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SPX3940/41/42
1A Low Drop Out Voltage Regulator with Shutdown
(PRELIMINARY INFORMATION)
FEATURES
* Output Accuracy 3.3V, @ 1A Output * Very Low Quiescent Current * Low Dropout Voltage * Extremely Tight Load And Line Regulation * Very Low Temperature Coefficient * Current & Thermal Limiting * Error Flag Warns Of Output Dropout
APPLICATIONS
* Battery Powered Systems * Cordless Telephones * Radio Control Systems * Portable/Palm Top/Notebook Computers * Portable Consumer Equipment * Portable Instrumentation * Automotive Electronics * SMPS Post-Regulator * Voltage Reference
PRODUCT DESCRIPTION
The SPX3940/41/42 is a low power voltage regulator. This device is an excellent choice for battery-powered applications such as cordless telephones, radio control systems and portable computers. The SPX3940/41/42 features very low quiescent current (100A Typ.) and very low dropout voltage. This includes a tight initial tolerance of 1% max and 2% max., and very low output temperature coefficient, making the SPX3940/41/42 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 SPX3940/41/42 is offered in 3-pin and 5-pin TO-220 package 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 or programmed from 1.24V to 29V with an external pair of resistors.
PIN CONNECTIONS
TO-263-5 Package TO-220-5 Package SOT-223 Package
TO-220 Package
VOUT
SPX3941/42 Five Lead Package Pin Functions: SPX3941 SPX3942 1) ERROR 2) INPUT 3) GND 12345 4) OUTPUT 5) SHUTDOWN
ADJUST SHUTDOWN GND INPUT OUTPUT
SPX3940
SPX3941/42
1 2 3
SPX3940
GND/ ADJ V IN
V GND/ VOUT IN
ADJ
Front View
Front View TO-252 Package
TO-263Package
12 345 SPX3940
2 1
Top View
ADJ/GND VIN
SPX3940
Top View
3
VOUT
3 VOUT 2 GND/ ADJ 1 V IN
Front View
Front View
Rev. 12/19/00
SPX3940/41/42
ABSOLUTE MAXIMUM RATINGS
Power Dissipation..........................................Internally Limited Lead Temp. (Soldering, 5 Seconds) ................................ 260C Storage Temperature Range .............................. -65 to +150C Operating Junction Temperature Range (Note 9) SPX3940/41/42...................................... -40C to +125C Input Supply Voltage ................................................... +7.5V 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 VS=15V,TA=25C, unless otherwise specified. Boldface applies over the full
operating temperature range.
PARAMETER 3.3V Version Output Voltage
-40C TJ +125C
CONDITIONS
Typ.
(Note 2)
3.3 3.3
SPX3940A Min Max 3.267 3.217 3.333 3.382
SPX3940/41 Min Max 3.234 3.185 3.366 3.415
UNITS
V
1mA IL 1A All Voltage Options Output Voltage Temperature Coefficient Line Regulation ( Note 3) Load Regulation ( Note 3 ) Output Noise Voltage Ground Current
20 (Note 1) 6V VIN 30V (Note 4) IL = 50mA to 1mA BV = 10Hz - 100kHz IL = 5mA 4.5V100 40 50 80
150 60 50 80
ppm/C mV mV V(rms)
15 20 200 250 1.2 0.2 0.8 1.0 150 200 1.2
15 20 200 250
mA
Current Limit Thermal Regulation Dropout Voltage (Note 5)
110 1.7 0.05 0.5 110 Typ 1.235
A %/w V
IL = 1A IL = 100mA
Adjustable Versions only
Reference Voltage Reference Voltage Feedback Pin Bias Current Reference Voltage Temperature Coefficient Feedback Pin Bias Current Temperature Coefficient (Note 7) Over Temperature (Note 6)
0.2 0.8 1.0 150 200 SPX3940/42 1.200 1.270 1.98 1.272 1.185 1.285 60 80
V V nA ppm/C nA/C
20 50 0.1
Rev. 12/19/00
SPX3940/41/42
(Continued) PARAMETER
Output Leakage Current Output Low Voltage Upper Threshold Voltage Lower Threshold Voltage Hysteresis Input logic Voltage Shut down Pin Input Current
CONDITIONS
(Note 2)
Typ. Min 0.01 150 60 75 15 1.3 30 450 3 2.0 40 25
SPX3940/42 Max 1.00 2.00 250 400
UNITS A mV mV 95 140 mV mV V 0.7 90 150 800 1000 15 25 A
V0H = 30V VIN = 4.5V I0L = 400A (Note 8) (Note 8) (Note 8) Low (Regulator ON) High (Regulator OFF) VS = 2.4V VS = 30V
Regulator Output Current in Shutdown
A
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 = 25C, VIN = 6V, IL = 100A and CL = 1F. 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 SPX3940/41/42 is tested at 150C for IL = 1 mA. For IL = 100A and TJ = 125C, 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 Vin30V, 100AIL 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 180C/ W with 0.4" leads and 160C/ W with 0.25" leads to a PC board. The thermal resistance of the 8-Pin DIP package is 105C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient thermal resistance for the SOIC (S) package is 160C/W.
