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LT3012B 250mA, 4V to 80V Low Dropout Micropower Linear Regulator
FEATURES

DESCRIPTIO
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 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
The LT(R)3012B 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) makes the LT3012B an ideal choice. Quiescent current is also well controlled in dropout. Other features of the LT3012B include the ability to operate with very small output capacitors. The regulators are 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 LT3012B 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.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
APPLICATIO S

Low Current High Voltage Regulators Regulator for Battery-Powered Systems Telecom Applications Automotive Applications
TYPICAL APPLICATIO
5V Supply
400 350
DROPOUT VOLTAGE (mV)
VOUT 5V 250mA 3.3F
300 250 200 150 100 50 0 0 50 100 150 200 OUTPUT CURRENT (mA) 250
IN VIN 5.4V TO 80V 1F
OUT LT3012B ADJ GND 249k
3012B TA01
750k
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Dropout Voltage
3012B TA02
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LT3012B
ABSOLUTE
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RATI GS (Note 1)
Storage Temperature Range TSSOP Package ........................... -65C to 150C DFN Package ............................... -65C to 125C Operating Junction Temperature Range (Notes 3, 9, 10) ........................... -40C to 125C Lead Temperature (Soldering, 10 sec)............ 300C
IN Pin Voltage ................................................... 80V OUT Pin Voltage ............................................... 60V IN to OUT Differential Voltage ........................... 80V ADJ Pin Voltage .................................................. 7V Output Short-Circuit Duration ..................... Indefinite
PACKAGE/ORDER I FOR ATIO
TOP VIEW NC OUT OUT ADJ GND NC 1 2 3 13 4 5 6 9 8 7 NC NC NC 12 NC 11 IN 10 IN
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
ORDER PART NUMBER LT3012BEDE
DE PART MARKING 3012B
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25C.
PARAMETER Minimum Input Voltage ADJ Pin Voltage (Notes 2, 3) Line Regulation Load Regulation (Note 2) CONDITIONS ILOAD = 250mA VIN = 4V, ILOAD = 1mA 4.5V < VIN < 80V, 1mA < ILOAD < 250mA VIN = 4V to 80V, ILOAD = 1mA (Note 2) VIN = 4.5V, ILOAD = 1mA to 250mA VIN = 4.5V, ILOAD = 1mA to 250mA
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TOP VIEW GND NC OUT OUT ADJ GND NC GND 1 2 3 4 5 6 7 8 17 16 GND 15 NC 14 IN 13 IN 12 NC 11 NC 10 NC 9 GND
FE PACKAGE 16-LEAD PLASTIC TSSOP
TJMAX = 125C, JA = 40C/ W, JC = 16C/ W EXPOSED PAD (PIN 17) IS GND MUST BE SOLDERED TO PCB
ORDER PART NUMBER LT3012BEFE
FE PART MARKING 3012BEFE
MIN 1.225 1.2

TYP 4 1.24 1.24 0.1 7
MAX 4.5 1.255 1.28 5 12 25
UNITS V V V mV mV mV
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LT3012B
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25C.
PARAMETER Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) CONDITIONS ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 250mA ILOAD = 250mA GND Pin Current VIN = 4.5V (Notes 4, 6) Output Voltage Noise ADJ Pin Bias Current Ripple Rejection Current Limit Reverse Output Current (Note 8) ILOAD = 0mA ILOAD = 100mA ILOAD = 250mA COUT = 10F, ILOAD = 250mA, BW = 10Hz to 100kHz (Note 7) VIN = 7V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 250mA VIN = 7V, VOUT = 0V VIN = 4.5V, VOUT = -0.1V (Note 2) VOUT = 1.24V, VIN < 1.24V (Note 2) 65 270 12 25
MIN
TYP 160 250
MAX 230 300 340 420 490 620 100 18 100
UNITS mV mV mV mV mV mV A mA mA VRMS nA dB mA mA A
400

