NSC LM334Z, LM334SMX, LM334SM, LM334MX, LM334M Datasheet

March 2000

LM134/LM234/LM334

3-Terminal Adjustable Current Sources

General Description

The LM134/LM234/LM334 are 3-terminal adjustable current sources featuring 10,000:1 range in operating current, excellent current regulation and a wide dynamic voltage range of 1V to 40V. Current is established with one external resistor and no other parts are required. Initial current accuracy is

±3%. The LM134/LM234/LM334 are true floating current sources with no separate power supply connections. In addition, reverse applied voltages of up to 20V will draw only a few dozen microamperes of current, allowing the devices to act as both a rectifier and current source in AC applications.

The sense voltage used to establish operating current in the LM134 is 64mV at 25ÊC and is directly proportional to absolute temperature (ÊK). The simplest one external resistor connection, then, generates a current with ≈+0.33%/ÊC temperature dependence. Zero drift operation can be obtained by adding one extra resistor and a diode.

Applications for the current sources include bias networks, surge protection, low power reference, ramp generation,

LED driver, and temperature sensing. The LM234-3 and LM234-6 are specified as true temperature sensors with guaranteed initial accuracy of ±3ÊC and ±6ÊC, respectively. These devices are ideal in remote sense applications because series resistance in long wire runs does not affect accuracy. In addition, only 2 wires are required.

The LM134 is guaranteed over a temperature range of −55ÊC to +125ÊC, the LM234 from −25ÊC to +100ÊC and the LM334 from 0ÊC to +70ÊC. These devices are available in TO-46 hermetic, TO-92 and SO-8 plastic packages.

Features

nOperates from 1V to 40V

n0.02%/V current regulation

nProgrammable from 1µA to 10mA

nTrue 2-terminal operation

nAvailable as fully specified temperature sensor

n±3% initial accuracy

Connection Diagrams

SO-8

Surface Mount Package

SO-8 Alternative Pinout

Surface Mount Package

TO-46

Metal Can Package

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Order Number LM334M or	Order Number LM334SM or
LM334MX	LM334SMX
See NS Package Number M08A	See NS Package Number M08A

TO-92 Plastic Package

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V− Pin is electrically connected to case.

Bottom View

Order Number LM134H,

LM234H or LM334H

See NS Package

Number H03H

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Bottom View

Order Number LM334Z, LM234Z-3 or LM234Z-6 See NS Package Number Z03A

Sources Current Adjustable Terminal-3 LM134/LM234/LM334

© 2000 National Semiconductor Corporation

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LM134/LM234/LM334

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

V+ to V− Forward Voltage
LM134/LM234/LM334	40V
LM234-3/LM234-6	30V
V+ to V− Reverse Voltage	20V
R Pin to V− Voltage	5V
Set Current	10 mA
Power Dissipation	400 mW
ESD Susceptibility (Note 6)	2000V
Operating Temperature Range (Note 5)
LM134	−55ÊC to +125ÊC

LM234/LM234-3/LM234-6	−25ÊC to +100ÊC
LM334	0ÊC to +70ÊC
Soldering Information
TO-92 Package (10 sec.)	260ÊC
TO-46 Package (10 sec.)	300ÊC
SO Package
Vapor Phase (60 sec.)	215ÊC
Infrared (15 sec.)	220ÊC

See AN-450 ªSurface Mounting Methods and Their Effect on Product Reliabilityº (Appendix D) for other methods of soldering surface mount devices.

Electrical Characteristics (Note 2)

Parameter	Conditions		LM134/LM234					LM334		Units
		Min		Typ		Max	Min	Typ	Max
Set Current Error, V+=2.5V,	10µA ≤ ISET ≤ 1mA					3			6	%
(Note 3)	1mA < ISET ≤ 5mA					5			8	%
	2µA ≤ ISET < 10µA					8			12	%
Ratio of Set Current to	100µA ≤ ISET ≤ 1mA	14		18		23	14	18	26
Bias Current	1mA ≤ ISET ≤ 5mA			14				14
	2 µA≤ISET≤100 µA			18		23		18	26
Minimum Operating Voltage	2µA ≤ ISET ≤ 100µA			0.8				0.8		V
	100µA < ISET ≤			0.9				0.9		V
	1mA
	1mA < ISET ≤ 5mA			1.0				1.0		V
Average Change in Set Current	2µA ≤ ISET ≤ 1mA
with Input Voltage	1.5 ≤ V+ ≤ 5V			0.02		0.05		0.02	0.1	%/V
	5V ≤ V+ ≤ 40V			0.01		0.03		0.01	0.05	%/V
	1mA < ISET ≤ 5mA
	1.5V ≤ V ≤ 5V			0.03				0.03		%/V
	5V ≤ V ≤ 40V			0.02				0.02		%/V
Temperature Dependence of	25µA ≤ ISET ≤ 1mA	0.96T		T		1.04T	0.96T	T	1.04T
Set Current (Note 4)
Effective Shunt Capacitance				15				15		pF

Note 1: .ªAbsolute Maximum Ratingsº indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the deviceis functional, but do not guarantee specific performance limits.

