tunable Cutoff Frequency

■1mV DC Offset (Typical)

■80dB CMR (Typical)

■Internal or External Clock

■50μVRMS Clock Feedthrough

■100:1 Clock-to-Cutoff Frequency Ratio

■80μVRMS Total Wideband Noise

■0.004% Noise + THD at 2VRMS Output Level

■50kHz Maximum Cutoff Frequency

■Cascadable for Faster Roll-Off

■Operates from ±2.375 to ±8V Power Supplies

■Self-Clocking with 1 RC

APPLICATIOUS

■Audio

■Strain Gauge Amplifiers

■Anti-Aliasing Filters

■Low Level Filtering

■Digital Voltmeters

■Smoothing Filters

■Reconstruction Filters

TYPICAL APPLICATIOU

3.4kHz Single 5V Supply Bessel Lowpass Filter

		5V
		4.99k	VIN	1		8
+				2		7	VOUT
	1μF				LTC1065
		4.53k	0.1μF	3		6	5V
	TANT
				4		5	0.1μF
					13k*		200pF*
		* SELF-CLOCKING SCHEME					1065 TA01

LTC1065

DC Accurate, Clock-Tunable Linear Phase 5th Order Bessel Lowpass Filter

DESCRIPTIOU

The LTC1065 is the first monolithic filter providing both clock-tunability with low DC output offset and over 12-bit DC accuracy. The frequency response of the LTC1065 closely approximates a 5th order Bessel polynomial. With appropriate PCB layout techniques the output DC offset is typically 1mV and is constant over a wide range of clock frequencies. With ±5V supplies and ±4V input voltage range, the CMR of the device is typically 80dB.

The filter cutoff frequency is controlled either by an internal or external clock. The clock-to-cutoff frequency ratio is 100 : 1. The on-board clock is nearly power supply independent and it is programmed via an external RC. The 50μVRMS clock feedthrough of the device is considerably lower than other existing monolithic filters.

The LTC1065 wideband noise is 80μVRMS and it can process large AC input signals with low distortion. With

± 7.5V supplies, for instance, the filter handles up to 4VRMS (94dB S/N ratio) while the standard 1kHz THD is below 0.005%; 87dB dynamic range (S/N + THD) is obtained with input levels between 2VRMS and 2.5VRMS.

The LTC1065 is available in 8-pin miniDIP and 16-pin SOL. For a Butterworth response, see LTC1063 data sheet. The LTC1065 is pin compatible with the LTC1063.

Frequency Response

		10
		0
		–10
		–20
	(dB)	–30
		–40
	GAIN
		–50
		–60
		–70
		–80
		–90

1 10 100 FREQUENCY (kHz)

1065 TA02

1

LTC1065

ABSOLUTE WAXIWUW	RATIUGS
Total Supply Voltage (V + to V –) ..........................	16.5V
Power Dissipation.............................................	400mW
Voltage at Any Input .... (V – – 0.3V) ≤ VIN ≤ (V+ + 0.3V)
Burn-In Voltage ......................................................	16V
Storage Temperature Range ................	– 65°C to 150°C

Operating Temperature Range	– 40°C to 85°C
LTC1065C..........................................
LTC1065M .......................................	– 55°C to 125°C
Lead Temperature (Soldering, 10 sec).................	300°C

PACKAGE/ORDER IUFORWATIOU

		TOP VIEW
VIN				VOS ADJ
	1		8
GND				VOUT
	2		7
V–				V+
	3		6
CLK OUT				CLK IN
	4		5

J8 PACKAGE

8-LEAD CERAMIC DIP

N8 PACKAGE

8-LEAD PLASTIC DIP

TJMAX = 150°C, θJA = 100°C/W (J) TJMAX = 100°C, θJA = 110°C/W (N)

ORDER PART

NUMBER

LTC1065CN8

LTC1065MJ8

			TOP VIEW
NC
	1			16	VOS ADJ
VIN
	2			15	NC
GND
	3			14	VOUT
NC	4			13	NC
V–					V+
	5			12
NC	6			11	NC
NC	7			10	NC
CLK OUT	8			9	CLK IN

S PACKAGE

16-LEAD PLASTIC SOL

TJMAX = 100°C, θJA = 85°C/W

ORDER PART

NUMBER

LTC1065CS

ELECTRICAL CHARACTERISTICS

VS = ±5V, fCLK = 500kHz, fC = 5kHz, RL = 10k, TA = 25°C, unless otherwise specified.