40 3 10 100 30 75 400
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 LT3012B 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 LT3012B is tested and specified for these conditions with an external resistor divider (249k bottom, 549k top) for an output voltage of 4V. 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 = 4.5V 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: 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 9: The LT3012BE 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. Note 10: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability.
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LT3012B TYPICAL PERFOR A CE CHARACTERISTICS
Typical Dropout Voltage
600
GUARANTEED DROPOUT VOLTAGE (mV)
500
DROPOUT VOLTAGE (mV)
TJ = 125C
DROPOUT VOLTAGE (mV)
400 300 200 100 0 TJ = 25C
0
50
100 150 200 OUTPUT CURRENT (mA)
Quiescent Current
100
VIN = 6V 90 RL = I =0 80 L 70 60 50
ADJ PIN VOLTAGE (V)
QUIESCENT CURRENT (A)
1.250 1.245 1.240 1.235 1.230 1.225
QUIESCENT CURRENT (A)
40
30 20 10 0 - 50 - 25 0 50 75 25 TEMPERATURE (C) 100 125
GND Pin Current
1.2 1.0 TJ = 25C *FOR VOUT = 1.24V
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
0.8 0.6 0.4 0.2 0
7 6 5 4 3 2 1
GND PIN CURRENT (mA)
RL = 49.6 IL = 25mA* RL = 124 IL = 10mA*
RL = 1.24k IL = 1mA*
0
1
2
34567 INPUT VOLTAGE (V)
4
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3012B G01
3012B G04
Guaranteed Dropout Voltage
600 500 400 300 200 100 0 = TEST POINTS TJ 125C
Dropout Voltage
600 500 400 300 IL = 50mA 200 IL = 10mA 100 0 -50 -25 IL = 1mA 50 25 0 75 TEMPERATURE (C) 100 125 IL = 250mA IL = 100mA
TJ 25C
250
0
50
150 100 200 OUTPUT CURRENT (mA)
250
301B2 G02
3012B G03
ADJ Pin Voltage
1.260 1.255 IL = 1mA 80 70 60 50 40 30 20 10 0 50 75 25 TEMPERATURE (C) 100 125 0
Quiescent Current
TJ = 25C RL = VOUT = 1.24V
1.220 - 50 - 25
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
3012B G05
3012B G06
GND Pin Current
10 9 8 RL = 4.96 IL = 250mA* TJ = 25C, *FOR VOUT = 1.24V 10
GND Pin Current vs ILOAD
VIN = 4.5V 9 TJ = 25C = 1.24V V 8 OUT 7 6 5 4 3 2
RL = 12.4 IL = 100mA*
RL = 24.8, IL = 50mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1 0 0 50 100 150 200 LOAD CURRENT (mA) 250
3012B G09
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9
10
0
3012B G07
3012B G08
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LT3012B TYPICAL PERFOR A CE CHARACTERISTICS
ADJ Pin Bias Current
50 45
ADJ PIN BIAS CURRENT (nA)
40 35 30 25 20 15 10 5 0 - 50 - 25 0 50 75 25 TEMPERATURE (C) 100 125
CURRENT LIMIT (mA)
700 600 500 400 300 200 100 0 0 10 20 TJ = 125C
TJ = 25C
CURRENT LIMIT (mA)
Reverse Output Current
200
REVERSE OUTPUT CURRENT (A)
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)
25 20 15 10 5 0 - 50 - 25
RIPPLE REJECTION (dB)
Input Ripple Rejection
100 VIN = 4.5V + 50mVRMS RIPPLE 90 ILOAD = 250mA
MINIMUM INPUT VOLTAGE (V)
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5
80
RIPPLE REJECTION (dB)
70 60 50 40 30 20 10 0 10 100 1k 10k FREQUENCY (Hz) 100k 1M
3012B G19
UW
3012B G13
3012B G16
Current Limit
1000 900 800 VOUT = 0V
Current Limit
700 600 500 400 300 200 100 VIN = 7V VOUT = 0V 50 25 0 75 TEMPERATURE (C) 100 125
30 40 50 60 INPUT VOLTAGE (V)
70
80
0 -50 -25
3012B G14
3012B G15
Reverse Output Current
35 30 VIN = 0V VOUT = VADJ = 1.24V
92 88 84 80 76 72 68 64
Input Ripple Rejection
VIN = 4.5V + 0.5VP-P RIPPLE AT f = 120Hz IL = 250mA VOUT = 1.24V 50 25 0 75 TEMPERATURE (C) 100 125
0
75 50 25 TEMPERATURE (C)
100
125
60 -50 -25
3012B G17
3012B G18
Minimum Input Voltage
ILOAD = 250mA
COUT = 10F
COUT = 3.3F
0 - 50 - 25
0
50 75 25 TEMPERATURE (C)
100
125
3012B G20
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LT3012B TYPICAL PERFOR A CE CHARACTERISTICS
Output Noise Spectral Density
OUTPUT NOISE SPECTRAL DENSITY (V/Hz)
10
COUT = 3.3F ILOAD = 250mA LOAD REGULATION (mV)
1
0.1
0.01 10 100 1k 10k FREQUENCY (Hz) 100k
3012B G22
10Hz to 100kHz Output Noise
0.15
OUTPUT VOLTAGE DEVIATION (V)
VOUT 100V/DIV
LOAD CURRENT (mA)
COUT = 10F IL = 250mA VOUT = 1.24V
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Load Regulation
0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -20 - 50 - 25 0 75 50 25 TEMPERATURE (C) 100 125 IL = 1mA TO 250mA
3012B G21
Transient Response
0.10 0.05 0 -0.05 -0.10 -0.15 300 200 100 0 0 100 300 200 TIME (s) 400 500
3012B G24
VIN = 6V VOUT = 5V CIN = 3.3F CERAMIC COUT = 3.3F CERAMIC ILOAD = 100mA TO 200mA
1ms/DIV
3012B G23
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LT3012B
PI FU CTIO S
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.
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(DFN Package)/(TSSOP Package)
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 batterypowered circuits. A bypass capacitor in the range of 1F to 10F is sufficient. The LT3012B 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 LT3012B will act as if there is a diode in series with its input. There will be no reverse current flow into the LT3012B and no reverse voltage will appear at the load. The device will protect both itself and the load. NC (Pins 1, 6-9, 12)/(Pins 2, 7, 10-12, 15): No Connect. No Connect pins may be floated, tied to IN or tied to GND.
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LT3012B
APPLICATIO S I FOR ATIO
The LT3012B is a 250mA high voltage low dropout regulator with micropower quiescent current. The device is capable of supplying 250mA at a dropout voltage of 400mV. Operating quiescent current is only 40A. In addition to the low quiescent current, the LT3012B 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 LT3012B acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The LT3012B 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. 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
VIN