Note 2: Unless otherwise specified, tests are performed at Tj = 25ÊC with pulse testing so that junction temperature does not change during test

Note 3: Set current is the current flowing into the V+ pin. For the Basic 2-Terminal Current Source circuit shown on the first page of this data sheet. ISET is determined by the following formula: ISET = 67.7 mV/RSET (@ 25ÊC). Set current error is expressed as a percent deviation from this amount. ISET increases at 0.336%/ÊC @ Tj = 25ÊC (227 µV/ÊC).

Note 4: ISET is directly proportional to absolute temperature (ÊK). ISET at any temperature can be calculated from: ISET = Io (T/To) where Io is ISET measured at To (ÊK).

Note 5: For elevated temperature operation, TJ max is:

LM134	150ÊC
LM234	125ÊC
LM334	100ÊC
Thermal Resistance	TO-92	TO-46	SO-8
θja (Junction to Ambient)	180ÊC/W (0.4" leads)	440ÊC/W	165ÊC/W
	160ÊC/W (0.125" leads)
θjc (Junction to Case)	N/A	32ÊC/W	80ÊC/W

Note 6: Human body model, 100pF discharged through a 1.5kΩ resistor.

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Electrical Characteristics (Note 2)

Parameter	Conditions		LM234-3			LM234-6		Units
		Min	Typ	Max	Min	Typ	Max
Set Current Error, V+=2.5V,	100µA ≤ ISET ≤			±1			±2	%
	1mA
(Note 3)	TJ = 25Ê
Equivalent Temperature Error				±3			±6	ÊC
Ratio of Set Current to	100µA ≤ ISET ≤	14	18	26	14	18	26
	1mA
Bias Current
Minimum Operating Voltage	100µA ISET ≤ 1mA		0.9			0.9		V
Average Change in Set Current	100µA ≤ ISET ≤
	1mA
with Input Voltage	1.5 ≤ V+ ≤ 5V		0.02	0.05		0.02	0.01	%/V
	5V ≤ V+ ≤ 30V		0.01	0.03		0.01	0.05	%/V
Temperature Dependence of	100µA ≤ ISET ≤	0.98T	T	1.02T	0.97T	T	1.03T
	1mA
Set Current (Note 4) and
Equivalent Slope Error				±2			±3	%
Effective Shunt Capacitance			15			15		pF

LM134/LM234/LM334

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LM134/LM234/LM334

Typical Performance Characteristics

Output Impedance	Maximum Slew Rate
	Linear Operation

	DS005697-30
	DS005697-31
Start-Up	Transient Response

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Voltage Across RSET (VR)

Current Noise

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Typical Performance Characteristics (Continued)

Turn-On Voltage

Ratio of ISET to IBIAS

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Application Hints

The LM134 has been designed for ease of application, but a general discussion of design features is presented here to familiarize the designer with device characteristics which may not be immediately obvious. These include the effects of slewing, power dissipation, capacitance, noise, and contact resistance.

CALCULATING RSET

The total current through the LM134 (ISET) is the sum of the current going through the SET resistor (IR) and the LM134's

bias current (IBIAS), as shown in Figure 1.

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FIGURE 1. Basic Current Source

A graph showing the ratio of these two currents is supplied under Ratio of ISET to IBIAS in the Typical Performance Characteristics section. The current flowing through RSET is determined by VR, which is approximately 214µV/ÊK (64 mV/ 298ÊK 214µV/ÊK).

Since (for a given set current) IBIAS is simply a percentage of ISET, the equation can be rewritten

where n is the ratio of ISET to IBIAS as specified in the Electrical Characteristics Section and shown in the graph. Since

n is typically 18 for 2µA ≤ ISET ≤ 1mA, the equation can be further simplified to

for most set currents.

SLEW RATE

At slew rates above a given threshold (see curve), the LM134 may exhibit non-linear current shifts. The slewing rate at which this occurs is directly proportional to ISET. At ISET = 10µA, maximum dV/dt is 0.01V/µs; at I SET = 1mA, the limit is 1V/µs. Slew rates above the limit do not harm the LM134, or cause large currents to flow.

THERMAL EFFECTS

Internal heating can have a significant effect on current regulation for ISET greater than 100µA. For example, each 1V increase across the LM134 at ISET = 1 mA will increase junction temperature by ≈0.4ÊC in still air. Output current (ISET) has a temperature coefficient of ≈0.33%/ÊC, so the change in current due to temperature rise will be (0.4) (0.33) = 0.132%. This is a 10:1 degradation in regulation compared to true electrical effects. Thermal effects, therefore, must be taken into account when DC regulation is critical and ISET exceeds 100µA. Heat sinking of the TO-46 package or the TO-92 leads can reduce this effect by more than 3:1.

SHUNT CAPACITANCE

In certain applications, the 15 pF shunt capacitance of the LM134 may have to be reduced, either because of loading problems or because it limits the AC output impedance of the current source. This can be easily accomplished by buffering the LM134 with an FET as shown in the applications. This can reduce capacitance to less than 3 pF and improve regulation by at least an order of magnitude. DC characteristics (with the exception of minimum input voltage), are not affected.

LM134/LM234/LM334

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