LT3024EDE

LT3024 Dual 100mA/500mA Low Dropout, Low Noise, Micropower Regulator FEATURES n n n n n n n n n n n n n n DESCRIPTION The LT®3024 is a dual, micropower, low noise, low dropout regulator. With an external 0.01μF bypass capacitor, output noise drops to 20μVRMS over a 10Hz to 100kHz bandwidth. Designed for use in battery-powered systems, the low 30μA quiescent current per output makes it an ideal choice. In shutdown, quiescent current drops to less than 0.1μA. Shutdown control is independent for each output, allowing for flexibility in power management. The device is capable of operating over an input voltage range of 1.8V to 20V. The device can supply 100mA of output current from Output 2 with a dropout voltage of 300mV. Output 1 can supply 500mA of output current with a dropout voltage of 300mV. Quiescent current is well controlled in dropout. The LT3024 regulator is stable with output capacitors as low as 1μF for the 100mA output and 3.3μF for the 500mA output. Small ceramic capacitors can be used without the series resistance required by other regulators. Internal protection circuitry includes reverse-battery protection, current limiting, thermal limiting and reverse current protection. The device is available as an adjustable device with a 1.22V reference voltage. The LT3024 regulator is available in the thermally enhanced 16-lead TSSOP and 12-lead, low profile (4mm × 3mm × 0.75mm) DFN packages. Low Noise: 20μVRMS (10Hz to 100kHz) Low Quiescent Current: 30μA/Output Wide Input Voltage Range: 1.8V to 20V Output Current: 100mA/500mA Very Low Shutdown Current: 3300pF CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP ≥ 1000pF Figure 2. Output 2 Stability Figure 3. Output 1 Stability 3024fa 14 LT3024 APPLICATIONS INFORMATION 20 0 CHANGE IN VALUE (%) CHANGE IN VALUE (%) X5R –20 –40 –60 Y5V –80 –100 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF 40 20 0 –20 –40 –60 –80 Y5V X5R 0 2 4 8 6 10 12 DC BIAS VOLTAGE (V) 14 16 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10μF –100 50 25 75 –50 –25 0 TEMPERATURE (°C) 100 125 3024 F04 3024 F05 Figure 4. Ceramic Capacitor DC Bias Characteristics Figure 5. Ceramic Capacitor Temperature Characteristics 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. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure 6’s trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise. COUT = 10μF CBYP = 0.01μF ILOAD = 100mA Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125°C). The power dissipated by the device will be made up of two components for each output: 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 ground pin current can be found by examining the GND Pin Current curves in the Typical Performance Characteristics section. Power dissipation will be equal to the sum of the two components listed above. The LT3024 regulator has internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions, the maximum junction temperature rating of 125°C 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. VOUT 500μV/DIV 100ms/DIV 3024 F06 Figure 6. Noise Resulting from Tapping on a Ceramic Capacitor For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board 3024fa 15 LT3024 APPLICATIONS INFORMATION 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. FE Package, 16-Lead TSSOP COPPER AREA TOPSIDE* 2500mm2 1000mm2 225mm2 100mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500mm2 2500mm2 2500mm2 2500mm2 38°C/W 43°C/W 48°C/W 60°C/W The power dissipated by each output will be equal to: IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX)) Where for Output 1: IOUT(MAX) = 500mA VIN(MAX) = 5V IGND at (IOUT = 500mA, VIN = 5V) = 9mA For Output 2: IOUT(MAX) = 100mA VIN(MAX) = 5V IGND at (IOUT = 100mA, VIN = 5V) = 2mA So for Output 1: P = 500mA (5V – 3.3V) + 9mA (5V) = 0.90W For Output 2: P = 100mA (5V – 2.5V) + 2mA (5V) = 0.26W The thermal resistance will be in the range of 35°C/W to 55°C/W depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: (0.90W + 0.26W) 50°C/W = 57.8°C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50°C + 57.8°C = 107.8°C Protection Features The LT3024 regulator 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, reverse output voltages and reverse voltages from output to input. The two regulators have common *Device is mounted on topside. Table 2. UE Package, 12-Lead DFN COPPER AREA TOPSIDE* 2500mm2 1000mm2 225mm2 100mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500mm2 2500mm2 2500mm2 2500mm2 40°C/W 45°C/W 