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MIC29710/29712
7.5A Fast-Response LDO Regulator
General Description
The MIC29710 and MIC29712 are high-current, high-accuracy, low-dropout voltage regulators featuring fast transient recovery from input voltage surges and output load current changes. These regulators use a PNP pass element that features Micrel's proprietary Super eta PNP(R) process. The MIC29710 is available in the 3-pin fixed output and the MIC29712 is available in the 5-pin adjustable output voltage. Both versions are fully protected against overcurrent faults, reversed lead insertion, overtemperature operation, and positive and negative transient voltage spikes. A TTL compatible enable (EN) control pin supports external on/off control. If on/off control is not required, the device maybe continuously enabled by connecting EN to IN. The MIC29710 is available in the standard 3-pin TO-220 package the MIC29712 is available in the 5-pin TO-220 package with an operating junction temperature range of 0C to +125C. For applications requiring even lower dropout voltage or input voltage greater than 16V, see the MIC29750/29752. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
Features
* * * * * * * Fast transient response 7.5A current capability 700mV dropout voltage at full load Low ground current Accurate 2% guaranteed tolerance "Zero" current shutdown mode (MIC29712) Fixed voltage and adjustable versions
Applications
* Pentium(R), Pentium(R) Plus, and Power PC(R) processor supplies * High-efficiency "green" computer systems * High-efficiency linear power supplies * High-efficiency switching supply post regulator * Battery-powered equipment
Typical Application
R1 VOUT = 1.240 + 1 R2
Fixed Regulator Configuration Adjustable Regulator Configuration
Super eta PNP is a registered trademark of Micrel, Inc. Pentium is a registered trademark of Intel Corporation. PowerPC is a registered trademark of IBM Corporation. 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(1)
Part Number Standard MIC29710-3.3BT MIC29710-5.0BT MIC29712BT
Note: * RoHS Compliant with `high-melting solder' exemption.
RoHS Compliant* MIC29710-3.3WT MIC29710-5.0WT MIC29712WT
Voltage 3.3V 5.0V Adj
Junction Temp. Range 0C to +125C 0C to +125C 0C to +125C
Package 3-Pin TO-220 3-Pin TO-220 5-Pin TO-220
Pin Configuration
123
MIC29710BT/WT On both devices, the Tab is grounded
12345
MIC29712BT/WT
Pin Description
Pin Number 3-Pin TO-220 - 1 2 3 - Pin Number 5-Pin TO-220 1 2 3 4 5 Pin Name EN IN GND OUT ADJ Pin Name Enable (Input): Logic-level ON/OFF control. Unregulated Input: +16V maximum supply. Ground: Internally connected to tab (ground). Regulated Output Output Voltage Adjust: 1.240V feedback from external resistive divider.
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Absolute Maximum Ratings
Input Supply Voltage (VIN) ......................... -0.7V to +20V Power Dissipation. ....................................Internally Limited Lead Temperature (soldering, 5 sec.)........................ 260C Storage Temperature (Ts) ........................... -65C to 150C EDS Rating(2)
(1)
Operating Ratings
Junction Temperature (TJ) ............................ 0C to +125C Thermal Resistance TO-220 (JC) ........................................................2C/W TO-220 (JA) ......................................................55C/W
Electrical Characteristics(3)
All measurements at TJ = 25C unless otherwise noted. Bold values are guaranteed across the operating temperature range.
