Sipex Corporation SPX2945T5, SPX2945T5-3.3, SPX2945T5-5.0, SPX2945U3, SPX2945U3-3.3 Datasheet

	SPX2945/46/47
	500mA Low Drop Out Voltage Regulator
	with Shutdown
	(PRELIMINARY INFORMATION)
FEATURES	APPLICATIONS
• Output Accuracy 3.3V, 5.0V, @ 500mA Output	• Battery Powered Systems
• Very Low Quiescent Current	• Cordless Telephones
• Low Dropout Voltage	• Radio Control Systems
• Extremely Tight Load And Line Regulation	• Portable/Palm Top/Notebook Computers
• Very Low Temperature Coefficient	• Portable Consumer Equipment
• Current & Thermal Limiting	• Portable Instrumentation
• Error Flag Warns Of Output Dropout	• Automotive Electronics
• Logic-Controlled Electronic Shutdown	• SMPS Post-Regulator
• Output Programmable From 1.24V to 29V	• Voltage Reference

PRODUCT DESCRIPTION

The SPX2945/46/47 is a low power voltage regulator. This device is an excellent choice for use in battery-powered applications such as cordless telephones, radio control systems, and portable computers. The SPX2945/46/47 features very low quiescent current (100 A Typ.) and very low dropout voltage. This includes a tight initial tolerance of 1% max and very low output temperature coefficient, making the SPX2945/46/47 useful as a low-power voltage reference.

The error flag output feature is used as power-on reset for warning of a low output voltage, due to a falling voltage input of batteries. Another feature is the logic-compatible shutdown input which enables the regulator to be switched on and off. The SPX2945/46/47 is offered in 3-pin and 5-pin TO-220 package, SO-8 (same pin out as SPX2951), SOT-223, and surface mount TO-263 packages.

The regulator output voltage (of the 8-pin SO-8 and 5-pin TO-220 & TO-263) may be pin-strapped for a 3.3V and 5.0V or programmed from 1.24V to 29V with an external pair of resistors. Look for SPX2951 for 150mA, SPX2954 for 250mA and SPX2955 for 350mA applications.

PIN CONNECTIONS

	TO-263-5 (T)
						Five Lead Package Pin Functions:
						SPX2946		SPX2947
	SPX2946/47					1) ERROR		1)	ERROR
						2) VIN		2) SHUTDOWN
	1	2	3	4	5	3)	GND	3)	GND
						4)	VOUT	4)	VIN
						5)	SHUTDOWN 5)		VOUT

TO-220-5 (U)												TO-220-3 (U)									TO-263-3 (T)								TO-252 (R)								8-Pin Surface Mount (S)					SOT-223 (M3)
																																				VOUT
																																						1	8		VIN
																						SPX2945								SPX2945								2	7				SPX2945
SPX2946/47												SPX2945																	1			2 3				SENSE					FEEDBACK	1		2			3
																					1		2			3													SPX2945
1			2		3		4	5				1		2		3																				SHUTDOWN		3	6		5V/ 3.3V TAP
																																				GND		4	5		ERROR	VIN		GND VOUT
																													VIN			GND VOUT
																					VIN		GND			VOUT

		VIN GND VOUT
Top View	Front View	Front View	Top View	Top View	Top View	Top View

Rev. 10/25/00

SPX2945/46/47

ABSOLUTE MAXIMUM RATINGS

Power Dissipation..........................................	Internally Limited
Lead Temp. (Soldering, 5 Seconds) ................................	260°C
Storage Temperature Range ..............................	-65° to +150°C
Operating Junction Temperature Range (Note 9)
SPX2945/46/47......................................	-40C° to +125°C
ESD Rating ................................................................	2KV Min
Operating Supply Voltage .........................................................

Input Supply Voltage .....................................	+3.0V to +60V
Feedback Input Voltage ..................................	-1.5V to +30V
Shutdown Input Voltage..................................	-0.3V to +30V
Error Comparator Output ................................	-0.3V to +30V
ESD Rating ............................................................	2KV Min

ELECTRICAL CHARACTERISTICS at VIN =VOUT±15V,TA=25°C, unless otherwise specified. Boldface applies over the full operating temperature range.

PARAMETER	CONDITIONS		SPX2945/46		UNITS
	(Note 2)	Typ.	Min	Max
3.3V Version
Output Voltage	1mA ≤IL ≤ 500mA	3.3	3.267	3.333	V
		3.3	3.217	3.382
5.0V Version
Output Voltage	1mA ≤IL ≤ 500mA	5.0	4.950	5.050	V
		5.0	4.880	5.120
All Voltage Options			SPX2945/46/47
Output Voltage		20		100	ppm/°C
Temperature Coefficient	(Note 1)
Line Regulation ( Note 3)	6V ≤ VIN ≤30V (Note 4)	0.03		0.1	%max
				0.40
Load Regulation ( Note 3 )	IL = 1 to 500mA	0.04		0.20	%max
	IL = 0.1 to 1mA			0.30
Dropout Voltage	IL = 1mA	60		100	mV
( Note 5 )				150
	IL = 500mA	350		400
				500
Ground Current	IL = 1mA	50		100	A
				150
	IL = 150mA	0.5		1	mA
				2
	IL = 300mA	4		8
				10
	IL = 500mA	5		10
				15
Current Limit	VOUT = 0			700	mA
				800
Thermal Regulation		0.05		0.2	%/w
Output Noise, 10Hz to 100kHz	CL = 2.2 F	400			V Vrms
IL = 100mA	CL = 33 F	260
Adjustable Versions only		Typ	SPX2945/47
Reference Voltage		1.235	1.210	1.260	V
			1.200	1.270
Reference Voltage	Over Temperature (Note 6)		1.185	1.285	V
Feedback Pin Bias Current		20		40	nA
				60
Reference Voltage Temperature	(Note 7)	50			ppm/°C
Coefficient
Feedback Pin Bias Current		0.1			nA/°C
Temperature Coefficient

Rev. 10/25/00

							SPX2945/46/47
(Continued)
PARAMETER	CONDITIONS					SPX2945/46/47		UNITS
	(Note 2)			Typ.		Min	Max	A
Output Leakage Current	V0H = 30V			0.01			1.00
							2.00
Output Low Voltage	VIN = 4.5V			150			250	mV
	I0L = 400 A						400
Upper Threshold Voltage	(Note 8)			60		40		mV
Lower Threshold Voltage	(Note 8)			75		25	95	mV
Hysteresis	(Note 8)			15			140	mV
Input logic Voltage	Low (Regulator ON)						0.7	V
	High (Regulator OFF)			1.3		2.0	50	A
Shut down Pin Input Current	VS = 2.4V			30
							100
	VS = 30V			450			600
Regulator Output Current in Shutdown				3		10	750	A
						20
Note 1: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.
Note 2: Unless otherwise specified all limits are guaranteed for Tj = 25°C, VIN = 6V, IL = 100 A and CL = 1 F. Additional conditions for the 8-pin versions are
feedback tied to 5V tap and output tied to output sense (VOUT = 5V) and VSHUTDOWN ≤ 0.8V.
Note 3: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are
covered under the specification for thermal regulation.
Note 4: Line regulation for the SPX2945/46/47 is tested at 150°C for IL = 1 mA. For IL = 100 A and TJ = 125°C, line regulation is guaranteed by design to 0.2%. See
typical performance characteristics for line regulation versus temperature and load current.
Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential at
very low values of programmed output voltage, the minimum input supply voltage of 2V ( 2.3V over temperature) must be taken into account.
Note 6: VREF ≤VOUT ≤ (Vin - 1V), 2.3 ≤Vin≤30V, 100 A≤IL≤ 250 mA, TJ ≤ TJMAX.
Note 7: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference voltage measured at 6V input. To
express these thresholds in terms of output voltage change, multiply by the error amplifier gain = VOUT/VREF = (R1 + R2)/R2. For example, at a programmed output
voltage of 5V, the Error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 = 384 mV. Thresholds remain constant as a percent of VOUT as
VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 8: VSHUTDOWN ≥ 2V, VIN ≤ 30V, VOUT =0, Feedback pin tied to 5V Tap.
Note 9: The junction -to-ambient thermal resistance of the TO-92 package is 180°C/ W with 0.4” leads and 160°C/ W with 0.25” leads to a PC board.
The thermal resistance of the 8-Pin DIP package is 105°C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient thermal resistance for the
SOIC (S) package is 160°C/W.
	UNREGULATED DC
	7	8			1		5V @ 500mA
							MAX
	+
	FEEDBACK	INPUT		OUTPUT
						2
						SENSE
		+		180k Ω ..
						6
	3	_	ERROR
FROM			AMPLIFIER
						5V TAP	330k Ω ..
CMOS OR
TTL	SHUTDOWN						+
				60k	Ω ..	5
	+
		+				______	1µF
	60 mV
		_	ERROR DETECTION			ERROR
							TO CMOS OR
	+ 1.23V		COMPARATOR
							TTL
						4
	REFERENCE					GROUND
	SPX2945/46/47 Block Diagram