50°C/W 62°C/W *Device is mounted on topside. The thermal resistance junction-to-case (θJC), measured at the Exposed Pad on the back of the die is 10°C/W for the DFN package and 8°C/W for the TSSOP package. Calculating Junction Temperature Example: Given Output 1 set for an output voltage of 3.3V, Output 2 set for an output voltage of 2.5V, an input voltage range of 3.8V to 5V, an output current range of 0mA to 500mA for Output 1, an output current range of 0mA to 100mA for Output 2 and a maximum ambient temperature of 50°C, what will the maximum junction temperature be? 3024fa 16 LT3024 APPLICATIONS INFORMATION VIN and GND pins and are thermally coupled, however, the two outputs of the LT3024 operate independently. They can be shut down independently and a fault condition on one output will not affect the other output electrically. 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 125°C. The input of the device will withstand reverse voltages of 20V. Current flow into the device will be limited to less than 1mA (typically less than 100μA) and 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 output of the LT3024 can be pulled below ground without damaging the device. If the input is left open circuit or grounded, the output can be pulled below ground by 20V. The output will act like an open circuit; no current will flow out of the pin. If the input is powered by a voltage source, the output will source the short-circuit current of the device and will protect itself by thermal limiting. In this case, grounding the SHDN1/SHDN2 pins will turn off the device and stop the output from sourcing the shortcircuit current. The ADJ pins 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 pins 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. In situations where the ADJ pins are connected to a resistor divider that would pull the pins above their 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 1.22V reference when the output is forced to 20V. 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 13V difference between output and ADJ pin divided by the 5mA maximum current into the ADJ pin yields a minimum top resistor value of 2.6k. 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 7. When the IN pin of the LT3024 is forced below either OUT pin or either OUT pin is pulled above the IN pin, input current for the corresponding regulator will typically drop to less than 2μA. This can happen if the input of the device 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 SHDN1/SHDN2 pin will have no effect on the reverse output current when the output is pulled above the input. 100 REVERSE OUTPUT CURRENT (μA) TA = 25°C 90 VIN = 0V = VADJ V 80 OUT CURRENT FLOWS 70 INTO OUTPUT PIN 60 50 40 30 20 10 0 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10 3024 F07 Figure 7. Reverse Output Current 3024fa 17 LT3024 PACKAGE DESCRIPTION DE/UE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695 Rev D) 0.70 ± 0.05 3.30 ± 0.05 1.70 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.50 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ± 0.10 (2 SIDES) 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 × 45° CHAMFER 1 0.50 BSC 2.50 REF 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD (UE12/DE12) DFN 0806 REV D 3.60 ± 0.05 2.20 ± 0.05 7 R = 0.115 TYP 0.40 ± 0.10 12 PIN 1 TOP MARK (NOTE 6) 0.200 REF 0.75 ± 0.05 6 0.25 ± 0.05 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 3024fa 18 LT3024 PACKAGE DESCRIPTION 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 6.60 ± 0.10 4.50 ± 0.10 SEE NOTE 4 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 3024fa 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. 19 LT3024 RELATED PARTS PART NUMBER LT1129 LT1175 LT1185 LT1761 LT1762 LT1763 LT1764/LT1764A LTC1844 LT1962 LT1963/LT1963A LT1964 LT3023 LTC3407 DESCRIPTION 700mA, Micropower, LDO 500mA, Micropower Negative LDO 3A, Negative LDO 100mA, Low Noise Micropower, LDO 150mA, Low Noise Micropower, LDO 500mA, Low Noise Micropower, LDO 3A, Low Noise, Fast Transient Response, LDO 150mA, Very Low Drop-Out LDO 300mA, Low Noise Micropower, LDO COMMENTS VIN: 4.2V to 30V, VOUT(MIN) = 3.75V, IQ = 50μA, ISD = 16μA, DD, SOT-223, S8,TO220, TSSOP20 Packages Guaranteed Voltage Tolerance and Line/Load Regulation, VIN: –20V to –4.3V, VOUT(MIN) = –3.8V, IQ = 45μA, ISD = 10μA, DD,SOT-223, S8 Packages Accurate Programmable Current Limit, Remote Sense, VIN: –35V to –4.2V, VOUT(MIN) = –2.40V, IQ = 2.5mA, ISD