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LP2985 Micropower SOT, 150 mA Low-Noise Ultra Low-Dropout Regulator
March 1999
LP2985 Micropower SOT, 150 mA Low-Noise Ultra Low-Dropout Regulator Designed for Use with Very Low ESR Output Capacitors
General Description
The LP2985 is a 150 mA, fixed-output voltage regulator designed to provide ultra low-dropout and low noise in battery powered applications. Using an optimized VIPTM (Vertically Integrated PNP) process, the LP2985 delivers unequalled performance in all specifications critical to battery-powered designs: Dropout Voltage: Typically 300 mV @ 150 mA load, and 7 mV @ 1 mA load. Ground Pin Current: Typically 850 A @ 150 mA load, and 75 A @ 1 mA load. Enhanced Stability: The LP2985 is stable with output capacitor ESR as low as 5 m, which allows the use of ceramic capacitors on the output. Sleep Mode: Less than 1 A quiescent current when ON/OFF pin is pulled low. Smallest Possible Size: SOT-23 package uses absolute minimum board space. Precision Output: 1% tolerance output voltages available (A grade). Low Noise: By adding a 10 nF bypass capacitor, output noise can be reduced to 30 V (typical). Multiple voltage options, from 2.8V to 5.0V, are available as standard products. Consult factory for custom voltages.
Features
n n n n n n n n n n n n n n Ultra low dropout voltage Guaranteed 150 mA output current Smallest possible size (SOT-23 Package) Requires minimum external components Stable with low-ESR output capacitor <1 A quiescent current when shut down Low ground pin current at all loads Output voltage accuracy 1% (A Grade) High peak current capability Wide supply voltage range (16V max) Low ZOUT: 0.3 typical (10 Hz to 1 MHz) Overtemperature/overcurrent protection -40C to +125C junction temperature range Custom voltages available
Applications
n n n n Cellular Phone Palmtop/Laptop Computer Personal Digital Assistant (PDA) Camcorder, Personal Stereo, Camera
Block Diagram
DS100140-1
VIPTM is a trademark of National Semiconductor Corporation.
(c) 1999 National Semiconductor Corporation
DS100140
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Basic Application Circuit
DS100140-2
*ON/OFF input must be actively terminated. Tie to VIN if this function is not to be used. **Minimum capacitance is shown to ensure stability (may be increased without limit). Ceramic capacitor required for output (see Application Hints). ***Reduces output noise (may be omitted if application is not noise critical). Use ceramic or film type with very low leakage current (see Application Hints).
Connection Diagram
DS100140-3
See NS Package Number MA05B
Ordering Information
TABLE 1. Package Marking and Ordering Information Output Voltage (V) 2.8 2.8 2.8 2.8 3.0 3.0 3.0 3.0 3.1 3.1 3.1 3.1 3.2 3.2 Package Marking L0KA L0KA L0KB L0KB L0OA L0OA L0OB L0OB L0PA L0PA L0PB L0PB L0QA L0QA
Grade A A STD STD A A STD STD A A STD STD A A
Order Information LP2985AIM5X-2.8 LP2985AIM5-2.8 LP2985IM5X-2.8 LP2985IM5-2.8 LP2985AIM5X-3.0 LP2985AIM5-3.0 LP2985IM5X-3.0 LP2985IM5-3.0 LP2985AIM5X-3.1 LP2985AIM5-3.1 LP2985IM5X-3.1 LP2985IM5-3.1 LP2985AIM5X-3.2 LP2985AIM5-3.2
Supplied as: 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel
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Ordering Information
Output Voltage (V) 3.2 3.2 3.3 3.3 3.3 3.3 3.5 3.5 3.5 3.5 3.6 3.6 3.6 3.6 4.0 4.0 4.0 4.0 5.0 5.0 5.0 5.0
(Continued)
TABLE 1. Package Marking and Ordering Information (Continued) Grade STD STD A A STD STD A A STD STD A A STD STD A A STD STD A A STD STD Order Information LP2985IM5X-3.2 LP2985IM5-3.2 LP2985AIM5X-3.3 LP2985AIM5-3.3 LP2985IM5X-3.3 LP2985IM5-3.3 LP2985AIM5X-3.5 LP2985AIM5-3.5 LP2985IM5X-3.5 LP2985IM5-3.5 LP2985AIM5X-3.6 LP2985AIM5-3.6 LP2985IM5X-3.6 LP2985IM5-3.6 LP2985AIM5X-4.0 LP2985AIM5-4.0 LP2985IM5X-4.0 LP2985IM5-4.0 LP2985AIM5X-5.0 LP2985AIM5-5.0 LP2985IM5X-5.0 LP2985IM5-5.0 Package Marking L0QB L0QB L0RA L0RA L0RB L0RB LAIA LAIA LAIB LAIB L0SA L0SA L0SB L0SB L0TA L0TA L0TB L0TB L0UA L0UA L0UB L0UB Supplied as: 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel 3k Units on Tape and Reel 250 Units on Tape and Reel
