ADP2301AUJZ-R2 datasheet(17/28 Pages) AD

17 / 28 page

Data Sheet

ADP2300/ADP2301

Rev. C | Page 17 of 28

3.5

3.7

3.9

4.1

4.3

4.5

4.7

4.9

5.1

5.3

5.5

100

LOAD CURRENT (mA)

FOR STARTUP

FOR RUNNING

VOUT = 3.3V

fSW = 1.4MHz

Figure 43. Minimum Input Voltage vs. Load Current

Based on three conversion limitations (the minimum on time,

the minimum off time, and the bootstrap dropout voltage),

Figure 44 shows the voltage conversion limitations.

VOUT (V)

MAXIMUM INPUT FOR ADP2300

MAXIMUM INPUT FOR ADP2301

MINIMUM INPUT FOR ADP2300/ADP2301

Figure 44. Voltage Conversion Limitations

LOW INPUT VOLTAGE CONSIDERATIONS

For low input voltage between 3 V and 5 V, the internal boot

regulator cannot provide enough 5.0 V bootstrap voltage due to

the internal dropout voltage. As a result, the increased MOSFET

RDS(ON) reduces the available load current. To prevent this, add

an external small-signal Schottky diode from a 5.0 V external

bootstrap bias voltage. Because the absolute maximum rating

between the BST and SW pins is 6.0 V, the bias voltage should

be less than 5.5 V. Figure 45 shows the application diagram for

the external bootstrap circuit.

3V ~ 5V

VIN

BST

OFF

GND

ADP2300/

ADP2301

SCHOTTKY DIODE

5V BIAS

VOLTAGE

Figure 45. External Bootstrap Circuit for Low Input Voltage Application

PROGRAMMING THE PRECISION ENABLE

Generally, the EN pin can be easily tied to the VIN pin so that the

device automatically starts up when the input power is applied.

However, the precision enable feature allows the ADP2300/

ADP2301 to be used as a programmable UVLO by connecting

a resistive voltage divider to VIN, as shown in Figure 46. This

configuration prevents the start-up problems that can occur

when VIN ramps up slowly in soft start with a relatively high

load current.

ADP2300/

ADP2301

VIN

REN1

REN2

Figure 46. Precision Enable Used as a Programmable UVLO

The precision enable feature also allows the ADP2300/ADP2301 to

be sequenced precisely by using a resistive voltage divider with

another dc-to-dc output supply, as shown in Figure 47.

ADP2300/

ADP2301

REN1

REN2

OTHER DC-TO-DC

OUTPUT

Figure 47. Precision Enable Used as a Sequencing Control

from Another DC-to-DC Output

With a 1.2 µA pull-down current on the EN pin, the equation for

the start-up voltage in Figure 46 and Figure 47 is

μA













STARTUP

where:

VSTARTUP is the start-up voltage to enable the chip.

REN1 is the resistor from the dc source to EN.

REN2 is the resistor from EN to GND.

ADP2301AUJZ-R2 数据表(PDF) 17 Page - Analog Devices

ADP2301AUJZ-R2 数据表(HTML) 17 Page - Analog Devices

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

数据表下载

链接网址

ADP2301AUJZ-R2 数据表(PDF) 17 Page - Analog Devices

ADP2301AUJZ-R2 数据表(HTML) 17 Page - Analog Devices

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

数据表 下载

链接网址

数据表下载