Electronic Components Datasheet Search |
|
ADP3300ART-2.7 Datasheet(PDF) 6 Page - Analog Devices |
|
ADP3300ART-2.7 Datasheet(HTML) 6 Page - Analog Devices |
6 / 8 page REV. B ADP3300 –6– THEORY OF OPERATION The new anyCAP LDO ADP3300 uses a single control loop for regulation and reference functions. The output voltage is sensed by a resistive voltage divider consisting of R1 and R2 which is varied to provide the available output voltage option. Feedback is taken from this network by way of a series diode (D1) and a second resistor divider (R3 and R4) to the input of an amplifier. gm PTAT VOS R4 R3 D1 R1 ATTENUATION (VBANDGAP/V OUT) R2 (a) COMPENSATION CAPACITOR NONINVERTING WIDEBAND DRIVER Q1 INPUT CLOAD OUTPUT ADP3300 RLOAD PTAT CURRENT Figure 2. Functional Block Diagram A very high gain error amplifier is used to control this loop. The amplifier is constructed in such a way that at equilibrium it produces a large, temperature proportional input “offset voltage” that is repeatable and very well controlled. The temperature- proportional offset voltage is combined with the complimentary diode voltage to form a “virtual bandgap” voltage, implicit in the network, although it never appears explicitly in the circuit. Ultimately, this patented design makes it possible to control the loop with only one amplifier. This technique also improves the noise characteristics of the amplifier by providing more flexibility on the trade-off of noise sources that leads to a low noise design. The R1, R2 divider is chosen in the same ratio as the bandgap voltage to the output voltage. Although the R1, R2 resistor divider is loaded by the diode D1 and a second divider consisting of R3 and R4, the values are chosen to produce a temperature stable output. This unique arrangement specifically corrects for the loading of the divider so that the error resulting from base current loading in conventional circuits is avoided. The patented amplifier controls a new and unique noninverting driver that drives the pass transistor, Q1. The use of this special noninverting driver enables the frequency compensation to include the load capacitor in a pole splitting arrangement to achieve reduced sensitivity to the value, type and ESR of the load capacitance. Most LDOs place strict requirements on the range of ESR values for the output capacitor because they are difficult to stabilize due to the uncertainty of load capacitance and resis- tance. Moreover, the ESR value, required to keep conventional LDOs stable, changes depending on load and temperature. These ESR limitations make designing with LDOs more diffi- cult because of their unclear specifications and extreme variations over temperature. This is no longer true with the ADP3300 anyCAP LDO. It can be used with virtually any capacitor, with no constraint on the minimum ESR. The innovative design allows the circuit to be stable with just a small 0.47 µF capacitor on the output. Addi- tional advantages of the pole splitting scheme include superior line noise rejection and very high regulator gain, which leads to excel- lent line and load regulation. An impressive ±1.4% accuracy is guaranteed over line, load and temperature. Additional features of the circuit include current limit, thermal shutdown and noise reduction. Compared to the standard solu- tions that give warning after the output has lost regulation, the ADP3300 provides improved system performance by enabling the ERR pin to give warning before the device loses regulation. As the chip’s temperature rises above 165 °C, the circuit activates a soft thermal shutdown, indicated by a signal low on the ERR pin, to reduce the current to a safe level. To reduce the noise gain of the loop, the node of the main divider network (a) is made available at the noise reduction (NR) pin, which can be bypassed with a small capacitor (10 nF–100 nF). APPLICATION INFORMATION Capacitor Selection: anyCAP Output Capacitors: as with any micropower device, output transient response is a function of the output capacitance. The ADP3300 is stable with a wide range of capacitor values, types and ESR (anyCAP). A capacitor as low as 0.47 µF is all that is needed for stability. However, larger capacitors can be used if high output current surges are anticipated. The ADP3300 is stable with extremely low ESR capacitors (ESR ≈ 0), such as multilayer ceramic capacitors (MLCC) or OSCON. Input Bypass Capacitor: an input bypass capacitor is not required; however, for applications where the input source is high impedance or far from the input pins, a bypass capacitor is recom- mended. Connecting a 0.47 µF capacitor from the input to ground reduces the circuit’s sensitivity to PC board layout. If a bigger output capacitor is used, the input capacitor should be 1 µF minimum. Noise Reduction A noise reduction capacitor (CNR) can be used to further reduce the noise by 6 dB–10 dB (Figure 3). Low leakage capacitors in the 10 nF–100 nF range provide the best performance. For load current less than 200 µA, a 4.7 µF output capacitor provides the lowest noise and the best overall performance. Since the noise reduction pin (NR) is internally connected to a high impedance node, any connection to this node should be carefully done to avoid noise pickup from external sources. The pad connected to this pin should be as small as possible. Long PC board traces are not recommended. IN OUT ERR GND ADP3300-5 NR ON OFF SD C2 4.7 F 330k EOUT C1 1.0 F VOUT = 5V VIN CNR 10nF + + Figure 3. Noise Reduction Circuit |
Similar Part No. - ADP3300ART-2.7 |
|
Similar Description - ADP3300ART-2.7 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |