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MIC29710/29712
Micrel
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 PNPTM process. The MIC29710/2 is available in two versions: the three pin fixed output MIC29710 and the five pin adjustable output voltage MIC29712. All 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 may be continuously enabled by connecting EN to IN. The MIC29710/2 is available in the standard three and five pin TO-220 package with an operating junction temperature range of 0C to +125C.
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) No minimum load current Fixed voltage and adjustable versions
Applications
* PentiumTM, Pentium PlusTM, and Power PCTM processor supplies * High-efficiency "green" computer systems * High-efficiency linear power supplies * High-efficiency switching supply post regulator * Battery-powered equipment
For applications requiring even lower dropout voltage or input voltage greater than 16V, see the MIC29750/29752.
Ordering Information
Part Number MIC29710-3.3BT MIC29710-5.0BT MIC29712BT
* Junction Temperature
Temp. Range* 0C to +125C 0C to +125C 0C to +125C
Voltage 3.3V 5.0V Adj.
Current 7.5A 7.5A 7.5A
Package TO-220-3 TO-220-3 TO-220-5
Typical Application
MIC29710 VIN IN OUT VOUT
On Off
MIC29712 EN IN GND OUT R1 VIN ADJ R2 VOUT
GND
VOUT = 1.240
R1 1 R2
Fixed Regulator Configuration
Adjustable Regulator Configuration
3-104
1997
MIC29710/29712
Micrel
Pin Configuration
123
12345
MIC29710BT
MIC29712BT
On all devices, the Tab is grounded.
Pin Description
3-Pin TO-220 (MIC29710)
Pin Number 1 2 3 Pin Name IN GND OUT Pin Function Unregulated Input: +16V maximum supply. Ground: Internally connected to tab (ground). Regulated Output
3
5-Pin TO-220 (MIC29712)
Pin Number 1 2 3 4 5 Pin Name EN IN GND OUT ADJ Pin Function 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.
Absolute Maximum Ratings
Input Supply Voltage, Note 1 ...................... -0.7 V to +20V Power Dissipation .................................... Internally Limited Storage Temperature Range ................... -65C to +150C Lead Temperature (Soldering, 5 sec.) ...................... 260C
Operating Ratings
Operating Junction Temperature ................. 0C to +125C JC (TO-220) ............................................................. 2C/W JA (TO-220) ........................................................... 55C/W
1997
3-105
MIC29710/29712
Micrel
Electrical Characteristics
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 2 IO = 10mA, (VOUT + 1V) VIN 8V VIN = VOUT + 1V, 10mA IOUT 7.5A, Notes 2, 6 VO/T, Note 6 VOUT = - 1%, (Note 3) MIC29710/29712 IO = 100mA IO = 750mA IO = 1.5A IO = 3A IO = 5A IO = 7.5A MIC29710/29712 IO = 750mA, VIN = VOUT + 1V IO = 1.5A IO = 3A IO = 5A IO = 7.5A Min -2 0.06 0.2 20 Typ Max 2 0.5 1 100 Units % % % ppm/C
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
375 2 15
IGNDDO Ground Pin Current at Dropout Current Limit en, Output Noise Voltage (10Hz to 100kHz) VOUT = 5.0V Reference (MIC29712 only) 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 4 CL = 47F Io = 100mA
10mA IO 7.5A, VOUT + 1V VIN 8V, Note 2
1.215
1.240 40
1.265 80 120
VMAX nA nA ppm/C nA/C
Note 7
20 0.1
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1997
MIC29710/29712
Parameter 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
General Note: Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Note 8:
Micrel
Conditions Min Typical Max Units
0.8 2.4 15 - 10 20 30 75 2 4
V V A A A A A A
(Note 8)
Devices are ESD sensitive. Handling precautions are recommended.
The maximum continuous supply voltage is 16V. For testing, MIC29712 VOUT is programmed to 5V. 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. For this test, VIN is the larger of 8V or VOUT + 3V. 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. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. VREF VOUT (VIN - 1 V), 2.4V VIN 8V, 10mA < IL 7.5A, TJ TJ MAX. VEN 0.8V and VIN 16V, VOUT = 0.