PARAMETER	CONDITIONS		MIN	TYP	MAX	UNITS
Clock-to-Cutoff Frequency Ratio (fCLK /fC)	±2.375V ≤ VS ≤ ±7.5V			100 ± 0.5
Maximum Clock Frequency (Note 1)	VS = ±7.5V			5		MHz
	VS = ±5V			4		MHz
	VS = ±2.5V			3		MHz
Minimum Clock Frequency (Note 2)	±2.5V ≤ VS ≤ ±7.5V, TA < 85°C			30		Hz
Input Frequency Range			0		0.9fCLK
Filter Gain	VS = ±5V, fCLK = 25kHz, fC = 250Hz
	fIN = 250Hz	●	– 3.5	– 3.1	– 2.7	dB
	fIN = 1kHz	●	– 43.0	– 41.0	– 39.0	dB
	VS = ±5V, fCLK = 500kHz, fC = 5kHz
	fIN = 100Hz			0		dB
	fIN = 1kHz = 0.2fC	●	– 0.215	– 0.175	– 0.135	dB
	fIN = 2.5kHz = 0.5fC	●	– 1.1	– 0.972	– 0.84	dB
	fIN = 4kHz = 0.8fC	●	– 2.35	– 2.13	– 1.9	dB
	fIN = 5kHz = fC	●	– 3.35	– 3.1	– 2.83	dB
	fIN = 10kHz = 2fC	●	– 14.63	– 14.15	– 13.7	dB
	fIN = 20kHz = 4fC	●	– 43.0	– 41.15	– 39.0	dB

2

LTC1065

ELECTRICAL CHARACTERISTICS

VS = ±5V, fCLK = 500kHz, fC = 5kHz, RL = 10k, TA = 25°C, unless otherwise specified.

PARAMETER	CONDITIONS			MIN	TYP	MAX	UNITS
Filter Gain	VS = ±2.375V, fCLK = 500kHz, fC = 5kHz
		fIN = 1kHz	●	– 0.225	– 0.185	– 0.145	dB
		fIN = 2.5kHz	●	– 1.1	– 1.0	– 0.83	dB
		fIN = 4kHz	●	– 2.35	– 2.15	– 1.9	dB
		fIN = 5kHz	●	– 3.35	– 3.1	– 2.83	dB
		fIN = 10kHz	●	– 14.63	–14.1	–13.7	dB
Clock Feedthrough	±2.375V ≤ VS ≤ ±7.5V				50		μVRMS
Wideband Noise (Note 3)	±2.375V ≤ VS ≤ ±7.5V, 1Hz < f < fCLK				80		μVRMS
THD + Wideband Noise (Note 4)	VS = ±7.5V, fC = 20kHz, fIN = 1kHz,				– 87		dB
	2VRMS ≤ VIN ≤ 2.5VRMS
Filter Output ± DC Swing	VS = ±2.375V			1.5/– 2.0	1.7/– 2.2		V
			●	1.3/– 1.8			V
	VS = ±5V			4.0/– 4.5	4.3/– 4.8		V
			●	3.8/– 4.3			V
	VS = ±7.5V			6.5/– 7.0	6.8/– 7.3		V
			●	6.3/– 6.8			V
Input Bias Current					10		nA
Dynamic Input Impedance					800		MΩ
Output DC Offset (Note 5)	VS = ±2.375V				2		mV
	VS = ±5V				0	±5	mV
	VS = ±7.5V				– 4		mV
Output DC Offset Drift	VS = ±2.375V				10		μV/°C
	VS = ±5V				20		μV/°C
	VS = ±7.5V				25		μV/°C
Self-Clocking Frequency (fOSC)	R (Pin 4 to 5) = 20k, C (Pin 5 to GND) = 470pF
	VS = ±2.375V			99	103	112	kHz
		LTC1065C	●	95	103	112	kHz
		LTC1065M	●	92	100	112	kHz
	VS = ±5V			100	106	112	kHz
		LTC1065C	●	98	106	114	kHz
		LTC1065M	●	97	105	114	khz
	VS = ±7.5V			102	106	114	kHz
		LTC1065C	●	101	109	116	kHz
		LTC1065M	●	100	108	116	kHz
External CLK Pin Logic Thresholds	VS = ±2.375V	Min Logical “1”			1.43		V
		Max Logical “0”			0.47		V
	VS = ±5V	Min Logical “1”			3		V
		Max Logical “0”			1		V
	VS = ±7.5V	Min Logical “1”			4.5		V
		Max Logical “0”			1.5		V
Power Supply Current	VS = ±2.375V, fCLK = 500kHz				2.5	4.0	mA
		LTC1065C	●			5.5	mA
		LTC1065M	●			6.0	mA
	VS = ±5V, fCLK = 500kHz				5.5	9	mA
		LTC1065C	●			11	mA
		LTC1065M	●			12	mA
	VS = ±7.5V, fCLK = 500kHz				7.0	12.0	mA
		LTC1065C	●			14.5	mA
		LTC1065M	●			16.0	mA

