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FEATURES
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LT3012 250mA, 4V to 80V Low Dropout Micropower Linear Regulator DESCRIPTION
The LT(R)3012 is a high voltage, micropower low dropout linear regulator. The device is capable of supplying 250mA of output current with a dropout voltage of 400mV. Designed for use in battery-powered or high voltage systems, the low quiescent current (40A operating and 1A in shutdown) makes the LT3012 an ideal choice. Quiescent current is also well controlled in dropout. Other features of the LT3012 include the ability to operate with very small output capacitors. The regulator is stable with only 3.3F on the output while most older devices require between 10F and 100F for stability. Small ceramic capacitors can be used without any need for series resistance (ESR) as is common with other regulators. Internal protection circuitry includes reverse-battery protection, current limiting, thermal limiting and reverse current protection. The device is available with an adjustable output with a 1.24V reference voltage. The LT3012 regulator is available in the 16-lead TSSOP and 12 pin low profile (0.75mm) (4mm x 3mm) DFN packages with an exposed pad for enhanced thermal handling capability.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Wide Input Voltage Range: 4V to 80V Low Quiescent Current: 40A Low Dropout Voltage: 400mV Output Current: 250mA No Protection Diodes Needed Adjustable Output from 1.24V to 60V 1A Quiescent Current in Shutdown Stable with 3.3F Output Capacitor Stable with Aluminum, Tantalum or Ceramic Capacitors Reverse-Battery Protection No Reverse Current Flow from Output to Input Thermal Limiting Thermally Enhanced 16-Lead TSSOP and 12-Pin (4mm x 3mm) DFN Packages
APPLICATIONS
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Low Current High Voltage Regulators Regulator for Battery-Powered Systems Telecom Applications Automotive Applications
TYPICAL APPLICATION
5V Supply with Shutdown
400 IN VIN 5.4V TO 80V 1F OUT LT3012 SHDN GND ADJ 249k
3012 TA01
Dropout Voltage
VOUT 5V 250mA 3.3F 350 DROPOUT VOLTAGE (mV) 300 250 200 150 100 50 0 0 50 100 150 200 OUTPUT CURRENT (mA) 250
3012 TA02
750k
VSHDN <0.3V >2.0V
OUTPUT OFF ON
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LT3012 ABSOLUTE MAXIMUM RATINGS
(Note 1)
IN Pin Voltage .........................................................80V OUT Pin Voltage ......................................................60V IN to OUT Differential Voltage .................................80V ADJ Pin Voltage ........................................................7V SHDN Pin Input Voltage ..........................................80V Output Short-Circuit Duration .......................... Indefinite
Storage Temperature Range TSSOP Package ................................. -65C to 150C DFN Package...................................... -65C to 125C Operating Junction Temperature Range (Notes 3, 10, 11) LT3012E ............................................. -40C to 125C LT3012HFE......................................... -40C to 140C Lead Temperature (FE16 Soldering, 10 sec) ......... 300C
PIN CONFIGURATION
TOP VIEW TOP VIEW GND NC OUT OUT ADJ GND NC 1 2 3 4 5 6 13 12 NC 11 IN 10 IN 9 8 7 NC SHDN NC NC OUT OUT ADJ GND NC GND DE PACKAGE 12-LEAD (4mm x 3mm) PLASTIC DFN TJMAX = 125C, JA = 40C/W, JC = 16C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB 1 2 3 4 5 6 7 8 17 16 GND 15 NC 14 IN 13 IN 12 NC 11 SHDN 10 NC 9 GND
FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 140C, JA = 40C/W, JC = 16C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH LT3012EDE#PBF LT3012EFE#PBF LT3012HFE#PBF LEAD BASED FINISH LT3012EDE LT3012EFE LT3012HFE TAPE AND REEL LT3012EDE#TRPBF LT3012EFE#TRPBF LT3012HFE#TRPBF TAPE AND REEL LT3012EDE#TR LT3012EFE#TR LT3012HFE#TR PART MARKING 3012 3012EFE 3012HFE PART MARKING 3012 3012EFE 3012HFE PACKAGE DESCRIPTION 12-Lead (4mm x 3mm) Plastic DFN 16-Lead Plastic TSSOP 16-Lead Plastic TSSOP PACKAGE DESCRIPTION 12-Lead (4mm x 3mm) Plastic DFN 16-Lead Plastic TSSOP 16-Lead Plastic TSSOP TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 140C TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 140C
Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
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LT3012 ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2, 3) Line Regulation Load Regulation (Note 2) Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 250mA VIN = 4V, ILOAD = 1mA 4.75V < VIN < 80V, 1mA < ILOAD < 250mA VIN = 4V to 80V, ILOAD = 1mA (Note 2) VIN = 4.75V, ILOAD = 1mA to 250mA VIN = 4.75V, ILOAD = 1mA to 250mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 250mA ILOAD = 250mA GND Pin Current VIN = 4.75V (Notes 4, 6) Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 8) Quiescent Current in Shutdown Ripple Rejection Current Limit Reverse Output Current (Note 9) ILOAD = 0mA ILOAD = 100mA ILOAD = 250mA COUT = 10F ILOAD = 250mA, BW = 10Hz to 100kHz , (Note 7) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 6V VIN = 6V, VSHDN = 0V VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 250mA VIN = 7V, VOUT = 0V VIN = 4.75V, VOUT = -0.1V (Note 2) VOUT = 1.24V, VIN < 1.24V (Note 2)
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(LT3012E) The l denotes the specifications which apply over the -40C to 125C operating temperature range, otherwise specifications are at TJ = 25C.
MIN 1.225 1.2 TYP 4 1.24 1.24 0.1 7 160 250 400 40 3 10 100 30 0.3 1.3 0.8 0.3 0.1 1 65 250 12 25 75 400 100 2 2 1 5 MAX 4.75 1.255 1.28 5 12 25 230 300 340 420 490 620 100 18 UNITS V V V mV mV mV mV mV mV mV mV mV A mA mA VRMS nA V V A A A dB mA mA A
ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2, 3) Line Regulation Load Regulation (Note 2) Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 200mA
(LT3012H) The l denotes the specifications which apply over the -40C to 140C operating temperature range, otherwise specifications are at TJ = 25C.
MIN
l l l l l l l l l
TYP 4 1.24 1.24 0.1 6 160 250 360 40 3 7
MAX 4.75 1.255 1.28 5 12 30 230 320 340 450 490 630 110 18
UNITS V V V mV mV mV mV mV mV mV mV mV A mA mA
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VIN = 4V, ILOAD = 1mA 4.75V < VIN < 80V, 1mA < ILOAD < 200mA VIN = 4V to 80V, ILOAD = 1mA (Note 2) VIN = 4.75V, ILOAD = 1mA to 200mA VIN = 4.75V, ILOAD = 1mA to 200mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 200mA ILOAD = 200mA
1.225 1.2
GND Pin Current VIN = 4.75V (Notes 4, 6)
ILOAD = 0mA ILOAD = 100mA ILOAD = 200mA
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LT3012 ELECTRICAL CHARACTERISTICS
PARAMETER Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 8) Quiescent Current in Shutdown Ripple Rejection Current Limit Reverse Output Current (Note 9) CONDITIONS COUT = 10F, ILOAD = 200mA, BW = 10Hz to 100kHz (Note 7) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 6V VIN = 6V, VSHDN = 0V VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 200mA VIN = 7V, VOUT = 0V VIN = 4.75V, VOUT = -0.1V (Note 2) VOUT = 1.24V, VIN < 1.24V (Note 2)
l l l
(LT3012H) The l denotes the specifications which apply over the -40C to 140C operating temperature range, otherwise specifications are at TJ = 25C.
MIN TYP 100 30 0.3 1.3 0.8 0.3 0.1 1 65 200 12 25 75 400 100 2 2 1 5 MAX UNITS VRMS nA V V A A A dB mA mA A
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3012 is tested and specified for these conditions with the ADJ pin connected to the OUT pin. Note 3: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current, the input voltage range must be limited. Note 4: To satisfy requirements for minimum input voltage, the LT3012 is tested and specified for these conditions with an external resistor divider (249k bottom, 649k top) for an output voltage of 4.5V. The external resistor divider will add a 5A DC load on the output. Note 5: Dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified output current. In dropout, the output voltage will be equal to (VIN - VDROPOUT).
Note 6: GND pin current is tested with VIN = 4.75V and a current source load. This means the device is tested while operating close to its dropout region. This is the worst-case GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 7: ADJ pin bias current flows into the ADJ pin. Note 8: SHDN pin current flows out of the SHDN pin. Note 9: Reverse output current is tested with the IN pin grounded and the OUT pin forced to the rated output voltage. This current flows into the OUT pin and out the GND pin. Note 10: The LT3012E is guaranteed to meet performance specifications from 0C to 125C operating junction temperature. Specifications over the -40C to 125C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3012H is tested to the LT3012H Electrical Characteristics table at 140C operating junction temperature. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125C. Note 11: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C (LT3012E) or 140C (LT3012H) when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability.
