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MIC5238
Ultra-Low Quiescent Current, 150mA Cap LDO Regulator
General Description
The MIC5238 is an ultra-low voltage output, 150mA LDO regulator. Designed to operate in a single supply or dual supply mode, the MIC5238 consumes only 23A of bias current, improving efficiency. When operating in the dual supply mode, the efficiency greatly improves as the higher voltage supply is only required to supply the 23A bias current while the output and base drive comes off of the much lower input supply voltage. As a Cap regulator, the MIC5238 operates with a 2.2F ceramic capacitor on the output, offering a smaller overall solution. It also incorporates a logic-level enable pin that allows the MIC5238 to be put into a zero off-current mode when disabled. The MIC5238 is fully protected with current limit and (R) thermal shutdown. It is offered in the IttyBitty SOT-23-5 package with an operating junction temperature range of -40C to +125C. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* * * * * * * * * * Ultra-low input voltage range:1.5V to 6V Ultra-low output voltage:1.0V minimum output voltage Low dropout voltage: 310mV at 150mA High output accuracy: 2.0% over temperature Cap: stable with ceramic or tantalum capacitors Excellent line and load regulation specifications Zero shutdown current Reverse leakage protection Thermal shutdown and current limit protection IttyBitty(R) SOT-23-5 package
Applications
* * * * PDAs and pocket PCs Cellular phones Battery powered systems Low power microprocessor power supplies
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Typical Application
Ultra-Low Voltage Application
IttyBitty is a registered trademark of Micrel, Inc. Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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Ordering Information
Part Number Standard MIC5238-1.0BM5 MIC5238-1.1BM5 MIC5238-1.3BM5 MIC5238-1.0BD5 MIC5238-1.1BD5 MIC5238-1.3BD5
Notes: * Under bar symbol ( _ ) may not be to scale. ** Other voltage options available. Contact Micrel Marketing for details.
Voltage** Marking Code* L410 L411 L413 N410 N411 N413 1.0V 1.1V 1.3V 1.0V 1.1V 1.3V
Marking Code L410 L411 L413 N410 N411 N413
Pb-Free MIC5238-1.0YM5 MIC5238-1.1YM5 MIC5238-1.3YM5 MIC5238-1.0YD5 MIC5238-1.1YD5 MIC5238-1.3YD5
Junction Temp. Range -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C
Package SOT-23-5 SOT-23-5 SOT-23-5 TSOT-23-5 TSOT-23-5 TSOT-23-5
Pin Configuration
5-Pin SOT-23 (M5)
5-Pin Thin SOT-23 (D5)
Pin Description
Pin Number 1 2 3 4 5 Pin Name IN GND EN BIAS OUT Pin Function Supply Input Ground Enable (Input): Logic Low = shutdown; Logic High = enable. Don not leave open. Bias Supply Input Regulator Output
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Absolute Maximum Ratings(1)
Input Supply Voltage (VIN)................................. -0.3V to 7V BIAS Supply Voltage (VBIAS).............................. -0.3V to 7V Enable Supply Voltage (VEN)............................. -0.3V to 7V Power Dissipation (PD). .............................Internally Limited Junction Temperature (TJ) ........................-40C to +125C Storage Temperature (TS).........................-65C to +150C ESD Rating(3) ......................................................1.5A HBM
Operating Ratings(2)
Supply Voltage (VIN)............................................ 1.5V to 6V BIAS Supply Voltage (VBIAS)................................ 2.3V to 6V Enable Supply Voltage (VEN).................................. 0V to 6V Junction Temperature (TJ) ........................ -40C to +125C Package Thermal Resistance SOT-23-5 (JA) .................................................235C/W
Electrical Characteristics(4)
TA = 25C with VIN = VOUT + 1V; VBIAS = 3.3V; IOUT = 100A; VEN = 2V, bold values indicate -40C < TJ < +125C, unless specified.
Parameter Output Voltage Accuracy Line Regulation Input Line Regulation Load Regulation Dropout Voltage Condition Variation from nominal VOUT VBIAS = 2.3V to 6V, Note 5 VIN = (VOUT 1V) to 6V Load = 100A to 150mA IOUT = 100A IOUT = 50mA IOUT = 100mA IOUT = 150mA BIAS Current, Note 6 Input Current, Pin 1 IOUT = 100A IOUT = 100A IOUT = 50mA, Note 7 IOUT = 100mA IOUT = 150mA Ground Current in Shutdown Short Circuit Current Reverse Leakage VEN 0.2V, VIN = 6V, VBIAS = 6V VEN = 0V, VIN = 6V, VBIAS = 6V VOUT = 0V VIN = 0V, VEN = 0V, VOUT = nom VOUT Min -1.5 -2 0.25 0.04 0.7 50 230 270 310 23 7 0.35 1 2 1.5 0.5 350 5 500 2.5 5 20 450 500 300 400 Typ Max +1.5 +2 0.5 4 1 Units % % % % % mV mV mV mV mV mV A A mA mA mA A A mA A
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Electrical Characteristics(4) cont.
TA = 25C with VIN = VOUT + 1V; VBIAS = 3.3V; IOUT = 100A; VEN = 2V, bold values indicate -40C < TJ < +125C, unless specified.
Parameter Enable Input Input Low Voltage Input High Voltage Enable Input Current
Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. 4. Specification for packaged product only. 5. Line regulation measures a change in output voltage due to a change in the bias voltage. 6. Current measured from bias input to ground. 7. Current differential between output current and main input current at rated load current.
Condition Regulator OFF Regulator ON VEN = 0.2V, Regulator OFF VEN = 0.2V, Regulator ON
Min
Typ
Max 0.2
Units V V A A
2.0 -1.0 0.01 0.1 1.0 1.0
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Typical Characteristics
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Typical Characteristics cont.
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Functional Characteristics
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Functional Diagram
Block Diagram - Fixed Output Voltage
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MIC5238 TJ(MAX) is the maximum junction temperature of the die, 125C, and TA is the ambient operating temperature. JA is layout dependent; Table 1 shows the junction-to-ambient thermal resistance for the MIC5238.
Package SOT-23-5 JA Recommended Minimum Footprint 235C/W
Application Information
Enable/Shutdown The MIC5238 comes with an active-high enable pin that allows the regulator to be disabled. Forcing the enable pin low disables the regulator and sends it into a "zero" offmode-current state. In this state, current consumed by the regulator goes nearly to zero. Forcing the enable pin high enables the output voltage. Input Bias Capacitor The input capacitor must be rated to sustain voltages that may be used on the input. An input capacitor may be required when the device is not near the source power supply or when supplied by a battery. Small, surface mount, ceramic capacitors can be used for bypassing. Larger values may be required if the source supply has high ripple. Output Capacitor The MIC5238 requires an output capacitor for stability. The design requires 2.2F or greater on the output to maintain stability. The design is optimized for use with low-ESR ceramic chip capacitors. High ESR capacitors may cause high frequency oscillation. The maximum recommended ESR is 3. The output capacitor can be increased without limit. Larger valued capacitors help to improve transient response. X7R/X5R dielectric-type ceramic capacitors are recommended because of their temperature performance. X7Rtype capacitors change capacitance by 15% over their operating temperature range and are the most stable type of ceramic capacitors. Z5U and Y5V dielectric capacitors change value by as much as 50% and 60% respectively over their operating temperature ranges. To use a ceramic chip capacitor with Y5V dielectric, the value must be much higher than a X7R ceramic capacitor to ensure the same minimum capacitance over the equivalent operating temperature range. No-Load Stability The MIC5238 will remain stable and in regulation with no load unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. Thermal Considerations The MIC5238 is designed to provide 150mA of continuous current in a very small package. Maximum power dissipation can be calculated based on the output current and the voltage drop across the part. To determine the maximum power dissipation of the package, use the junction-to-ambient thermal resistance of the device and the following basic equation:
PD(MAX) = TJ(max) - TA
Table 1. SOT-23-5 Thermal Resistance
The actual power dissipation of the regulator circuit can be determined using the equation: PD = (VIN - VOUT) IOUT + VINIGND Substituting PD(MAX) for PD and solving for the operating conditions that are critical to the application will give the maximum operating conditions for the regulator circuit. For example, when operating the MIC5238-1.0BM5 at 50C with a minimum footprint layout, the maximum input voltage for a set output current can be determined as follows.
PD(MAX) = 125C - 50C 235C/W
JA
PD(MAX) = 319mW The junction-to-ambient (JA) thermal resistance for the minimum footprint is 235C/W, from Table 1. It is important that the maximum power dissipation not be exceeded to ensure proper operation. With very high input-to-output voltage differentials, the output current is limited by the total power dissipation. Total power dissipation is calculated using the following equation: PD = (VIN - VOUT) IOUT + VIN x IGND + VBIAS x IBIAS Since the bias supply draws only 18A, that contribution can be ignored for this calculation. If we know the maximum load current, we can solve for the maximum input voltage using the maximum power dissipation calculated for a 50C ambient, 319mV. PD(MAX) = (VIN - VOUT) IOUT + VIN x IGND 319mW = (VIN - 1V) 150mA + VIN x 2.8mA Ground pin current is estimated using the typical characteristics of the device. 469mW = VIN (152.8mA) VIN = 3.07V For higher current outputs only a lower input voltage will work for higher ambient temperatures. Assuming a lower output current of 20mA, the maximum input voltage can be recalculated: 319mW = (VIN - 1V) 20mA + VIN x 0.2mA 339mW = VIN x 20.2mA VIN = 16.8V Maximum input voltage for a 20mA load current at 50C ambient temperature is 16.8V. Since the device has a 6V rating, it will operate over the whole input range. 9
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Micrel, Inc. Dual Supply Mode Efficiency By utilizing a bias supply the conversion efficiency can be greatly enhanced. This can be realized as the higher bias supply will only consume a few A's while the input supply will require a few mA's. This equates to higher efficiency saving valuable power in the system. As an example, consider an output voltage of 1V with an input supply of 2.5V at a load current of 150mA. The input ground current under these conditions is 2mA, while the bias current is only 20A. If we calculate the conversion efficiency using the single supply approach, it is as follows: Input power = VIN x output current + VIN x (VBIAS ground current + VIN ground current) Input power = 2.5V x 150mA + 2.5 x (0.0002+0.002) = 380.5mW Output power = 1V x 0.15 = 150mW Efficiency = 150/380.5 x 100 = 39.4%
MIC5238 Now, using a lower input supply of 1.5V, and powering the bias voltage only from the 2.5V input, the efficiency is as follows: Input power = VIN x output current + VIN x VIN ground current + VBIAS x VBIAS ground current Input power = 1.5 x 150mA + 1.5 x 0.002 + 2.5 x 0.0002 = 225mW Output power = 1V x 150mA = 150mW Efficiency = 150/225 x 100 = 66.6 % Therefore, by using the dual supply MIC5238 LDO the efficiency is nearly doubled over the single supply version. This is a valuable asset in portable power management applications equating to longer battery life and less heat being generated in the application. This in turn will allow a smaller footprint design and an extended operating life.
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Package Information
5-Pin SOT-23 (M5)
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Package Information cont.
5-Pin Thin SOT-23 (D5)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2003 Micrel, Incorporated.
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