Parameter Output Voltage Line Regulation Load Regulation Output Voltage Temperature Coefficient Dropout Voltage Condition 10mA IO 7.5A, (VOUT + 1V) VIN 8V, Note 4 IO = 10mA, (VOUT + 1V) VIN 8V VIN = VOUT + 1V, 10mA IOUT 7.5A, Notes 4, 8 VO/T, Note 8 VOUT = - 1%, Note 5 MIC29710/29712 Min -2 0.06 0.2 20 Typ Max +2 0.5 1 100 Units % % % ppm/C
IO = 100mA IO = 750mA IO = 1.5A IO = 3A IO = 5A IO = 7.5A IO = 750mA, VIN = VOUT + 1V IO = 1.5A IO = 3A IO = 5A IO = 7.5A
80 180 220 300 450 700 6 20 36 100 250 1 11 260
200
1000 20
mV mV mV mV mV mV mA mA mA mA mA mA A VRMS
Ground Current
MIC29710/29712
375 2 15
IGNDDO Ground Pin Current at Dropout Current Limit en, Output Noise Voltage (10Hz to 10kHz) VOUT = 5.0V Reference Voltage Adjust Pin Bias Current Reference Voltage Temperature Coefficient Adjust Pin Bias Current Temperature Coefficient
VIN = 0.5V less than specified VOUT. IOUT = 10mA MIC29710/29712 VOUT = 0V, Note 6 CL = 47F IO = 100mA
Reference (MIC29712 only) 10mA IO 7.5A, VOUT + 1V VIN 8V, Note 4 1.215 1.240 40 Note 9 20 0.1 1.265 80 120 VMAX nA nA ppm/C nA/C
Enable Input (MIC29712 only) Input Logic Voltage Enable (EN) Pin Input Current Low (Off) High (On) VEN = VIN VEN = 0.8V Regulator Output Current in Shutdown Note 10 0.8 2.4 15 - 10 20 30 75 2 4 V V A A A A A A
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Notes: 1. The maximum continuous supply voltage is 16V. 2. Devices are ESD sensitive. Handling precautions are recommended. 3. Specification for packaged product only. 4. For testing, MIC29712 VOUT is programmed to 5V.
MIC29710/29712
5. Dropout voltage is defined as the input-to-output differential when the output voltage drops to 99% of its nominal value with VOUT + 1V applied to VIN. 6. For this test, VIN is the larger of 8V or VOUT + 3V. 7. Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground pin current. 8. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. 9. VREF VOUT (VIN - 1 V), 2.4V VIN 8V, 10mA < IL 7.5A, TJ TJ MAX. 10. VEN 0.8V and VIN 16V, VOUT = 0.
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Typical Characteristics
MIC29710 Load Transient Response Test Circuit
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Functional Diagram
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MIC29710/29712 First, we calculate the power dissipation of the regulator from these numbers and the device parameters from this datasheet. PD = IOUT x (1.03VIN - VOUT) Where the ground current is approximated by 3% of IOUT. Then the heat sink thermal resistance is determined with this formula:
SA = TJMAX - TA - ( JC + CS ) PD
Application Information
The MIC29710 and MIC29712 are high performance low-dropout voltage regulators suitable for all moderate to high-current voltage regulator applications. Their 700mV of drop-out voltage at full load make them especially valuable in battery powered systems and as high efficiency noise filters in "post-regulator" applications. Unlike older NPN-pass transistor designs, where the minimum dropout voltage is limited by the baseemitter voltage drop and collector-emitter saturation voltage, dropout performance of the PNP output of these devices is limited merely by the low VCE saturation voltage. Output regulation is excellent across the input voltage, output current, and temperature ranges. A trade-off for the low dropout voltage is a varying base drive requirement. But Micrel's Super eta PNP(R) process reduces this drive requirement to merely 2 to 5% of the load current. MIC29710/712 regulators are fully protected from damage due to fault conditions. Current limiting is provided. The output current under overload conditions is limited to a constant value. Thermal shutdown disables the device when the die temperature exceeds the maximum safe operating temperature. Transient protection allows device (and load) survival even when the input voltage spike above and below nominal. The MIC29712 version offers a logic level ON/OFF control: when disabled, the devices draw nearly zero current. An additional feature of this regulator family is a common pinout: a design's current requirement may change up or down yet use the same board layout, as all of Micrel's high-current Super eta PNP(R) regulators have identical pinouts.
