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| 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 SOT-223 FEATURES *Fixed and adjustable output voltages to 1.24V *410mV typical dropout at 1A Ideal for 3.0V to 2.5V conversion Ideal for 2.5V to 1.8V or 1.5V conversion *1A minimum guaranteed output current *1% initial accuracy LM39100-X.X Fixed *Low ground current *Current limiting and thermal shutdown SOP-8 *Reversed-battery protection *Reversed-leakage protection *Fast transient response *Low-profile SOT-223 package APPLICATIONS *LDO linear regulator for PC add-in cards *PowerPCTM power supplies *High-efficiency linear power supplies *SMPS post regulator *Multimedia and PC processor supplies *Battery chargers *Low-voltage microcontrollers and digital logic PIN DESCRIPTION CMOS-compatible control input. Enable (Input) IN OUT FLG ADJ GND Logic high = enable, logic Logic low or open = shutdown Supply (Input) Regulator Output Flag (Output): Open-collector error flag output. Adjustment Input: Feedback input. Connect to resitive voltage-divider network Connect to resitive voltage-divider network Ground ORDERING INFORMATION Device LM39100- X.X LM39101-X.X LM39102-Adj Marking LM39100-X.X LM39101-X.X LM39102-Adj Package SOT-223 SOP-8 SOP-8 DESCRIPTION * X.X = Fixed Vout = 1.5V, 1.8V, 2.5V, 3.3V, 5.0V The LM39100, LM39101, and LM39102 are 1A low-dropout linear voltage regulators that provide lowvoltage,high-current output from an extremely small package. The LM39100/1/2 offers extremely low dropout (typically 410mVat 1A) and low ground current (typically 12mA at 1A). The LM39100 is a fixed output regulator offered in theSOT-223 package. The LM39101 and LM39102 are fixedand adjustable regulators, respectively, in a thermally en-hanced power 8-lead SOP (small outline package). The LM39100/1/2 is ideal for PC add-in cards that need toconvert from standard 5V to 3.3V, 3.3V to 2.5V or 2.5V to1.8V. A guaranteed maximum dropout voltage of 630mV overall operating conditions allows the LM39100/1/2 to provide2.5V from a supply as low as 3.13V and 1.8V from a supplyas low as 2.43V. The LM39100/1/2 is fully protected with over current limiting,thermal shutdown, and reversed-battery protection. Fixed voltages of 5.0V, 3.3V, 2.5V,1.8V and 1.5V are available on LM39100/1 with adjustable output voltages to 1.24V on LM39102. HTC 1 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 Typical Application Circuit Absolute Maximum Ratings (Note 1) Supply Voltage (VIN) Enable Voltage (VEN) Storage Temperature (TS) Lead Temperature (soldering, 5 sec) ESD, Note 3 Operating Ratings (Note 2) Supply Voltage (VIN) Enable Voltage (VEN) Maximum Power Dissipation (PD(max)) Junction Temperature (TJ) Package Thermal Resistance SOT-223 (JC) SOP-8 (JC) +2.25V to +16V +16V Note 4 -20V to +20V +20V -65C to +150C 260C -40C to +125C 15C/W 20C/W HTC 2 1A Low-Voltage Low-Dropout Regulator Block Diagram LM39100/39101/39102 LM39100 Fixed (1.5V,1.8V,2.5V,3.3V,5.0V) LM39100 Fixed with Flag and Enable LM39102 Adjustable HTC 3 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 HTC 4 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 TYPICAL PERFORMANCE CHARACTERISTICS HTC 5 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 HTC 6 1A Low-Voltage Low-Dropout Regulator APPLICATION INFORMATION LM39100/39101/39102 The LM39100/1/2 is a high-performance low-dropout voltage regulator suitable for moderate to high-current voltage regulator applications. Its 630mV dropout voltage at full loadand over temperature makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. Unlike older NPN-pass transistor de-signs, where the minimum dropout voltage is limited by thebase-to-emitter voltage drop and collector-to-emitter satura-tion voltage, dropout performance of the PNP output of these devices is limited only by the low VCE saturation voltage.A trade-off for the low dropout voltage is a varying base drive requirement. The LM39100/1/2 regulator is fully protected from damage due to fault conditions. Linear current limiting is provided.Output current during overload conditions is constant. Thermal shutdown disables the device when the die temperature exceeds the maximum safe operating temperature. Tran-sient protection allows device (and load) survival even when the input voltage spikes above and below nominal. The output structure of these regulators allows voltages in excess of the desired output voltage to be applied without reverse current flow. Output Capacitor The LM39100/1/2 requires an output capacitor to maintain stability and improve transient response. Proper capacitor selection is important to ensure proper operation. The LM39100/1/2 output capacitor selection is dependent upon the ESR (equivalent series resistance) of the output capacitor to maintain stability. When the output capacitor is 10F orgreater, the output capacitor should have an ESR less than 2. This will improve transient response as well as promote stability. Ultra-low-ESR capacitors (<100m), such as ce-ramic chip capacitors, may promote instability. These very low ESR levels may cause an oscillation and/or underdamped transient response. A low-ESR solid tantalum capacitor works extremely well and provides good transient response and stability over temperature. Aluminum electrolytics can also be used, as long as the ESR of the capacitor is <2.The value of the output capacitor can be increased without limit. Higher capacitance values help to improve transient response and ripple rejection and reduce output noise. Input Capacitor An input capacitor of 1F or greater is recommended whenthe device is more than 4 inches away from the bulk ac supply capacitance or when the supply is a battery. Small, surfacemount, ceramic chip capacitors can be used for bypassing. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further improving the integrity of the output voltage. Error Flag The LM39101 features an error flag (FLG), which monitors the output voltage and signals an error condition when this voltage drops 5% below its expected value. The error flag isan open-collector output that pulls low under fault conditions and may sink up to 10mA. Low output voltage signifies anumber of possible problems, including an overcurrent fault(the device is in current limit) or low input voltage. The flag output is inoperative during overtemperature conditions. Apull-up resistor from FLG to either VIN or VOUT is required for proper operation. For information regarding the minimum and maximum values of pull-up resistance, refer to the graph in the typical characteristics section of the data sheet. Enable Input The LM39101 and LM39102 versions feature an active-high enable input (EN) that allows on-off control of the regulator. Current drain reduces to "zero" when the device is shutdown, with only micro amperes of leakage current. The EN input has TTL/CMOS compatible thresholds for simple logic interfacing. EN may be directly tied to VIN and pulled upto the maximum supply voltage Transient Response and 3.3V to 2.5V or 2.5V to 1.8V Conversion The LM39100/1/2 has excellent transient response to varia-tions in input voltage and load current. The device has been designed to respond quickly to load current variations and input voltage variations. Large output capacitors are not required to obtain this performance. A standard 10F output capacitor, preferably tantalum, is all that is required. Larger values help to improve performance even further. By virtue of its low-dropout voltage, this device does not saturate into dropout as readily as similar NPN-based designs. When converting from 3.3V to 2.5V or 2.5V to 1.8V, the NPN based regulators are already operating in dropout, withtypical dropout requirements of 1.2V or greater. To convertdown to 2.5V or 1.8V without operating in dropout, NPN-based regulators require an input voltage of 3.7V at the veryleast. The LM39100 regulator will provide excellent perfor-mance with an input as low as 3.0V or 2.5V respectively. This gives the PNP based regulators a distinct advantage overolder, NPN based linear regulators. HTC 7 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 Minimum Load Current The LM39100/1/2 regulator is specified between finite loads.If the output current is too small, leakage currents dominate and the output voltage rises. A 10mA minimum load current is necessary for proper regulation. Adjustable Regulator Design The LM39102 allows programming the output voltage any-where between 1.24V and the 16V maximum operating rating of the family. Two resistors are used. Resistors can be quite large, up to 1M, because of the very high input impedance and low bias current of the sense comparator: The resistor values are calculated by : R1=R2(Vout/1.240- 1) Where VO is the desired output voltage. Figure 1 shows component definition. Applications with widely varying load currents may scale the resistors to draw the minimum load current required for proper operation (see below). Power SOP-8 Thermal Characteristics One of the secrets of the LM39101/2's performance is its power SO-8 package featuring half the thermal resistance of a standard SO-8 package. Lower thermal resistance means more output current or higher input voltage for a given package size.Lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to create a single-piece electrical and thermal conductor. This concept hasbeen used by MOSFET manufacturers for years, proving very reliable and cost effective for the user.Thermal resistance consists of two main elements, JC(junction-to-case thermal resistance) and CA (case-to-ambient thermal resistance). See Figure2. JC is the resistance from the die to the leads of the package. CA is the resistance from the leads to the ambient air and it includes CS (case-to-sink thermal resistance) and SA (sink-to-ambient thermal resistance).Using the power SOP8 reduces the JC dramatically and allows the user to reduce CA. The total thermal resistance,JA (junction-toambient thermal resistance) is the limiting factor in calculating the maximum power dissipation capabil-ity of the device. Typically, the power SOP-8 has a JC of20C/W, this is significantly lower than the standard SOP-8 which is typically 75C/W. CA is reduced because pins 5 through 8 can now be soldered directly to a ground plane which significantly reduces the case-to-sink thermal resis-tance and sink to ambient thermal resistance.Low-dropout linear regulators from HTC are rated to amaximum junction temperature of 125C. It is important not to exceed this maximum junction temperature during operation of the device. To prevent this maximum junction temperature from being exceeded, the appropriate ground plane heatsink must be used. Figure3 shows copper area versus power dissipation with each trace corresponding to a different temperature rise above ambient.From these curves, the minimum area of copper necessary for the part to operate safely can be determined. The maxi-mum allow able temperature rise must be calculated to deter-mine operation along which curve. T = TJ(max) - TA(max) TJ(max) = 125C TA(max) = maximum ambient operating temperature For example, the maximum ambient temperature is 50C, theT is determined as follows: T = 125C - 50C T = 75C HTC 8 1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102 Using Figure3, the minimum amount of required copper can be determined based on the required power dissipation.Power dissipation in a linear regulator is calculated as fol-lows: PD = (VIN - VOUT) IOUT + VIN*IGND If we use a 2.5V output device and a 3.3V input at an output current of 1A, then our power dissipation is as follows: PD = (3.3V - 2.5V) x 1A + 3.3V x 11mA PD = 800mW + 36mW PD = 836mW From Figure3, the minimum amount of copper required too perate this application at a T of 75C is 160mm2. Quick Method Determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. Refer to Figure4, which shows safe operating curves for three different ambient temperatures:25C, 50C and 85C. From these curves, the minimum amount of copper can be determined by knowing the maxi-mum power dissipation required. If the maximum ambient temperature is 50C and the power dissipation is as above,836mW, the curve in Figure5 shows that the required area of copper is 160.The JA of this package is ideally 63C/W, but it will vary depending upon the availability of copper ground plane to which it is attached. HTC 9 |
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