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LT3012 TYPICAL PERFORMANCE CHARACTERISTICS
Typical Dropout Voltage
600 GUARANTEED DROPOUT VOLTAGE (mV) 500 DROPOUT VOLTAGE (mV) 400 300 200 100 0 TJ = 25C TJ = 125C 600 500 DROPOUT VOLTAGE (mV) 400 300 200 100 0 0 50 100 150 200 OUTPUT CURRENT (mA) 250
3012 G01
Guaranteed Dropout Voltage
= TEST POINTS 600 TJ 125C 500 400 300 200 100
Dropout Voltage
IL = 250mA IL = 100mA
TJ 25C
IL = 50mA IL = 10mA IL = 1mA
0
50
150 100 200 OUTPUT CURRENT (mA)
250
3012 G02
0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
3012 G03
Quiescent Current
100 VIN = 6V 90 RL = I =0 80 L 70 60 50 40 30 20 10 0 -50 -25 0 VSHDN = GND 25 50 75 100 125 150 TEMPERATURE (C)
3012 G04
ADJ Pin Voltage
1.260 1.255 ADJ PIN VOLTAGE (V) 1.250 1.245 1.240 1.235 1.230 1.225 1.220 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3012 G05
Quiescent Current
80 70 QUIESCENT CURRENT (A) 60 50 40 30 20 10 VSHDN = GND 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 VSHDN = VIN TJ = 25C RL = VOUT = 1.24V
IL = 1mA
QUIESCENT CURRENT (A)
VSHDN = VIN
3012 G06
Quiescent Current
250 TJ = 25C 225 RL = VOUT = 1.24V 200 GND PIN CURRENT (mA) 175 150 125 100 75 50 25 0 0 10 20 30 40 50 60 INPUT VOLTAGE (V) 70 80 0 VSHDN = GND VSHDN = VIN 1.2 1.0 0.8 0.6 0.4 0.2
GND Pin Current
TJ = 25C *FOR VOUT = 1.24V GND PIN CURRENT (mA) RL = 49.6 IL = 25mA* RL = 124 IL = 10mA* 10 9 8 7 6 5 4 3 2 1 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 0
GND Pin Current
TJ = 25C, *FOR VOUT = 1.24V
QUIESCENT CURRENT(A)
RL = 4.96 IL = 250mA*
RL = 12.4 IL = 100mA*
RL = 1.24k IL = 1mA*
RL = 24.8, IL = 50mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
3012 G07
3012 G08
3012 G09
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LT3012 TYPICAL PERFORMANCE CHARACTERISTICS
GND Pin Current vs ILOAD
10 VIN = 4.75V 9 TJ = 25C = 1.24V V 8 OUT 7 6 5 4 3 2 1 0 0 50 100 150 200 LOAD CURRENT (mA) 250
3012 G10
SHDN Pin Threshold
2.0 1.8 SHDN PIN THRESHOLD (V) SHDN PIN CURRENT (A) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -50 -25 0 0 25 50 75 100 125 150 TEMPERATURE (C)
3012 G11
SHDN Pin Current
0.6 TJ = 25C CURRENT FLOWS 0.5 OUT OF SHDN PIN
GND PIN CURRENT (mA)
OFF-TO-ON
0.4 0.3 0.2 0.1
ON-TO-OFF
0
0.5
1.0 2.0 1.5 2.5 SHDN PIN VOLTAGE (V)
3.0
3012 G12
SHDN Pin Current
0.6 VIN = 6V VSHDN = 0V 0.5 CURRENT FLOWS OUT OF SHDN PIN 0.4 0.3 0.2 0.1 0 -50 -25 120 100
ADJ Pin Bias Current
1000 900 ADJ PIN BIAS CURRENT (nA) 800 CURRENT LIMIT (mA) 700 600 500 400 300 200 100
Current Limit
VOUT = 0V
SHDN PIN CURRENT (A)
80 60 40 20 0 -50 -25
TJ = 25C TJ = 125C
0
25 50 75 100 125 150 TEMPERATURE (C)
3012 G13
0
25 50 75 100 125 150 TEMPERATURE (C)
3012 G14
0
0
10
20
30 40 50 60 INPUT VOLTAGE (V)
70
80
3012 G15
Current Limit
700 REVERSE OUTPUT CURRENT (A) 600 CURRENT LIMIT (mA) 500 400 300 200 100 VIN = 7V VOUT = 0V 0 25 50 75 100 125 150 TEMPERATURE (C)
3012 G16
Reverse Output Current
200 REVERSE OUTPUT CURRENT (A) TJ = 25C 180 VIN = 0V VOUT = VADJ 160 140 120 100 CURRENT FLOWS 80 INTO OUTPUT PIN 60 40 20 0 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10 ADJ PIN CLAMP (SEE APPLICATIONS INFORMATION) 120 100 80 60 40 20
Reverse Output Current
VIN = 0V VOUT = VADJ = 1.24V
0 -50 -25
0 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
3012 G18
3012 G17
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LT3012 TYPICAL PERFORMANCE CHARACTERISTICS
Input Ripple Rejection
92 88 RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) 84 80 76 72 68 64 60 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3012 G19
Input Ripple Rejection
100 90 80 70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M
3012 G20
Minimum Input Voltage
5.0 4.5 MINIMUM INPUT VOLTAGE (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3012 G21
VIN = 4.75V + 50mVRMS RIPPLE ILOAD = 250mA
ILOAD = 250mA
COUT = 10F
VIN = 4.75V + 0.5VP-P RIPPLE AT f = 120Hz IL = 250mA VOUT = 1.24V
COUT = 3.3F
Load Regulation
OUTPUT NOISE SPECTRAL DENSITY (V/Hz) 0 -2 LOAD REGULATION (mV) -4 -6 -8 -10 -12 -14 -16 -18 -20 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
3012 G22
Output Noise Spectral Density
10 COUT = 3.3F ILOAD = 250mA
IL = 1mA TO 250mA
1
0.1
0.01 10 100 1k 10k FREQUENCY (Hz) 100k
3012 G23
10Hz to 100kHz Output Noise
0.15 OUTPUT VOLTAGE DEVIATION (V) 0.10 0.05 0 -0.05 -0.10 -0.15 300 200 100 0
Transient Response
VOUT 100V/DIV
COUT = 10F IL = 250mA VOUT = 1.24V
1ms/DIV
3012 G24
LOAD CURRENT (mA)
VIN = 6V VOUT = 5V CIN = 3.3F CERAMIC COUT = 3.3F CERAMIC ILOAD = 100mA TO 200mA
0
100
300 200 TIME (s)
400
500
3012 G25
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LT3012 PIN FUNCTIONS
(DFN Package/TSSOP Package)