Where TJMAX 125C and CS is between 0 and 2C/W. The heat sink may be significantly reduced in applications where the minimum input voltage is known and is large compared with the dropout voltage. Use a series input resistor to drop excessive voltage and distribute the heat between this resistor and the regulator. The low dropout properties of Micrel Super eta PNP regulators allow very significant reductions in regulator power dissipation and the associated heat sink without compromising performance. When this technique is employed, a capacitor of at least 0.1F is needed directly between the input and regulator ground. Please refer to Application Note 9 for further details and examples on thermal design and heat sink specification.
Figure 3. The MIC29710 requires only two capacitors for operation
Capacitor Requirements For stability and minimum output noise, a capacitor on the regulator output is necessary. The value of this capacitor is dependent upon the output current; lower currents allow smaller capacitors. MIC29710/2 regulators are stable with a minimum capacitor value of 47F at full load. This capacitor need not be an expensive low ESR type: aluminum electrolytics are adequate. In fact, extremely low ESR capacitors may contribute to instability. Tantalum capacitors are recommended for systems where fast load transient response is important. Where the regulator is powered from a source with a high AC impedance, a 0.1F capacitor connected between Input and GND is recommended. This capacitor should have good characteristics to above 250kHz. Transient Response and 5V to 3.3V Conversion The MIC29710/2 have excellent response to variations in input voltage and load current. By virtue of their low dropout voltage, these devices do not saturate into dropout as readily as similar NPN-based designs. A 3.3V output Micrel LDO will maintain full speed and performance with an input supply as low as 4.2V, and will still provide some regulation with supplies down to 3.8V, unlike NPN devices that require 5.1V or more for good performance and become nothing more than a resistor under 4.6V of input. Micrel's PNP regulators provide superior performance in "5V to 3.3V" conversion applications, especially when all tolerances are considered.
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Thermal Design Linear regulators are simple to use. The most complicated design parameters to consider are thermal characteristics. Thermal design requires the following application-specific parameters:
* * * * Maximum ambient temperature, TA Output Current, IOUT Output Voltage, VOUT Input Voltage, VIN.
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Adjustable Regulator Design The adjustable regulator version, MIC29712, allows programming the output voltage anywhere between 1.25V and the 16V maximum operating rating of the family. Two resistors are used. Resistors can be quite large, up to 100k, because of the very high input impedance and low bias current of the sense comparator. The resistor values are calculated by:
V R1 = R2 x OUT - 1 1.240 Where VO is the desired output voltage. Figure 4 shows component definition.
Enable Input The MIC29712 versions features an enable (EN) input that allows ON/OFF control of the device. Special design allows "zero" current drain when the device is disabled-- only micro-amperes of leakage current flows. The EN input has TTL/CMOS compatible thresholds for simple interfacing with logic, or may be directly tied to VIN. Enabling the regulator requires approximately 20A of current into the EN pin. Minimum Load Current The MIC29710/12 regulators are specified between finite loads. If the output current is to small, leakage currents dominate and the output voltage rises. A 10mA minimum load current is necessary for proper regulation.
Voltage Standard () R1 100k 100k 100k 100k 100k 100k 100k 93.1k 100k 100k 100k 100k R2 76.8k 75.0k 69.8k 66.5k 64.9k 60.4k 56.2k 51.1k 52.3k 48.7k 45.3k 43.2k
MIC29712BT
2.85 2.9 3.0 3.1 3.15 3.3
VIN 4.75 to 5.25 10F
R1 100k 33F R2 56.2k
VOUT 3.45V
3.45 3.525 3.6 3.8 4.0 4.1
VOUT = 1.240Vx [1 + (R1 / R2)]
Figure 4. Adjustable Regulator with Resistors
Figure 5. MIC29712 Resistor Table
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Package Information
3-Pin TO-220 (T)
5-Pin TO-220 (T)
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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) 2004 Micrel, Incorporated.
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