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Storage Temperature Range Operating Junction Temperature Range Lead Temp. (Soldering, 5 sec.) ESD Rating (Note 2) Power Dissipation (Note 3) -65C to +150C -40C to +125C 260C 2 kV Internally Limited
Input Supply Voltage (Survival) Input Supply Voltage (Operating) Shutdown Input Voltage (Survival) Output Voltage (Survival, (Note 4)) IOUT (Survival) Input-Output Voltage (Survival, (Note 5))
-0.3V to +16V 2.5V to +16V -0.3V to +16V -0.3V to +9V Short Circuit Protected -0.3V to +16V
Electrical Characteristics
Limits in standard typeface are for TJ = 25C. and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VO(NOM) + 1V, IL = 1 mA, CIN = 1 F, COUT = 4.7 F, VON/OFF = 2V. LP2985AI-X.X Symbol VO Parameter Output Voltage Tolerance Conditions IL = 1 mA 1 mA IL 50 mA 1 mA IL 150 mA Output Voltage Line Regulation VIN-VO Dropout Voltage (Note 7) IL = 0 IL = 1 mA IL = 10 mA IL = 50 mA IL = 150 mA IGND Ground Pin Current IL = 0 IL = 1 mA IL = 10 mA IL = 50 mA IL = 150 mA VON/OFF < 0.3V VON/OFF < 0.15V VON/OFF ION/OFF en ON/OFF Input Voltage (Note 8) ON/OFF Input Current Output Noise Voltage (RMS) High = O/P ON Low = O/P OFF VON/OFF = 0 VON/OFF = 5V BW = 300 Hz to 50 kHz, COUT = 10 F CBYPASS = 10 nF 30 V 1 7 40 120 280 65 75 120 350 850 0.01 0.05 1.4 0.55 0.01 5 1.6 0.15 -2 15 VO(NOM)+1V VIN 16V 0.007 Typ (Note 6) Min -1.0 -1.5 -2.5 -2.5 -3.5 Max 1.0 1.5 2.5 2.5 3.5 0.014 0.032 3 5 10 15 60 90 150 225 350 575 95 125 110 170 220 400 600 1000 1500 2500 0.8 2 1.6 0.15 -2 15 LP2985I-X.X (Note 6) Min -1.5 -2.5 -3.5 -3.0 -4.0 Max 1.5 2.5 3.5 3.0 4.0 0.014 0.032 3 5 10 15 60 90 150 225 350 575 95 125 110 170 220 400 600 1000 1500 2500 0.8 2 V A A mV %/V %VNOM Units
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Electrical Characteristics
(Continued)
Limits in standard typeface are for TJ = 25C. and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VO(NOM) + 1V, IL = 1 mA, CIN = 1 F, COUT = 4.7 F, VON/OFF = 2V. LP2985AI-X.X Symbol Parameter Ripple Rejection Conditions f = 1 kHz, CBYPASS = 10 nF COUT = 10 F IO(SC) IO(PK) Short Circuit Current Peak Output Current RL = 0 (Steady State) (Note 9) VOUT Vo(NOM) -5% 45 dB Typ (Note 6) Min Max LP2985I-X.X (Note 6) Min Max Units
400 350
mA mA
Note 1: "Absolute Maximum Ratings" indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its rated operating conditions. Note 2: The ESD rating of pins 3 and 4 is 1 kV. Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, J-A, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperture is calculated using:
Where the value of J-A for the SOT-23 package is 220C/W in a typical PC board mounting. Exceeding the maximum allowable dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Note 4: If used in a dual-supply system where the regulator load is returned to a negative supply, the LP2985 output must be diode-clamped to ground. Note 5: The output PNP structure contains a diode between the VIN to VOUT terminals that is normally reverse-biased. Reversing the polarity from VIN to VOUT will turn on this diode. Note 6: Limits are 100% production tested at 25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. The limits are used to calculate National's Average Outgoing Quality Level (AOQL). Note 7: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential. Note 8: The ON/OFF input must be properly driven to prevent possible misoperation. For details, refer to Application Hints. Note 9: The LP2985 has foldback current limiting which allows a high peak current when VOUT > 0.5V, and then reduces the maximum output current as VOUT is forced to ground (see Typical Performance Characteristics curves).