NC (Pins 1, 6, 7, 9, 12)/(Pins 2, 7, 10, 12, 15): No Connect. These pins have no internal connection; connecting NC pins to a copper area for heat dissipation provides a small improvement in thermal performance. OUT (Pins 2, 3)/(Pins 3, 4): Output.The output supplies power to the load. A minimum output capacitor of 3.3F is required to prevent oscillations. Larger output capacitors will be required for applications with large transient loads to limit peak voltage transients. See the Applications Information section for more information on output capacitance and reverse output characteristics. ADJ (Pin 4)/(Pin 5): Adjust. This is the input to the error amplifier. This pin is internally clamped to 7V. It has a bias current of 30nA which flows into the pin (see curve of ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics). The ADJ pin voltage is 1.24V referenced to ground, and the output voltage range is 1.24V to 60V. GND (Pins 5, 13)/(Pins 1, 6, 8, 9, 16, 17): Ground. The exposed backside of the package is an electrical connection for GND. As such, to ensure optimum device operation and thermal performance, the exposed pad must be connected directly to pin 5/pin 6 on the PC board.
SHDN (Pin 8)/(Pin 11): Shutdown. The SHDN pin is used to put the LT3012 into a low power shutdown state. The output will be off when the SHDN pin is pulled low. The SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor. The pull-up resistor is only required to supply the pull-up current of the open-collector gate, normally several microamperes. If unused, the SHDN pin must be tied to a logic high or to VIN. IN (Pins 10, 11)/(Pins 13,14): Input. Power is supplied to the device through the IN pin. A bypass capacitor is required on this pin if the device is more than six inches away from the main input filter capacitor. In general, the output impedance of a battery rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 1F to 10F is sufficient. The LT3012 is designed to withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reversed input, which can happen if a battery is plugged in backwards, the LT3012 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT3012 and no reverse voltage will appear at the load. The device will protect both itself and the load.
APPLICATIONS INFORMATION
The LT3012 is a 250mA high voltage low dropout regulator with micropower quiescent current and shutdown. The device is capable of supplying 250mA at a dropout voltage of 400mV. The low operating quiescent current (40A) drops to 1A in shutdown. In addition to the low quiescent current, the LT3012 incorporates several protection features which make it ideal for use in battery-powered systems. The device is protected against both reverse input and reverse output voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT3012 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The LT3012 has an output voltage range of 1.24V to 60V. The output voltage is set by the ratio of two external resistors as shown in Figure 1. The device servos the output to maintain the voltage at the adjust pin at 1.24V referenced to ground. The current in R1 is then equal to 1.24V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current. The ADJ pin bias current, 30nA at 25C, flows through R2 into the ADJ pin. The output voltage can be calculated using the formula in Figure 1. The value of R1 should be less than 250k to minimize errors in the output voltage caused by the ADJ pin bias current. Note that in shutdown the output is turned off and the divider current will be zero.
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LT3012 APPLICATIONS INFORMATION
IN VIN OUT LT3012 ADJ GND R1
3012 F01
R2
+
VOUT
improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT3012, will increase the effective output capacitor value. Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are specified with EIA temperature characteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but they tend to have strong voltage and temperature coefficients as shown in Figures 2 and 3. When used with a 5V regulator, a 16V 10F Y5V capacitor can exhibit an effective value as low as 1F to 2F for the DC bias voltage applied and over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values. Care still must be exercised when using X5R and X7R capacitors; the X5R and X7R codes only specify operating temperature range and maximum capacitance change over temperature. Capacitance change due to DC bias with X5R and X7R capacitors is better than Y5V and Z5U capacitors, but can still be significant enough to drop capacitor values below appropriate levels. Capacitor DC bias characteristics tend to improve as component case size increases, but expected capacitance at operating voltage should be verified.