Rev. 10/25/00

SPX2945/46/47

APPLICATION HINTS

EXTERNAL CAPACITORS

The stability of the SPX2945/46/47 requires a 2.2µF or greater capacitor between output and ground. Oscillation could occur without this capacitor. Most types of tantalum or aluminum electrolytic works fine here. For operations of below -25°C solid tantalum is recommended since the many aluminum types have electrolytes the freeze at about -30°C. The ESR of about 5Ω or less and resonant frequency above 500kHz are the most important parameters in the value of the capacitor. The capacitor value can be increased without limit.

At lower values of output current, less output capacitance is required for stability. For the currents below 10mA the value of the capacitor can be reduced to 0.5µF and 0.15µF for 1mA. More output capacitance needed for the 8-pin version at voltages below 5V since it runs the error amplifier at lower gain. At worst case 5µF or greater must be used for the condition of 250mA load at 1.23V output.

The SPX2945/46/47, unlike other low dropout regulators will remain stable and in regulation with no load in addition to the internal voltage divider. This feature is especially important in application like CMOS RAM keep-alive. When setting the output voltage of the SPX2945/46/47, a minimum load of 10mA is recommended.

If there is more than 10 inches of wire between the input and the AC filter capacitor or if a battery is used as the input then a 0.1µF tantalum or aluminum electrolytic capacitor should be placed from the input to the ground.

Instability can occur if there is stray capacitance to the SPX2945/46/47 feedback terminal (pin 7). This could cause more problems when using a higher value of external resistors to set the output voltage.

4 .7 5 V

O U T PU T

V O L T A G E

_ _ _ _ _ _ _

E R R O R *

	+5 .0 V	+
IN P U T	+1 .3 V	+
V O L T A G E

* S ee A pp lication In fo . _ _ __ _ __

F igure 1 . E R R O R O u tp u t T im in g

This problem can be fixed by adding a 100pF capacitor between output and feedback and increasing the output capacitor to at least 3.3µF.

ERROR DETECTION COMPARATOR OUTPUT

The Comparator produces a logic low output whenever the SPX2945/46/47 output falls out of regulation by more than around 5%. This is around 60mV offset divided by the 1.235 reference voltage. This trip level remains 5% below normal regardless of the programmed output voltage of the regulator. Figure 1 shows the timing diagram depicting the ERROR signal and the regulator output voltage as the SPX2945/46/47 input is ramped up and down. The ERROR signal becomes low at around 1.3V input, and goes high around 5V input (input voltage at which Vout = 4.75). Since the SPX2945/46/47’s dropout voltage is load dependent, the input voltage trip point (around 5V) will vary with the load current. The output voltage trip point (approx. 4.75V) does not vary with load.

