ADP3331

a Adjustable Output Ultralow IQ, 200 mA, SOT-23, anyCAP™ Low Dropout Regulator ADP3331 FUNCTIONAL BLOCK DIAGRAM Q1 THERMAL PROTECTION ERR Q2 SD DRIVER gm IN OUT FEATURES High Accuracy Over Line and Load: 0.7% @ +25 C, 1.4% Over Temperature Ultralow Dropout Voltage: 140 mV (Typ) @ 200 mA Can Be Used as a High Current (>1 A) LDO Controller Requires Only CO = 0.47 F for Stability anyCAP = Stable with Any Type of Capacitor (Including MLCC) Current and Thermal Limiting Low Noise Low Shutdown Current: 230°C/W for a standard SOT-23 lead frame. Figure 22 shows the difference between the standard SOT-23 and the Chip-onLead lead frames. SILICON DIE SILICON DIE WITH ELECTRICALLY ISOLATED DIE ATTACH NORMAL SOT-23-6 PACKAGE THERMALLY ENHANCED CHIP-ON-LEAD PACKAGE Figure 22. Chip-on-Lead Package Calculating Junction Temperature The output voltage can be adjusted to any voltage from 1.5 V to 10 V. For example, the Feedback Resistor Selection Table shows some representative feedback resistor values for output voltages in the specified range. Table I. Feedback Resistor Selection Device power dissipation is calculated as follows: PD = ( VIN – VOUT) ILOAD + (VIN ) IGND Where ILOAD and IGND are load current and ground current, VIN and VOUT are the input and output voltages respectively. Assuming the worst case operating conditions are ILOAD = 200 mA, IGND = 4 mA, V IN = 4.2 V and VOUT = 3.0 V, the device power dissipation is: PD = (4.2 V – 3.0 V) 200 mA + (4.2 V) 4 mA = 257 mW The proprietary package used on the ADP3331 has a thermal resistance of 165°C/W when placed on a 4-layer board, and 190°C/W when placed on a 2-layer board. This allows the ambient temperature to be significantly higher for a given power dissipation than with a standard package. Assuming a 4-layer board, the junction temperature rise above ambient will be approximately equal to: ∆TJA = 0.257 W × 165°C/W = 42.4° C –7– VOUT 1.5 V 1.8 V 2.2 V 2.7 V 3.3 V 5V 9V R1 (1% Resistor) 243 kΩ 340 kΩ 422 kΩ 511 kΩ 634 kΩ 953 kΩ 1.00 MΩ R2 (1% Resistor) 1.00 MΩ 698 kΩ 511 kΩ 412 kΩ 365 kΩ 301 kΩ 154 kΩ Output voltages above 5 V and below 1.6 V will require nonstandard resistor values or adding an additional resistor to the REV. 0 ADP3331 To limit the junction temperature to 125°C, the maximum allowable ambient temperature is: TA(MAX) = +125°C – 42.4°C = +82.6°C Shutdown Mode conjunction with the preload and noise reduction capacitor. Further increases in the output capacitance may be acceptable if the output already has a sizable load during start-up. Higher Output Current Error Flag Dropout Detector VIN = 3.3V C1 47 F MJE253* R1 50 VOUT = 1.8V @ 1A The ADP3331 will maintain its output voltage over a wide range of load, input voltage, and temperature conditions. If the output is about to lose regulation, due to the input voltage approaching the dropout level, the error flag will be activated. The ERR output is an open collector, which will be driven low. Once set, the ERR flag’s hysteresis will keep the output low until a small margin of operating range is restored either by raising the supply voltage or reducing the load. Low Voltage Applications IN OUT C2 10 F FB 340k ADP3331 SD GND *REQUIRES HEAT SINK ERR 698k In applications where the output voltage is 2.2 V or less, the ADP3331 may begin to exhibit some turn-on overshoot. The degree of overshoot is determined by several factors: the output voltage setting, the output load, the noise reduction capacitor, and the output capacitor. The output voltage setting is determined by the application and cannot be tailored for minimum overshoot. In general, for output voltages 2.2 V or less, the overshoot becomes larger as the output voltage decreases. The output load is also determined by the system requirements. However, if the ADP3331 has no load on the output during start-up, a small amount of preload can be added to minimize overshoot. A preload of 2 µA to 20 µA is recommended. A noise reduction capacitor, if not already being used, is suggested to reduce the overshoot. Values in the range of 10 pF to 100 pF works best along with the preload suggested previously. The output capacitor can be adjusted to minimize the overshoot. Values in the 0.47 µF to 1.0 µF range should be used in Figure 23. High Output Current Linear Regulator Printed Circuit Board Layout Considerations Use the following general guidelines when designing printed circuit boards: 1. PC board traces with larger cross sectional areas will remove more heat from the ADP3331. For optimum heat transfer, specify thick copper and use wide traces. 2. The thermal resistance can be decreased by approximately 10% by adding a few square centimeters of copper area to the lands connected to the pins of the LDO. 3. The feedback pin is a high impedance input, and care should be taken when making a connection to this pin. The voltage setting resistors and noise reduction network must be located as close as possible. Long PC board traces are not recommended. Avoid routing traces near possible noise sources. OUTLINE DIMENSIONS Dimensions shown in inches and (mm). PRINTED IN U.S.A. 0.022 (0.55) 0.014 (0.35) 6-Lead Surface Mount RT-6 (SOT-23-6) 0.122 (3.10) 0.106 (2.70) 0.071 (1.80) 0.059 (1.50) PIN 1 6 1 5 2 4 3 0.118 (3.00) 0.098 (2.50) 0.037 (0.95) BSC 0.075 (1.90) BSC 0.051 (1.30) 0.035 (0.90) 0.059 (0.15) 0.000 (0.00) 0.057 (1.45) 0.035 (0.90) 0.020 (0.50) SEATING 0.010 (0.25) PLANE 10° 0.009 (0.23) 0° 0.003 (0.08) –8– REV. 0 C3624–2.5–6/99 Applying a TTL level high signal to the shutdown (SD) pin, or tying it to the input pin, will turn the output ON. Pulling the SD to 0.4 V or below, or tying it to ground, will turn the output OFF. In shutdown mode, the quiescent current is reduced to less than 1 µA. The ADP3331 can source up to 200 mA without any heat sink or pass transistor. If higher current is needed, an appropriate pass transistor can be used, as in Figure 23, to increase the output current to 1 A.