40 20 CHANGE IN VALUE (%) 0 X5R -20 -40 -60 -80 Y5V
VOUT = 1.24V 1 + R2 + (IADJ)(R2) R1 VADJ = 1.24V IADJ = 30nA AT 25C OUTPUT RANGE = 1.24V TO 60V
Figure 1. Adjustable Operation
The adjustable device is tested and specified with the ADJ pin tied to the OUT pin and a 5A DC load (unless otherwise specified) for an output voltage of 1.24V. Specifications for output voltages greater than 1.24V will be proportional to the ratio of the desired output voltage to 1.24V; (VOUT /1.24V). For example, load regulation for an output current change of 1mA to 250mA is -7mV typical at VOUT = 1.24V. At VOUT = 12V, load regulation is: (12V/1.24V) * (-7mV) = -68mV Output Capacitance and Transient Response The LT3012 is designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 3.3F with an ESR of 3 or less is recommended to prevent oscillations. The LT3012 is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide
20 0 CHANGE IN VALUE (%) X5R -20 -40 -60 Y5V -80 -100 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
14
16
3012 F02
BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F -100 50 25 75 -50 -25 0 TEMPERATURE (C)
100
125
3012 F03
Figure 2. Ceramic Capacitor DC Bias Characteristics
Figure 3. Ceramic Capacitor Temperature Characteristics
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LT3012 APPLICATIONS INFORMATION
Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. Current Limit and Safe Operating Area Protection Like many IC power regulators, the LT3012 has safe operating area protection. The safe operating area protection decreases the current limit as the input voltage increases and keeps the power transistor in a safe operating region. The protection is designed to provide some output current at all values of input voltage up to the device breakdown (see curve of Current Limit vs Input Voltage in the Typical Performance Characteristics). The LT3012 is limited for operating conditions by maximum junction temperature. While operating at maximum input voltage, the output current range must be limited; when operating at maximum output current, the input voltage range must be limited. Device specifications will not apply for all possible combinations of input voltage and output current. Operating the LT3012 beyond the maximum junction temperature rating may impair the life of the device. Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature of (125C for LT3012E, or 140C for LT3012HFE). The power dissipated by the device will be made up of two components: 1. Output current multiplied by the input/output voltage differential: IOUT * (VIN - VOUT) and, 2. GND pin current multiplied by the input voltage: IGND * VIN. The GND pin current can be found by examining the GND Pin Current curves in the Typical Performance Characteristics. Power dissipation will be equal to the sum of the two components listed above. The LT3012 has internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions the maximum junction temperature rating of 125C (E-Grade) or 140C (H-Grade)must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices. The following tables list thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with one ounce copper.
Table 1. DFN Measured Thermal Resistance
COPPER AREA TOPSIDE 2500 sq mm 1000 sq mm 225 sq mm 100 sq mm BOARD AREA 2500 sq mm 2500 sq mm 2500 sq mm 2500 sq mm THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 40C/W 45C/W 50C/W 62C/W
Table 2. TSSOP Measured Thermal Resistance
COPPER AREA TOPSIDE 2500 sq mm 1000 sq mm 225 sq mm 100 sq mm BOARD AREA 2500 sq mm 2500 sq mm 2500 sq mm 2500 sq mm THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 40C/W 45C/W 50C/W 62C/W
The thermal resistance junction-to-case (JC), measured at the exposed pad on the back of the die, is 16C/W. Continuous operation at large input/output voltage differentials and maximum load current is not practical due to thermal limitations. Transient operation at high input/output differentials is possible. The approximate thermal time constant for a 2500sq mm 3/32" FR-4 board with maximum topside and backside area for one ounce copper is 3 seconds. This time constant will increase as more thermal mass is added (i.e., vias, larger board, and other components).
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LT3012 APPLICATIONS INFORMATION
For an application with transient high power peaks, average power dissipation can be used for junction temperature calculations as long as the pulse period is significantly less than the thermal time constant of the device and board. Calculating Junction Temperature Example 1: Given an output voltage of 5V, an input voltage range of 24V to 30V, an output current range of 0mA to 50mA, and a maximum ambient temperature of 50C, what will the maximum junction temperature be? The power dissipated by the device will be equal to: IOUT(MAX) * (VIN(MAX) - VOUT) + (IGND * VIN(MAX)) where: IOUT(MAX) = 50mA VIN(MAX) = 30V IGND at (IOUT = 50mA, VIN = 30V) = 1mA So: P = 50mA * (30V - 5V) + (1mA * 30V) = 1.28W The thermal resistance will be in the range of 40C/W to 62C/W depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: 1.31W * 50C/W = 65.5C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50C + 65.5C = 115.5C Example 2: Given an output voltage of 5V, an input voltage of 48V that rises to 72V for 5ms(max) out of every 100ms, and a 5mA load that steps to 50mA for 50ms out of every 250ms, what is the junction temperature rise above ambient? Using a 500ms period (well under the time constant of the board), power dissipation is as follows: P1(48V in, 5mA load) = 5mA * (48V - 5V) + (200A * 48V) = 0.23W P2(48V in, 50mA load) = 50mA * (48V - 5V) + (1mA * 48V) = 2.20W
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P3(72V in, 5mA load) = 5mA * (72V - 5V) + (200A * 72V) = 0.35W P4(72V in, 50mA load) = 50mA * (72V - 5V) + (1mA * 72V) = 3.42W Operation at the different power levels is as follows: 76% operation at P1, 19% for P2, 4% for P3, and 1% for P4. PEFF = 76%(0.23W) + 19%(2.20W) + 4%(0.35W) + 1%(3.42W) = 0.64W With a thermal resistance in the range of 40C/W to 62C/W, this translates to a junction temperature rise above ambient of 26C to 38C. High Temperature Operation Care must be taken when designing LT3012 applications to operate at high ambient temperatures. The LT3012 works at elevated temperatures but erratic operation can occur due to unforeseen variations in external components. Some tantalum capacitors are available for high temperature operation, but ESR is often several ohms; capacitor ESR above 3 is unsuitable for use with the LT3012. Ceramic capacitor manufacturers (Murata, AVX, TDK, and Vishay Vitramon at this writing) now offer ceramic capacitors that are rated to 150C using an X8R dielectric. Device instability will occur if output capacitor value and ESR are outside design limits at elevated temperature and operating DC voltage bias (see information on capacitor characteristics under Output Capacitance and Transient Response). Check each passive component for absolute value and voltage ratings over the operating temperature range. Leakages in capacitors or from solder flux left after insuficient board cleaning adversely affects low quiescent current operation. The output voltage resistor divider should use a maximum bottom resistor value of 124k to compensate for high temperature leakage, setting divider current to 10A. Consider junction temperature increase due to power dissipation in both the junction and nearby components to ensure maximum specifications are not violated for the device or external components.
11
LT3012 APPLICATIONS INFORMATION
Protection Features The LT3012 incorporates several protection features which make it ideal for use in battery-powered circuits. In addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting, the device is protected against reverse-input voltages, and reverse voltages from output to input. Like many IC power regulators, the LT3012 has safe operating area protection. The safe area protection decreases the current limit as input voltage increases and keeps the power transistor inside a safe operating region for all values of input voltage. The protection is designed to provide some output current at all values of input voltage up to the device breakdown. The SOA protection circuitry for the LT3012 uses a current generated when the input voltage exceeds 25V to decrease current limit. This current shows up as additional quiescent current for input voltages above 25V. This increase in quiescent current occurs both in normal operation and in shutdown (see curve of Quiescent Current in the Typical Performance Characteristics). Current limit protection and thermal overload protection are intended to protect the device against current overload conditions at the output of the device. For normal operation, the junction temperature should not exceed 125C (LT3012E) or 140C (LT3012HFE). The input of the device will withstand reverse voltages of 80V. No negative voltage will appear at the output. The device will protect both itself and the load. This provides protection against batteries which can be plugged in backward. The ADJ pin of the device can be pulled above or below ground by as much as 7V without damaging the device. If the input is left open circuit or grounded, the ADJ pin will act like an open circuit when pulled below ground, and like a large resistor (typically 100k) in series with a diode when pulled above ground. If the input is powered by a voltage source, pulling the ADJ pin below the reference voltage will cause the device to current limit. This will cause the output to go to a unregulated high voltage. Pulling the ADJ pin above the reference voltage will turn off all output current. In situations where the ADJ pin is connected to a resistor divider that would pull the ADJ pin above its 7V clamp voltage if the output is pulled high, the ADJ pin input current must be limited to less than 5mA. For example, a resistor divider is used to provide a regulated 1.5V output from the 1.24V reference when the output is forced to 60V. The top resistor of the resistor divider must be chosen to limit the current into the ADJ pin to less than 5mA when the ADJ pin is at 7V. The 53V difference between the OUT and ADJ pins divided by the 5mA maximum current into the ADJ pin yields a minimum top resistor value of 10.6k. In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage, or is left open circuit. Current flow back into the output will follow the curve shown in Figure 4. The rise in reverse output current above 7V occurs from the breakdown of the 7V clamp on the ADJ pin. With a resistor divider on the regulator output, this current will be reduced depending on the size of the resistor divider.
200 REVERSE OUTPUT CURRENT (A) TJ = 25C 180 VIN = 0V VOUT = VADJ 160 140 120 100 CURRENT FLOWS 80 INTO OUTPUT PIN 60 40 20 0 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10 ADJ PIN CLAMP (SEE ABOVE)
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Figure 4. Reverse Output Current
When the IN pin of the LT3012 is forced below the OUT pin or the OUT pin is pulled above the IN pin, input current will typically drop to less than 2A. This can happen if the input of the LT3012 is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or a second regulator circuit. The state of the SHDN pin will have no effect on the reverse output current when the output is pulled above the input.
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12
LT3012 TYPICAL APPLICATIONS
5V Buck Converter with Low Current Keep Alive Backup
D2 D1N914 6 VIN 5.5V* TO 60V 4 C3 4.7F 100V CERAMIC BOOST VIN LT1766 15 14 SHDN SYNC GND BIAS FB VC CC 1nF 10 12 R1 15.4k R2 4.99k SW 2 C2 0.33F
L1 15H
D1 10MQ060N
VOUT 5V 1A/250mA
+
C1 100F 10V SOLID TANTALUM
1, 8, 9, 16 11
14 OPERATING CURRENT LOW HIGH 11
IN LT3012 SHDN GND 1
OUT ADJ
3 5 750k * FOR INPUT VOLTAGES BELOW 7.5V, SOME RESTRICTIONS MAY APPLY INCREASE L1 TO 30H FOR LOAD CURRENTS ABOVE 0.6A AND TO 60H ABOVE 1A
3012 TA03
249k
Buck Converter Efficiency vs Load Current
100 VOUT = 5V L = 68H VIN = 10V
90 EFFICIENCY (%) VIN = 42V 80
70
60
50
0
0.25
0.75 1.00 0.50 LOAD CURRENT (A)
1.25
3012 TA04
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13
LT3012 TYPICAL APPLICATIONS
LT3012 Automotive Application
VIN 12V (LATER 42V)
+
1F
IN NO PROTECTION DIODE NEEDED! LT3012 SHDN GND
OUT 750k ADJ 249k 3.3F LOAD: CLOCK, SECURITY SYSTEM ETC
OFF ON
LT3012 Telecom Application
VIN 48V (72V TRANSIENT) 1F
IN LT3012 SHDN GND
OUT 750k NO PROTECTION DIODE NEEDED! 249k
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+
3.3F LOAD: SYSTEM MONITOR ETC
ADJ
-
BACKUP BATTERY
OFF ON
Constant Brightness for Indicator LED over Wide Input Voltage Range
RETURN 1F OFF ON IN OUT LT3012 SHDN GND -48V ILED = 1.24V/RSET -48V CAN VARY FROM -4V TO -80V ADJ RSET
3012 TA06
3.3F
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14
LT3012 PACKAGE DESCRIPTION
DE Package 12-Lead Plastic DFN (4mm x 3mm)
(Reference LTC DWG # 05-08-1695)
4.00 0.10 (2 SIDES) 0.70 0.05 3.30 0.05 1.70 0.05 PIN 1 TOP MARK PACKAGE (NOTE 6) OUTLINE 0.200 REF R = 0.05 TYP 3.00 0.10 (2 SIDES) 3.30 0.10 1.70 0.10 PIN 1 NOTCH R = 0.20 OR 0.35 x 45 CHAMFER
(UE12/DE12) DFN 0806 REV D
7
R = 0.115 TYP
0.40 0.10 12
3.60 0.05 2.20 0.05
0.25 0.05 2.50 REF
0.75 0.05
6 0.25 0.05 2.50 REF
1 0.50 BSC
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING PROPOSED TO BE A VARIATION OF VERSION (WGED) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
FE Package 16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BB
3.58 (.141) 4.90 - 5.10* (.193 - .201) 3.58 (.141) 16 1514 13 12 1110 9
6.60 0.10 4.50 0.10
SEE NOTE 4
2.94 (.116) 0.45 0.05 1.05 0.10 0.65 BSC 2.94 6.40 (.116) (.252) BSC
RECOMMENDED SOLDER PAD LAYOUT
12345678 1.10 (.0433) MAX
0 - 8
4.30 - 4.50* (.169 - .177)
0.25 REF
0.09 - 0.20 (.0035 - .0079)
0.50 - 0.75 (.020 - .030)
0.65 (.0256) BSC
NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE
0.195 - 0.30 (.0077 - .0118) TYP
0.05 - 0.15 (.002 - .006)
FE16 (BB) TSSOP 0204
4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LT3012 RELATED PARTS
PART NUMBER LT1020 LT1120/LT1120A DESCRIPTION COMMENTS 125mA, Micropower Regulator and Comparator VIN: 4.5V to 36V, VOUT(MIN) = 2.5V, VDO = 0.4V, IQ = 40A, ISD = 40A, Comparator and Reference, Class B Outputs, S16, PDIP14 Packages 125mA, Micropower Regulator and Comparator VIN: 4.5V to 36V, VOUT(MIN) = 2.5V, VDO = 0.4V, IQ = 40A, ISD = 10A, Comparator and Reference, Logic Shutdown, Ref Sources and Sinks 2/4mA, S8, N8 Packages 150mA, Micropower, LDO 700mA, Micropower, LDO 60V, 440mA (IOUT), 100kHz, High Efficiency Step-Down DC/DC Converter 100mA, Low Noise Micropower, LDO 150mA, Low Noise Micropower, LDO 500mA, Low Noise Micropower, LDO 3A, Low Noise, Fast Transient Response, LDO VIN: 4.2V to 30/36V, VOUT(MIN) = 3.75V, VDO = 0.42V, IQ = 30A, ISD = 16A, Reverse Battery Protection, SOT-223, S8, Z Packages VIN: 4.2V to 30V, VOUT(MIN) = 3.75V, VDO = 0.4V, IQ = 50A, ISD = 16A, DD, S0T-223, S8,TO220-5, TSSOP20 Packages VIN: 7.4V to 60V, VOUT(MIN) = 1.24V, IQ = 3.2mA, ISD = 2.5A, S8 Package VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.3V, IQ = 20A, ISD = <1A, Low Noise < 20VRMS, Stable with 1F Ceramic Capacitors, ThinSOTTM Package VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.3V, IQ = 25A, ISD = <1A, Low Noise < 20VRMS, MS8 Package VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.3V, IQ = 30A, ISD = <1A, Low Noise < 20VRMS, S8 Package VIN: 2.7V to 20V, VOUT(MIN) = 1.21V, VDO = 0.34V, IQ = 1mA, ISD = <1A, Low Noise < 40VRMS, "A" Version Stable with Ceramic Capacitors, DD, TO220-5 Packages VIN: 5.5V to 60V, VOUT(MIN) = 1.2V, IQ = 2.5mA, ISD = 25A, TSSOP16/E Package VIN: 7.4V to 40V, VOUT(MIN) = 1.24V, IQ = 3.2mA, ISD = 30A, N8, S8 Packages 90% Efficiency, VIN: 3.2V to 34V, VOUT(MIN) = 1.25V, IQ = 14A, ISD = <1A, ThinSOT Package VIN: 5.5V to 60V, VOUT(MIN) = 1.2V, IQ = 2.5mA, ISD = 25A, TSSOP16/E Package VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.27V, IQ = 30A, ISD = <1A, Low Noise < 20VRMS, MS8 Package VIN: 2.1V to 20V, VOUT(MIN) = 1.21V, VDO = 0.34V, IQ = 1mA, ISD = <1A, Low Noise < 40VRMS, "A" Version Stable with Ceramic Capacitors, DD, TO220-5, S0T-223, S8 Packages VIN: -1.9V to -20V, VOUT(MIN) = -1.21V, VDO = 0.34V, IQ = 30A, ISD = 3A, Low Noise < 30VRMS, Stable with Ceramic Capacitors, ThinSOT Package VIN: 3V to 8V, VOUT(MIN) = 1.275V, VDO = 0.3V, IQ = 30A, ISD = 1A, Low Noise < 100VRMS, MS8E Package, H Grade = +140C TJMAX. VIN: 4V to 80V, VOUT: 1.24V to 60V, VDO = 0.4V, IQ = 65A, ISD = <1A, Power Good Feature; TSSOP-16E and 4mm x 3mm DFN-12 Packages, H Grade = +140C TJMAX. VIN: 3V to 80V (100V for 2ms, HV version), VOUT: 1.22V to 60V, VDO = 0.35V, IQ = 7A, ISD = <1A, ThinSOT and 3mm x 3mm DFN-8 Packages.
LT1121/LT1121HV LT1129 LT1676 LT1761 LT1762 LT1763 LT1764/LT1764A
LT1766 LT1776 LT1934/LT1934-1 LT1956 LT1962 LT1963/LT1963A
60V, 1.2A (IOUT), 200kHz, High Efficiency Step-Down DC/DC Converter 40V, 550mA (IOUT), 200kHz, High Efficiency Step-Down DC/DC Converter 300mA/60mA, (IOUT), Constant Off-Time, High Efficiency Step-Down DC/DC Converter 60V, 1.2A (IOUT), 500kHz, High Efficiency Step-Down DC/DC Converter 300mA, Low Noise Micropower, LDO 1.5A, Low Noise, Fast Transient Response, LDO
LT1964 LT3010/LT3010H LT3013/LT3013H
200mA, Low Noise Micropower, Negative LDO 50mA, 3V to 80V, Low Noise Micropower LDO 250mA, 4V to 80V, Low Dropout Micropower Linear Regulator with PWRGD 20mA, 3V to 80V, Low Dropout Micropower Linear Regulator
LT3014/HV
ThinSOT is a trademark of Linear Technology Corporation.
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16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0508 REV D * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005

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