LM2907-N Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

PDIP-8

Physical pin numbers8 pins

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LM2907-N pin functions and connections
Signal	Type	Function & connection
TACH+	Ground-crossing signal input	The input comparator detects alternating positive and negative excursions relative to ground. Connection guidance Apply a 1 kHz sine wave with 1 V peak amplitude and zero DC offset in the example. The eight-pin part needs both polarities; an ordinary 0–5 V logic waveform is not a direct substitute.
CP1	Pump timing capacitor	An internal current charges and discharges C1 on alternate input half cycles. Connection guidance Connect C1 = 1 nF to GND. Keep C1 above 500 pF for accurate operation and internal compensation.
CP2 / IN+	Filtered charge-pump output	Mirrored current pulses feed R1 and C2. This node is also the amplifier noninverting input in the eight-pin device. Connection guidance Connect 100 kΩ and 1 µF in parallel to GND. The pump output is a current-producing node, not a rail-to-rail logic signal.
EMIT	Output transistor emitter	Buffered output in the voltage-follower connection. Connection guidance Join to IN−7, a high-impedance voltmeter and a 10 kΩ load to GND.
COL	Output transistor collector	Separate collector of the internal amplifier output transistor. Connection guidance Join to the +12 V supply for the emitter-follower example. COL is not internally tied to V+.
V+	Device supply	Powers the input comparator, charge pump and amplifier. Connection guidance Use a regulated +12 V rail with 100 nF and local bulk bypass to GND. Conversion gain is proportional to this supply; LM2907 has no LM2917-style internal Zener regulator.
IN−	Amplifier inverting input	Negative-feedback input for the output amplifier. Connection guidance Connect directly to EMIT4 for unity-gain buffering. CP2 / IN+3 and IN−7 must remain within the amplifier common-mode region.
TACH− / GND	Ground and input reference	Internally connects the negative tachometer input to device ground in the eight-pin variant. Connection guidance Connect externally to circuit GND, including the signal-generator return. The internal connection does not eliminate the external ground connection.

Operating context

Selected eight-pin devices

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Example supply	12 V regulated	Datasheet electrical-characteristic test supply
Operating temperature	−40 to +85°C	Selected orderable-device grade
Amplifier common-mode input	0 to VCC − 1.5 V	Electrical table at 12 V and 25°C
Supply current	3.8 mA typical; 6 mA maximum	Manufacturer electrical test conditions
Supply / collector stress limit	28 V absolute maximum	Not a normal operating target
Storage temperature	−65 to +150°C	Unpowered

Supply variation changes the conversion gain; select a clean, stable rail.

Input and charge pump

12 V, 25°C reference conditions

Manufacturer-referenced values7 parameters

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Parameter	Value	Conditions / notes
Input thresholds	±25 mV typical; ±10 to ±40 mV specified	250 mV peak-to-peak input at 1 kHz
Input hysteresis	30 mV typical	Manufacturer threshold test
Eight-pin input offset	5 mV typical; 15 mV maximum	Manufacturer threshold test
Charge/discharge current	180 µA typical; 140–240 µA	CP1 / CP2 at 6 V
Pump voltage excursion	Approximately VCC / 2	Difference between C1 charge and discharge levels
Conversion constant K	1 typical; 0.9–1.1 specified	VOUT = K × VCC × f × C1 × R1
C1 selection	Greater than 500 pF for accurate operation	Example uses 1 nF

Do not drive the eight-pin input with a waveform that never crosses ground.

Output amplifier

Separate collector and emitter

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Input offset	3 mV typical; 10 mV maximum	VIN = 6 V
Input bias	50 nA typical; 500 nA maximum	VIN = 6 V
Output source current	10 mA minimum	Emitter at VCC − 2 V
Output sink current	40 mA minimum; 50 mA typical	Collector at 1 V
Follower configuration	COL to supply; EMIT to IN−	Example uses a high-impedance meter and 10 kΩ load
Example load at 1 kHz	1.2 V / 10 kΩ = 0.12 mA	Nominal settled value

Source and sink capabilities are specified under different conditions; do not assume 50 mA is guaranteed in both directions.

12 V tachometer example

All ground symbols share one return

Manufacturer-referenced values8 parameters

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Parameter	Value	Conditions / notes
TACH+1	1 kHz sine, ±1 V peak	Zero DC offset; generator return to GND8
CP1 pin 2	C1 = 1 nF to GND	Sets charge transferred per cycle
CP2 / IN+ pin 3	R1 = 100 kΩ and C2 = 1 µF to GND	Parallel averaging network
EMIT4 and IN−7	Join as VOUT	Unity-gain buffer feedback
COL5 and V+6	+12 V	Output transistor and controller share the bench supply
GND8	Circuit return	Mandatory external connection
Supply bypass	100 nF + 10 µF to GND	Close to V+6 and GND8
Output load	10 kΩ to GND plus voltmeter	Keep the instrument high impedance

No microcontroller or firmware is required. This is an illustrative reference circuit, not a live simulation.

Scale, ripple and response

Nominal example · K = 1

Manufacturer-referenced values8 parameters

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Parameter	Value	Conditions / notes
Conversion equation	VOUT ≈ K × VCC × fIN × C1 × R1	Subject to pump current, amplifier range and tolerances
Scale	1.2 mV / Hz	12 V × 1 nF × 100 kΩ
500 Hz / 1 kHz / 5 kHz	0.6 V / 1.2 V / 6 V	Settled illustrative readings
Average current at 1 kHz	12 µA	VCC × fIN × C1
Filter time constant	100 ms	100 kΩ × 1 µF
Approximate 1% settling	About 0.46 s	4.6 RC for an ideal first-order filter
Pump ripple at 1 kHz	About 5.6 mV peak-to-peak	Datasheet approximation with I2 = 180 µA
Stopped input	Output decays toward zero	The filter prevents an instantaneous step

These are calculated values. Capacitor/resistor tolerances, K, supply stability and amplifier errors affect the measured result.

Accuracy and design limits

Keep the operating point in range

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Typical linearity	0.3%	TI test network: C1 = 1 nF, R1 = 68 kΩ, C2 = 0.22 µF
Specified nonlinearity	−1% to +1%	5 kHz deviation from line through 1 and 10 kHz test points
Gain error	K is specified 0.9–1.1	Typical linearity is not total absolute accuracy
Larger C2	Less ripple, slower response	It does not change ideal DC gain
Larger R1 or C1	More volts per hertz	May reduce usable frequency/output range
Supply sensitivity	Output scale follows VCC	Use regulation or calibrate the complete system

The 100 kΩ example differs from the linearity test network; its total accuracy is not claimed to equal that test result.

Package selection

LM2907N-8/NOPB · PDIP-8

Manufacturer-referenced values5 parameters

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Parameter	Value	Conditions / notes
Through-hole	LM2907N-8/NOPB · PDIP-8	2.54 mm pitch; 7.62 mm nominal rows
Surface mount	LM2907M-8/NOPB · SOIC-8	1.27 mm pitch; narrow body
Fourteen-pin variants	Different map and internal connections	Not represented by these eight-pin views
LM2917 distinction	Adds an internal Zener regulator	Do not import its regulator limits into LM2907
Footprint provenance	Original editable TEP land patterns	Verify the exact ordered package and fabricator rules

Pin functions and physical numbering stay consistent when switching between the two selected packages.