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Typical Performance Characteristics
VOUT(NOM) +1, TA = 25C, ON/OFF pin is tied to VIN. VOUT vs Temperature
Unless otherwise specified: CIN = 1F, COUT = 4.7F, VIN =
Short-Circuit Current
Short-Circuit Current
DS100140-9 DS100140-8
DS100140-10
Short Circuit Current vs Output Voltage
Ripple Rejection
Ripple Rejection
DS100140-13 DS100140-11
DS100140-14
Ripple Rejection
Ripple Rejection
Ripple Rejection
DS100140-15
DS100140-16
DS100140-17
Ripple Rejection
Ripple Rejection
Ripple Rejection
DS100140-18
DS100140-19
DS100140-23
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Typical Performance Characteristics Unless otherwise specified: CIN = 1F, COUT = 4.7F, VIN = VOUT(NOM) +1, TA = 25C, ON/OFF pin is tied to VIN. (Continued)
Ripple Rejection Output Impedance vs Frequency Output Impedance vs Frequency
DS100140-22
DS100140-20
DS100140-21
Output Noise Density
Output Noise Density
Ground Pin vs Load Current
DS100140-24
DS100140-25
DS100140-26
Dropout Voltage vs Temperature
Dropout Voltage vs Load Current
Input Current vs Pin
DS100140-27
DS100140-28
DS100140-29
GND Pin Current vs Temperature
Instantaneous Short Circuit Current
Load Transient Response
DS100140-32 DS100140-30 DS100140-31
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Typical Performance Characteristics Unless otherwise specified: CIN = 1F, COUT = 4.7F, VIN = VOUT(NOM) +1, TA = 25C, ON/OFF pin is tied to VIN. (Continued)
Load Transient Response Load Transient Response Line Transient Response
DS100140-33
DS100140-34
DS100140-35
Line Transient Response
Line Transient Response
Line Transient Response
DS100140-36
DS100140-37
DS100140-38
Turn-On Time
Turn-On Time
Turn-On Time
DS100140-39
DS100140-40
DS100140-41
Turn-On Time
DS100140-42
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Application Hints
EXTERNAL CAPACITORS Like any low-dropout regulator, the LP2985 requires external capacitors for regulator stability. These capacitors must be correctly selected for good performance. Input Capacitor An input capacitor whose capacitance is 1 F is required between the LP2985 input and ground (the amount of capacitance may be increased without limit). This capacitor must be located a distance of not more than 1 cm from the input pin and returned to a clean analog ground. Any good quality ceramic, tantalum, or film capacitor may be used at the input. Important: Tantalum capacitors can suffer catastrophic failure due to surge current when connected to a low-impedance source of power (like a battery or very large capacitor). If a Tantalum capacitor is used at the input, it must be guaranteed by the manufacturer to have a surge current rating sufficient for the application. There are no requirements for ESR on the input capacitor, but tolerance and temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will be 1 F over the entire operating temperature range. Output Capacitor: The LP2985 is designed specifically to work with ceramic output capacitors, utilizing circuitry which allows the regulator to be stable across the entire range of output current with an output capacitor whose ESR is as low as 5 m. It may also be possible to use Tantalum or film capacitors at the output, but these are not as attractive for reasons of size and cost (see next section Capacitor Characteristics). The output capacitor must meet the requirement for minimum amount of capacitance and also have an ESR (equivalent series resistance) value which is within the stable range. Curves are provided which show the stable ESR range as a function of load current (see ESR graph below).