Rev. 12/19/00
SPX3940/41/42
APPLICATION HINTS
EXTERNAL CAPACITORS
The stability of the SPX3940/41/42 requires a 2.2F 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 -25C solid tantalum is recommended since the many aluminum types have electrolytes the freeze at about -30C. The ESR of about 5 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 0.5F and 0.15F for 1A. 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 5F or greater must be used for the condition of 250mA load at 1.23V output. The SPX3940/41/42, 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 SPX3940/41/42, 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 0.1F tantalum or aluminum electrolytic capacitor should be placed from the input to the ground. Instability can occur if there is stray capacitance to the SPX3940/41/42 feedback terminal (pin 7). This could cause more problems when using a higher value of external resistors to set the output voltage. This problem can be fixed by adding a 100pF capacitor between output and feedback and increasing the output capacitor to at least 3.3F.
ERROR DETECTION COMPARATOR OUTPUT
The Comparator produces a logic low output whenever the SPX3940/41/42 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 SPX3940/41/42 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 SPX3940/41/42'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 400A, this value adds to battery drain in a low battery condition. Suggested values range from 100K to 1M. If the output is unused this resistor is not required.
PROGRAMMING THE OUTPUT VOLTAGE OF SPX3940/41/42
The SPX3940/41/42 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).
4 .7 5 V O U T PU T V OL TA GE _______ ERRO R*
+5 .0 V
IN P U T V OL TA GE
+1 .3 V
+ +
* S e e A p p lica tio n In fo .
_______ F ig u r e 1 . E R R O R O u tp u t T im in g
Rev. 12/19/00
SPX3940/41/42
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 x ( 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 A forces an upper limit of 1.2 M 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 12A. Since the LP2951 typically draws 60 A at no load with Pin 2 opencircuited 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 SPX3940/41/42 but is relatively inefficient, as increasing the capacitor from 1F to 220F only decreases the noise from 430V to 160V 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 / 2R1 x 200 Hz or choose 0.01F. When doing this, the output capacitor must be increased to 3.3F to maintain stability. These changes reduce the output noise from 430V to 100V 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 SPX3940/41/42. 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 the following formula: PTOTAL = (VIN - 5) IL + (VIN)IG Next step is to calculate the temperature rise TR (max). TJ (max) maximum allowable junction temperature, TA (max) maximum ambient temperature : TR (max) = TJ (max) - TA (max) Junction to ambient thermal resistance (j-A) can be calculated after determining of PTOTAL & TR (max): (J-A) = TR (max)/P(max) If the (J-A) is 60C/W or higher, the device could be operated without a heat sink. If the value is below 60C/W then the heat sink is required and the thermal resistance of the heat sink can be calculated by the following formula, (J-C) junction to case, (C-H) case to heat sink, (H-A) heat sink to ambient: (J-A) = (J-C) + (C-H) + (H-A)
IIN = IL + IG
+
VIN
IIN IN OUT
3.3V IL
SPX3940
+
LOAD
2.2 uF
GND
IG
Figure 3. 3.3V Regulator Circuit
Rev. 12/19/00
SPX3940/41/42
TYPICAL APPLICATIONS
+VIN
+VIN VOUT *V
OUT
= 3.3V
SPX3940
+
10uF GND
4
SPX3940 FIXED +3.3V REGULATOR
Rev. 12/19/00
SPX3940/41/42
ORDERING INFORMATION Ordering No.
SPX3940AM3 SPX3940AM3-3.3 SPX3940AM3-5.0 SPX3940M3 SPX3940M3-3.3 SPX3940M3-5.0 SPX3940AR SPX3940AR-3.3 SPX3940AR-5.0 SPX3940R SPX3940R-3.3 SPX3940R-5.0 SPX3940AU SPX3940AU-3.3 SPX3940AU-5.0 SPX3940U SPX3940U-3.3 SPX3940U-5.0 SPX3940AT SPX5940AT-3.3 SPX3940AT-5.0 SPX3940T SPX3940T-3.3 SPX3940T-5.0 SPX3941R-3.3 SPX3941R-5.0 SPX3941U-3.3 SPX3941U-5.0 SPX3941T-3.3 SPX3941T-5.0 SPX3942R SPX3942U SPX3942T
Precision Output Voltage
1% 1% 1% 2% 2% 2% 1% 1% 1% 2% 2% 2% 1% 1% 1% 2% 2% 2% 1% 1% 1% 2% 2% 2% 2% 2% 2% 2% 2% 2% 2% 2% 2% Adj 3.3V 5.0V Adj 3.3V 5.0V Adj 3.3V 5.0V Adj 3.3V 5.0V Adj 3.3V 5.0V Adj 3.3V 5.0V Adj 3.3V 5.0V Adj 3.3V 5.0V 3.3V 5.0V 3.3V 5.0V 3.3V 5.0V Adj Adj Adj
Packages
3 Lead SOT-223 3 Lead SOT-223 3 Lead SOT-223 3 Lead SOT-223 3 Lead SOT-223 3 Lead SOT-223 5 Lead TO-252 3 Lead TO-252 3 Lead TO-252 5 Lead TO-252 3 Lead TO-252 3 Lead TO-252 5 Lead TO-220 3 Lead TO-220 3 Lead TO-220 5 Lead TO-220 3 Lead TO-220 3 Lead TO-220 5 Lead TO-263 3 Lead TO-263 3 Lead TO-263 5 Lead TO-263 3 Lead TO-263 3 Lead TO-263 3 Lead TO-252 3 Lead TO-252 3 Lead TO-220 3 Lead TO-220 3 Lead TO-263 3 Lead TO-263 5 Lead TO-252 3 Lead TO-220 3 Lead TO-263
Corporation
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation
Headquarters and Main Offices: 22 Linnell Circle Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001 e-mail: sales@sipex.com 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 935-7600 FAX: (408) 934-7500
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others.
Rev. 12/19/00

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