3
Block Diagram
IN EN On/Off Bias O.V. ILIMIT 28V 16V Reference OUT
Feedback Thermal Shutdown
ADJ
GND
1997
3-107
MIC29710/29712
Micrel
Typical Characteristics
MIC29712 Load Transient Response (See Test Circuit Schematic)
MIC29712 EN VIN = VOUT + 1V IN GND ADJ 49.9k 1% OUT 0.1F 93.1k 1%
OUTPUT VOLTAGE
VOUT 3.525V nominal 6 x 330F AVX TPSE337M006R0100 tantalum
+50mV 3.525V -50mV 1ms/division 8A 6A 4A 2A 200mA 0A
VOUT load (not shown): Intel(R) Power Validator
LOAD CURRENT
MIC29712 Load Transient Response Test Circuit
MIC29712 Line Transient Response with 10mA Load, 10F Output Capacitance
MIC29712 Line Transient Response with 10mA Load, 100F Output Capacitance
INPUT VOLTAGE
6.525V 4.525V 200s/division IOUT = 10mA COUT =10F
INPUT VOLTAGE
6.525V 4.525V 200s/division IOUT = 10mA COUT = 100F
OUTPUT VOLTAGE
OUTPUT VOLTAGE
+20mV 3.525V -20mV
+20mV 3.525V -20mV
MIC29710/2 Dropout Voltage vs. Output Current
0.6
MIC29710/2 Dropout Voltage vs. Temperature
1.0
4
MIC29710-3.3 Dropout Characteristics
DROPOUT VOLTAGE (V)
DROPOUT VOLTAGE (V)
0.5 0.4 0.3 0.2 0.1 0 0 2 4 6 OUTPUT CURRENT (A) 8
0.8 0.6 0.4 0.2 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C) ILOAD = 7.5A
OUTPUT VOLTAGE (V)
3 ILOAD = 10mA 2 ILOAD = 7.5A
1
0
0
4 8 12 INPUT VOLTAGE (V)
16
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1997
MIC29710/29712
Micrel
MIC29710/2 Ground Current vs. Input Voltage
10 350 IOUT = 10mA
MIC29710/2 Ground Current vs. Input Voltage
12
MIC29710/2 Ground Current vs. Temperature
GROUND CURRENT (mA)
10 8 6 4 2 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C) IOUT = 750mA VIN = VOUT + 1
GROUND CURRENT (mA)
GROUND CURRENT (mA)
8 6 4 2 0
300 250 200 150 100 50 0 0
IOUT = 7.5A
0
2 4 6 INPUT VOLTAGE (V)
8
2 4 6 INPUT VOLTAGE (V)
8
MIC29710/2 Ground Current vs. Temperature
50 350
MIC29710/2 Ground Current vs. Temperature
250
MIC29710/2 Ground Current vs. Output Current
GROUND CURRENT (mA)
GROUND CURRENT (mA)
GROUND CURRENT (mA)
40 30 20 10 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C) IOUT = 3.75A VIN = VOUT + 1
300 250 200 150 100 50 0 -100 -50 0 50 100 TEMPERATURE (C) 150 IOUT = 7.5A VIN = VOUT + 1
200 150 100 50 0 VIN = VOUT + 1
3
0
2 4 6 OUTPUT CURRENT (A)
8
MIC29710-3.3 Output Voltage vs. Temperature
3.40 OUTPUT VOLTAGE (V) 3.38 3.36 CURRENT (A) 3.34 3.32 3.30 3.28 3.26 3.24 3 DEVICES 12 10 8 6 4 2
MIC29710/2 Short Circuit Current vs. Temperature
ENABLE CURRENT (A)
40 35 30 25 20 15 10 5
MIC29712 Enable Current vs. Temperaure
VEN = 5V
VOUT = 0V
VEN = 2V
3.22 3.20 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
50 ADJUST PIN CURRENT (nA) 40 30 20 10
MIC29712 Adjust Pin Current vs. Temperature
OUTPUT IMPEDANCE ()
MIC29710/2 Output Impedance vs. Frequency
10
1
0.1
0.01
10x100
100x100
1x103
10x103
100x103
FREQUENCY (Hz)
1997
3-109
1x106
0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
0.001
MIC29710/29712
Micrel
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: TJ MAX - TA SA = ------------ - (JC + CS) PD Where TJ MAX 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. 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.
Applications Information
The MIC29710 and MIC29712 are high performance lowdropout voltage regulators suitable for all moderate to highcurrent voltage regulator applications. Their 700mV of dropout 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 base-emitter 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. The MIC29710/ 712 does not have a minimum load current limitation. A trade-off for the low dropout voltage is a varying base drive requirement. But Micrel's Super eta PNPTM 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 highcurrent Super eta PNPTM regulators have identical pinouts.
VIN
VOUT
Figure 3. The MIC29710 requires only two capacitors for operation. 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
3-110
1997
MIC29710/29712
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: VOUT R1 = R2 x ( ------ - 1) 1.240 Where VO is the desired output voltage. Figure 4 shows component definition.
Micrel
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 microamperes 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.
Voltage
MIC29712BT
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
VIN 4.75 to 5.25 10F
VOUT R1 100k 33F R2 56.2k 3.45V
2.85 2.9 3.0 3.1 3.15 3.3 3.45 3.525 3.6 3.8 4.0 4.1
3
Figure 5. MIC29712 Resistor Table
VOUT = 1.240V x [1 + (R1 / R2)]
Figure 4. Adjustable Regulator with Resistors
1997
3-111

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