3

LTC1065

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range.

Note 1: The maximum clock frequency is arbitrarily defined as: the frequency at which the filter AC response exhibits ³ 1dB of gain peaking. Note 2: At limited temperature ranges (i.e., TA £ 50°C) the minimum clock frequency can be as low as 10Hz. The typical minimum clock frequency is arbitrarily defined as: the clock frequency at which the output DC offset changes by more than 1mV.

Note 3: The wideband noise specification does not include the clock feedthrough.

Note 4: To properly evaluate the filter’s harmonic distortion an inverting output buffer is recommended. An output buffer (although recommended) is not necessarily needed when measuring output DC offset or wideband noise (see Figure 3).

Note 5: The output DC offset is optimized for ±5V supply. The output DC offset shifts when the power supplies change; however this phenomenon is repeatable and predictable.

TYPICAL PERFORWAUCE CHARACTERISTICS

	Output Offset vs Clock,
Self-Clocking Frequency vs R	Low Clock Rates

	110				50
	100	LTC1065			45	VS = ±5V
	90				40	A. TA = 25°C
		4	5
TO45 (kΩ)	80	R		OFFSET(mV)	35	B. TA = 85°C	OFFSET(mV)
	60		C		25
	70	C = 200pF			30
PINSR		fOSC 1/RC		OUTPUT			OUTPUT
	40				15
	50				20
	30				10
	20				5	B
	10				0	A
		300	500			110	210
	100				10
		FREQUENCY (kHz)				EXTERNAL CLOCK FREQUENCY (Hz)
			1065 G01				1065 G02

Output Offset vs Clock,

Medium Clock Rates

5

4

VS = ±7.5V

3

2

1

VS = ±5V

0

–1

–2

–3

VS = ±2.5V

–4

–5

0	500	1000
	EXTERNAL CLOCK FREQUENCY (kHz)

1065 G03

GAIN (dB)

Gain vs Frequency; VS = ±2.5V

10

0

–10

–20

–30

–40

A

B

C

–50

A. fCLK = 0.5MHz

–60

B. fCLK = 1MHz

–70

C. fCLK = 2MHz

–80

VIN

= 750mVRMS

TA = 25°C

–90

10

1

100

200

INPUT FREQUENCY (kHz)

GAIN (dB)

Gain vs Frequency; VS = ±5V

10

0

–10

–20

–30

–40

A

B

C

D

–50

A. fCLK = 1MHz

B. fCLK = 2MHz

–60

C. fCLK = 3MHz

–70

D. fCLK = 4MHz

–80

VIN

= 1.4VRMS

TA = 25°C

–90

10

1

100

200

INPUT FREQUENCY (kHz)

GAIN (dB)

Gain vs Frequency; VS = ±7.5V

10

0			D
–10
–20	A	B C	E

–30

–40 A. fCLK = 1MHz

B.fCLK = 2MHz

–50 C. f = 3MHz

			CLK
–60			D. fCLK = 4MHz
–70			E. fCLK = 5MHz
–80			VIN	= 1.4VRMS
			TA = 25°C
–90

1	10	100	200
	INPUT FREQUENCY (kHz)

1065 G04

1065 G05

1065 G06

4