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ADP1073AR-12 датащи(PDF) 5 Page - Analog Devices |
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ADP1073AR-12 датащи(HTML) 5 Page - Analog Devices |
5 / 16 page ADP1073 –5– REV. 0 TEMPERATURE – C 2300 2100 1100 40 085 25 70 1900 1700 1500 1300 VIN = 1.5V RL = 100k Figure 11. “Gain Block” Gain vs. Temperature THEORY OF OPERATION The ADP1073 is a flexible, low power switch mode power supply (SMPS) controller. The regulated output voltage can be greater than the input voltage (boost or step-up mode) or less than the input (buck or step-down mode). This device uses a gated-oscillator technique to provide very high performance with low quiescent current. A functional block diagram of the ADP1073 is shown on the front page. The internal 212 mV reference is connected to one input of the comparator, while the other input is externally connected (via the FB pin) to a feedback network connected to the regulated output. When the voltage at the FB pin falls below 212 mV, the 19 kHz oscillator turns on. A driver amplifier pro- vides base drive to the internal power switch and the switching action raises the output voltage. When the voltage at the FB pin exceeds 212 mV, the oscillator is shut off. While the oscillator is off, the ADP1073 quiescent current is only 100 µA. The com- parator includes a small amount of hysteresis, which ensures loop stability without requiring external components for fre- quency compensation. The maximum current in the internal power switch can be set by connecting a resistor between VIN and the ILIM pin. When the maximum current is exceeded, the switch is turned OFF. The current limit circuitry has a time delay of about 2 µs. If an external resistor is not used, connect ILIM to VIN. Further infor- mation on ILIM is included in the Limiting the Switch Current section of this data sheet. The ADP1073 internal oscillator provides 38 µs ON and 15 µs OFF times, which is ideal for applications where the ratio be- tween VIN and VOUT is roughly a factor of three (such as gener- ating +5 V from a single 1.5 V cell). Wider range conversions, as well as step-down converters, can also be accomplished with a slight loss in the maximum output power that can be obtained. An uncommitted gain block on the ADP1073 can be connected as a low-battery detector, linear post-regulator or undervoltage lockout detector. The inverting input of the gain block is inter- nally connected to the 212 mV reference. The noninverting input is available at the SET pin. A resistor divider, connected between VIN and GND with the junction connected to the SET pin, causes the AO output to go LOW when the input voltage goes below the low battery set point. The AO output is an open collector NPN transistor that can sink 100 µA. The ADP1073 provides external connections for both the col- lector and emitter of its internal power switch, which permits both step-up and step-down modes of operation. For the step- up mode, the emitter (Pin SW2) is connected to GND and the collector (Pin SW1) drives the inductor. For step-down mode, the emitter drives the inductor while the collector is connected to VIN. The output voltage of the ADP1073 is set with two external resistors. Three fixed-voltage models are also available: ADP1073-3.3 (+3.3 V), ADP1073-5 (+5 V) and ADP1073-12 (+12 V). The fixed-voltage models are identical to the ADP1073, except that laser-trimmed voltage-setting resistors are included on the chip. Only three external components are required to form a +3.3 V, +5 V or +12 V converter. On the fixed-voltage models of the ADP1073, simply connect the feedback pin (Pin 8) directly to the output voltage. The ADP1073 oscillator only turns on when the output voltage is below the programmed voltage. When the output voltage is above the programmed voltage, the ADP1073 remains in its quiescent state to conserve power. Output ripple, which is in- herent in gated oscillator converters, is typically 125 mV for a 5 V output and 300 mV for a 12 V output. This ripple voltage can be greatly reduced by inserting the gain-block between the output and the FB pin. Further information and a typical circuit are shown in the Programming the Gain Block section. |
Аналогичный номер детали - ADP1073AR-12 |
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Аналогичное описание - ADP1073AR-12 |
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