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
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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 LT3012B 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 LT3012B 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 improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT3012B, 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
IN OUT R2 R1 C1 LT3012B ADJ GND
3012B F01
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VOUT
()
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LT3012B
APPLICATIO S I FOR ATIO
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. 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 LT3012B 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 operat20 0 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F
CHANGE IN VALUE (%)
CHANGE IN VALUE (%)
X5R -20 -40 -60 Y5V -80
-100
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
14
16
3012B F02
Figure 2. Ceramic Capacitor DC Bias Characterics
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ing 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 LT3012B 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 LT3012B 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 (125C). 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.
40 20 0 X5R -20 -40 -60 -80 Y5V BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F -100 50 25 75 -50 -25 0 TEMPERATURE (C) 100 125
3012B F03
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Figure 3. Ceramic Capacitor Temperature Characterics
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LT3012B
APPLICATIO S I FOR ATIO
The LT3012B has internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions the maximum junction temperature rating of 125C 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 BACKSIDE 2500 sq mm 2500 sq mm 2500 sq mm 2500 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 BACKSIDE 2500 sq mm 2500 sq mm 2500 sq mm 2500 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.
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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). 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
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LT3012B
APPLICATIO S I FOR ATIO
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 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.
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Protection Features The LT3012B 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. 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. 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.
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LT3012B
APPLICATIO S I FOR ATIO
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
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)
Figure 4. Reverse Output Current
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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. When the IN pin of the LT3012B 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 LT3012B is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or a second regulator circuit.
3012B F04
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LT3012B
TYPICAL APPLICATIO S
LT3012B Automotive Application
IN 1F
NO PROTECTION DIODE NEEDED!
VIN 12V (LATER 42V)
+
VIN 48V (72V TRANSIENT)
1F
Constant Brightness for Indicator LED over Wide Input Voltage Range
RETURN 1F
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OUT LT3012B ADJ GND
249k
750k
3.3F
LOAD: CLOCK, SECURITY SYSTEM ETC
LT3012B Telecom Application
IN LT3012B
OUT
750k NO PROTECTION DIODE NEEDED!
249k
3012B TA05
+
3.3F
LOAD: SYSTEM MONITOR ETC
ADJ GND
-
BACKUP BATTERY
IN
OUT
LT3012B ADJ GND RSET
3012B TA06
3.3F
-48V ILED = 1.24V/RSET -48V CAN VARY FROM -4V TO -80V
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13
LT3012B
PACKAGE DESCRIPTIO U
DE/UE Package 12-Lead Plastic DFN (4mm x 3mm)
(Reference LTC DWG # 05-08-1695 Rev C)
0.70 0.05 PACKAGE OUTLINE 0.25 0.05 3.30 0.05 (2 SIDES) 0.50 BSC 4.00 0.10 (2 SIDES) R = 0.05 TYP 3.00 0.10 (2 SIDES) 1.70 0.05 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.35 x 45 CHAMFER 0.75 0.05 6 0.25 0.05 3.30 0.05 (2 SIDES) 1 0.50 BSC
(UE12/DE12) DFN 0905 REV C
3.60 0.05 1.70 0.05 2.20 0.05 (2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 0.40 0.10 12
7
PIN 1 TOP MARK (NOTE 6)
0.200 REF
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
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14
LT3012B
PACKAGE DESCRIPTIO U
FE Package 16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BB
4.90 - 5.10* (.193 - .201) 3.58 (.141) 16 1514 13 12 1110 6.60 0.10 4.50 0.10
SEE NOTE 4
3.58 (.141)
9
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
LT3012B RELATED PARTS
PART NUMBER LT1020 DESCRIPTION 125mA, Micropower Regulator and Comparator COMMENTS 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 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 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, ThinSOT 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
LT1120/LT1120A 125mA, Micropower Regulator and Comparator
LT1121/ LT1121HV LT1129 LT1676 LT1761 LT1762 LT1763
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
LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDO
LT1766 LT1776 LT1934/ LT1934-1 LT1956 LT1962
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
LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDO
LT1964 LT3010
200mA, Low Noise Micropower, Negative LDO 100mA, 3V to 80V, Low Noise Micropower LDO
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16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 0206 * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2006

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