The error comparator has an open-collector output, which requires an external pull-up resistor. Depending on the system requirements the resistor may be returned to 5V output or other supply voltage. In determining the value of this resistor, note that the output is rated to sink 400µA, this value adds to battery drain in a low battery condition. Suggested values range from 100K to 1MΩ. If the output is unused this resistor is not required.

PROGRAMMING THE OUTPUT VOLTAGE OF SPX2945/46/47

The SPX2945/46/47 may be pin-strapped for 5V using its internal voltage divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback) to Pin 6 (5V Tap).

		+VIN
100K		8
ERROR	5 ______	+VIN		1.2 to 29V
OUTPUT	ERROR	1
		VOUT
	SPX2945
SHUTDOWN			R1	+
	3			10uF
INPUT	SD			.01uF
	GND	FB
	4	7
		1.23V
		VREF	R2

Figure 2. Adjustable Regulator

Rev. 10/25/00

SPX2945/46/47

Also, it may be programmed for any output voltage between its 1.235V reference and its 30V maximum rating. As seen in Figure 2, an external pair of resistors is required.

Refer to the below equation for the programming of the output voltage::

VOUT = VREF × ( 1 + R1/ R2 )+ IFBR1

The VREF is 1.235 and IFB is the feedback bias current, nominally -20nA. The minimum recommended load current of 1 µA forces an upper limit of 1.2 MΩ on value of R2. If no load is presented

the IFB produces an error of typically 2% in VOUT, which may be eliminated at room temperature by trimming R1. To improve the

accuracy choose the value of R2 = 100k this reduces the error by 0.17% and increases the resistor program current by 12µA. Since the SPX2945/46/47 typically draws 60 µA at no load with Pin 2 open-circuited this is a small price to pay

REDUCING OUTPUT NOISE

It may be an advantage to reduce the AC noise present at the output. One way is to reduce the regulator bandwidth by increasing the size of the output capacitor. This is the only way that noise can be reduced on the 3 lead SPX2945/46/47 but is relatively inefficient, as increasing the capacitor from 1µF to 220µF only decreases the noise from 430µV to 160µV Vrms for a 100kHz bandwidth at 5V output.

Noise could also be reduced fourfold by a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick

CBYPASS 1 / 2πR1 × 200 Hz

or choose 0.01µF. When doing this, the output capacitor must be increased to 3.3µF to maintain stability. These changes reduce the output noise from 430µV to 100µV Vrms for a 100kHz bandwidth at 5V output. With the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages.

HEAT SINK REQUIREMENTS
Depending on the maximum ambient temperature and maximum
power dissipation a heat sink may be required with the
SPX2945/46/47. The junction temperature range has to be within
the range specified under Absolute Maximum Ratings under all
possible operating conditions. To find out if a heat sink is
required, the maximum power dissipation of the device needs to
be calculated. This is the maximum specific AC voltage that
must be taken into consideration at input. Figure 3 shows the
condition and power dissipation which should be calculated with		Iin						5V
the following formula:	Vin					IN	OUT
PTOTAL = (VIN - 5) IL + (VIN)IG							SPX2945
Next step is to calculate the temperature rise TR (max). TJ (max)			+					+
								2.2 uF
maximum allowable junction temperature, TA (max) maximum							GND
ambient temperature :

IL

LOAD

TR (max) = TJ (max) - TA (max)			IG
		IIN = IL + IG
Junction to ambient thermal resistance θ(j-A) can be calculated
after determining of PTOTAL & TR (max):		Figure3 5V Regulator Circuit
θ(J-A) = TR (max)/P(max)
If the θ(J-A) is 60°C/W or higher, the device could be operated
without a heat sink. If the value is below 60°C/W then the heat
sink is required and the thermal resistance of the heat sink can be
calculated by the following formula, θ(J-C) junction to case, θ(C-H)
case to heat sink, θ(H-A)	heat sink to ambient:
θ(J-A)	= θ(J-C) + θ(C-H) + θ(H-A)

Rev. 10/25/00