operating temperature range. It should be noted that ceramic capacitors can exhibit large changes in capacitance with temperature (see next section, Capacitor Characteristics). The output capacitor must be located not more than 1 cm from the output pin and returned to a clean analog ground. Noise Bypass Capacitor: Connecting a 10 nF capacitor to the Bypass pin significantly reduces noise on the regulator output. It should be noted that the capacitor is connected directly to a high-impedance circuit in the bandgap reference. Because this circuit has only a few microamperes flowing in it, any significant loading on this node will cause a change in the regulated output voltage. For this reason, DC leakage current through the noise bypass capacitor must never exceed 100 nA, and should be kept as low as possible for best output voltage accuracy. The types of capacitors best suited for the noise bypass capacitor are ceramic and film. High-quality ceramic capacitors with either NPO or COG dielectric typically have very low leakage. 10 nF polypropolene and polycarbonate film capacitors are available in small surface-mount packages and typically have extremely low leakage current. CAPACITOR CHARACTERISTICS The LP2985 was designed to work with ceramic capacitors on the output to take advantage of the benefits they offer: for capacitance values in the 2.2 F to 4.7 F range, ceramics are the least expensive and also have the lowest ESR values (which makes them best for eliminating high-frequency noise). The ESR of a typical 2.2 F ceramic capacitor is in the range of 10 m to 20 m, which easily meets the ESR limits required for stability by the LP2985. One disadvantage of ceramic capacitors is that their capacitance can vary with temperature. Most large value ceramic capacitors ( 2.2 F) are manufactured with the Z5U or Y5V temperature characteristic, which results in the capacitance dropping by more than 50% as the temperature goes from 25C to 85C. This could cause problems if a 2.2 F capacitor were used on the output since it will drop down to approximately 1 F at high ambient temperatures (which could cause the LM2985 to oscillate). If Z5U or Y5V capacitors are used on the output, a minimum capacitance value of 4.7 F must be observed. A better choice for temperature coefficient in ceramic capacitors is X7R, which holds the capacitance within 15%. Unfortunately, the larger values of capacitance are not offered by all manufacturers in the X7R dielectric. Tantalum: Tantalum capacitors are less desirable than ceramics for use as output capacitors because they are more expensive when comparing equivalent capacitance and voltage ratings in the 1 F to 4.7 F range. Another important consideration is that Tantalum capacitors have higher ESR values than equivalent size ceramics. This means that while it may be possible to find a Tantalum capacitor with an ESR value within the stable range, it would have to be larger in capacitance (which means bigger and more costly) than a ceramic capacitor with the same ESR value. It should also be noted that the ESR of a typical Tantalum will increase about 2:1 as the temperature goes from 25C down to -40C, so some guard band must be allowed.
DS100140-7
Important: The output capacitor must maintain its ESR within the stable region over the full operating temperature range of the application to assure stability. The LP2985 requires a minimum of 2.2 F on the output (output capacitor size can be increased without limit). It is important to remember that capacitor tolerance and variation with temperature must be taken into consideration when selecting an output capacitor so that the minimum required amount of output capacitance is provided over the full
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Application Hints
ON/OFF INPUT OPERATION
(Continued)
The LP2985 is shut off by driving the ON/OFF input low, and turned on by pulling it high. If this feature is not to be used, the ON/OFF input should be tied to VIN to keep the regulator output on at all times. To assure proper operation, the signal source used to drive the ON/OFF input must be able to swing above and below the specified turn-on/turn-off voltage thresholds listed in the Electrical Characteristics section under VON/OFF. To prevent mis-operation, the turn-on (and turn-off) voltage signals applied to the ON/OFF input must have a slew rate which is 40 mV/s. Caution: the regulator output voltage can not be guaranteed if a slow-moving AC (or DC) signal is applied that is in the range between the specified turn-on and turn-off voltages listed under the electrical specification VON/OFF (see Electrical Characteristics).
REVERSE INPUT-OUTPUT VOLTAGE The PNP power transistor used as the pass element in the LP2985 has an inherent diode connected between the regulator output and input. During normal operation (where the input voltage is higher than the output) this diode is reverse-biased. However, if the output is pulled above the input, this diode will turn ON and current will flow into the regulator output. In such cases, a parasitic SCR can latch which will allow a high current to flow into VIN (and out the ground pin), which can damage the part. In any application where the output may be pulled above the input, an external Schottky diode must be connected from VIN to VOUT (cathode on VIN, anode on VOUT), to limit the reverse voltage across the LP2985 to 0.3V (see Absolute Maximum Ratings).
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LP2985 Micropower SOT, 150 mA Low-Noise Ultra Low-Dropout Regulator
Physical Dimensions
inches (millimeters) unless otherwise noted
5-Lead Small Outline Package (M5) NS Package Number MA05B
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