Features Guaranteed linearity 0.01% max Improved performance in existing voltage-to-frequency conversion applications Split or single supply operation Operates on single 5V supply Pulse output compatible with all logic forms Excellent temperature stability: ±50 ppm/°C max Low power consumption: 15 mW typical at 5V Wide dynamic range, 100 dB min at 10 kHz full scale frequency Wide range of full scale frequency: 1 Hz to 100 kHz Low cost Description The LM231/LM331 family of voltage-to-frequency converters are ideally suited for use in simple low-cost circuits for analog-to-digital conversion, precision frequency-to-voltage conversion, long-term integration, linear frequency modulation or demodulation, and many other functions. The output when used as a voltage-to-frequency converter is a pulse train at a frequency precisely proportional to the applied input voltage. Thus, it provides all the inherent advantages of the voltage-to-frequency conversion techniques, and is easy to apply in all standard voltage-to-frequency converter applications. Further, the LM231A/LM331A attain a new high level of accuracy versus temperature which could only be attained with expensive voltage-to-frequency modules. Additionally the LM231/331 are ideally suited for use in digital systems at low power supply voltages and can provide low-cost analog-to-digital conversion in microprocessor-controlled systems. And, the frequency from a battery powered voltage-to-frequency converter can be easily channeled through a simple photo isolator to provide isolation against high common mode levels. The LM231/LM331 utilize a new temperature-compensated band-gap reference circuit, to provide excellent accuracy over the full operating temperature range, at power supplies as low as 4.0V. The precision timer circuit has low bias currents without degrading the quick response necessary for 100 kHz voltage-to-frequency conversion. And the output are capable of driving 3 TTL loads, or a high voltage output up to 40V, yet is short-circuit-proof against VCC.

Typical Application click for larger image	Block Diagram click for larger image
Typical Performance click for larger image

Datasheets

Title		Size	Date	Other Language
	LM231 Precision Voltage-to-Frequency Converter	811 Kbytes	26-Apr-06

Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Pack Size
LM231AN/NOPB LM231AN RoHS Status	MDIP	Full production Lead Time: 6 weeks	Distributor Region Qty ARROW Worldwide 30 AVNET-EM Worldwide 130 CEAC Asia Pacific 400 DIGI-KEY Worldwide 76 FARNELL Europe and Asia 25 MOUSER Worldwide 140 NEWARK Americas 62 TAYLOR Americas 30	$4.38 each at 1K+ pcs	rail of 40
LM231N/NOPB LM231N RoHS Status	MDIP	Full production Lead Time: 6 weeks	Distributor Region Qty ARROW Worldwide 82 AVNET-EM Worldwide 83 CEAC Asia Pacific 200 DIGI-KEY Worldwide 339 FARNELL Europe and Asia 1003 MOUSER Worldwide 131 NEWARK Americas 81 RS COMPONENTS Worldwide 113 RSL MICRO Asia Pacific 320 TAYLOR Americas 711	$2.58 each at 1K+ pcs	rail of 40

Obsolete Versions

Obsolete Part	Alternate Part or Supplier	Source	Last Time Buy Date
LM231WM	NONE	NONE	08 Sep 1998
LM231WMX	NONE	NONE	08 Sep 1998

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM231.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM231 is located at RoHS Status.

Part Number(s) (NSID)	Weight (milligrams)	Type	Pins	MSL Rating	Peak Reflow	RoHS Status	CAD Symbols	Models	Package Marking Format
LM231AN/NOPB LM231AN	508.252 510.002	MDIP	8	1 1	NA NA	Detail	N/A	N/A	NSUZXYTTE# LM 231AN
LM231N/NOPB LM231N	508.252 510.002	MDIP	8	1 1	NA NA	Detail	N/A	N/A	NSUZXYTTE# LM 231N

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM231.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM231 is located at RoHS Status.

CAD Symbols and Models N/A

Models N/A

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM231AN	SLM	0	44046	0	0	3532500	1	1002356520
LM231N	SLM	0	44046	0	0	3532500	1	1002356520

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM231.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM231 is located at RoHS Status.

Obsolete Versions

Obsolete Part	Alternate Part or Supplier	Source	Last Time Buy Date
LM231WM	NONE	NONE	08 Sep 1998
LM231WMX	NONE	NONE	08 Sep 1998