ATtiny43U datasheet(36/182 Pages) ATMEL

36 / 182 page

8048B–AVR–03/09

ATtiny43U

Power Supply and On-Chip Boost Converter

In order to work properly microcontrollers typically require a supply voltage level that can not be

provided by battery packs of less than two or three battery cells. This constraint adds to size,

cost and complexity of the design. The integrated boost converter of ATtiny43U bridges the gap

between minimum supply voltage of the device and typical output voltages of single-cell stan-

dard, alkaline, Lithium, NiCd or NiMH batteries. The boost converter enables the device to be

powered from a source with a supply voltage well below 1V.

A block diagram illustrating the use of the boost converter is shown in Figure 8-1, below.

Figure 8-1.

Block Diagram of Boost Converter Usage.

8.1

Overview

A boost converter is a device that converts a DC voltage to a higher level. The integrated boost

converter of ATtiny43U provides the microcontroller (and its peripherals) with a fixed supply volt-

age, generated from an external supply of lower voltage.

The ATtiny43U boost converter is a switching type, step-up converter that uses an external

inductor, a diode and bypass capacitors. The boost converter is self-sufficient, completely inde-

pendent and does not need any control from the MCU. The converter starts automatically as

soon as there is sufficient voltage at the V

BAT pin. See Table 20-7 on page 159 for electrical

characteristics.

The microcontroller starts as soon as the regulated output of the boost converter rises above

power-on and brown-out reset levels (if enabled), as described in section “System Control and

Reset” on page 48. After the MCU is released from reset and has started running the application

software can then measure the battery voltage and decide if there is sufficient voltage to con-

tinue operation.

The boost converter continuously switches between storing energy in and draining energy from

the external inductor. During the charge phase the current through the inductor ramps up at a

rate determined by the converter input voltage. During the discharge phase energy stored in the

inductor is released to the load and the current in the inductor ramps down at a rate determined

by the difference between the input and output voltages.

The boost converter requires some external components to operate. See Figure 8-2 on page 37

for component placement. The circuit is completed by inserting an inductor between node VIN

and pin LSW, and a Schottky diode between pins LSW and V

CC. In addition, an input capacitor

and external bypass capacitor from V

CC to GND are typically required. See “Typical Applica-

tions” on page 46 for more details.

REGULATOR

MCU

EXTERNAL

COMPONENTS

VBAT

LSW

ATtiny43U

I/O

VCC

GND

VIN

ATtiny43U датащи(PDF) 36 Page - ATMEL Corporation

ATtiny43U датащи(HTML) 36 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL