MAX8569B Просмотр технического описания (PDF) - Maxim Integrated

Номер в каталоге

Компоненты Описание

производитель

MAX8569B

200mA Step-Up Converters in 6-Pin SOT23 and TDFN

Maxim Integrated 

200mA Step-Up Converters in 6-Pin

SOT23 and TDFN

Detailed Description

The MAX8569A and MAX8569B compact high-efficien-

cy step-up converters feature low-quiescent supply cur-

rent to ensure the highest possible efficiency over a

wide load range. With a minimum 1.5V input voltage,

these devices are well suited for applications with two

alkaline cells, two nickel-metal-hydride (NiMH) cells, or

one lithium-ion (Li+) cell. When SHDN is low, the output

is connected to the battery through the inductor and an

internal p-channel MOSFET. This allows the input bat-

tery to be used as a backup or real-time clock supply

when the converter is off by eliminating the voltage drop

across the MOSFET body diode. These devices are

ideal for low-power applications where a small footprint

is critical. The internal synchronous rectifier improves

efficiency significantly and reduces size and cost by

eliminating the need for an external Schottky diode.

Control Scheme

The MAX8569A/MAX8569B feature a current-limited

control scheme that provides ultra-low quiescent current

and high efficiency over a wide output current range.

The switching cycles are not controlled by an oscillator.

Instead, switch on-time is terminated when the inductor

current reaches the 780mA (typ) n-channel current limit,

or when the 5µs maximum n-channel switch on-time is

reached. Following each on-cycle, the synchronous rec-

tifier turns on, shunts the MOSFET body diode, and the

inductor current ramps to zero before another cycle

begins. The next cycle occurs when the error compara-

tor senses that the output has fallen below the regulation

threshold.

Applications Information

Shutdown

Drive SHDN low to shut down the MAX8569A/

MAX8569B and reduce the input current to less than

1µA. During shutdown, the battery input is connected

to the output through the inductor and the internal syn-

chronous rectifier. This allows the input battery (rather

than a separate backup battery) to provide backup

power for devices such as an idled microcontroller,

SRAM, or real-time clock, without the usual diode for-

ward drop. Drive SHDN to VOUT (logic-high) to enable

the IC for normal operation.

1.5V TO 3V

INPUT C1

10µF

R1

220kΩ

R2

1MΩ

L1

10µH

C2

0.01µF

2

BATT

5

OUT

4

LX

MAX8569A

6

FB

1

SHDN

GND

3

R3

168kΩ

R4

100kΩ

3.3V OUTPUT

C3

22µF

Figure 1. Typical Application Circuit for MAX8569A

1.5V TO 3V

INPUT C1

10µF

L1

10µH

2

BATT

5

OUT

4

LX

MAX8569B

6

RST

ON

OFF

1

SHDN

GND

3

3.3V

C3

OUTPUT

22µF R1

100kΩ

RESET

OUTPUT

Figure 2. Typical Application Circuit for MAX8569B

_______________________________________________________________________________________ 7

Share Link: