ADP1828YRQZ-R7 datasheet(17/32 Pages) AD

17 / 32 page

ADP1828

Rev. 0 | Page 17 of 32

COMPENSATION

The control loop is compensated by an external series RC

network from COMP to FB and sometimes requires a series

RC in parallel with the top voltage divider resistor. COMP is

the output of the internal error amplifier.

The internal error amplifier compares the voltage at FB to the

internal 0.6 V reference voltage. The difference between the FB

voltage and the 0.6 V reference voltage is amplified by the open-

loop voltage 1000 volt-to-volt gain of the error amplifier. To

optimize the ADP1828 for stability and transient response for

a given set of external components and input/output voltage

conditions, choose the compensation components carefully. For

more information on choosing the compensation components,

see the Compensating the Voltage Mode Buck Regulator

section.

POWER-GOOD INDICATOR

The ADP1828 features an open-drain power-good output

(PGOOD) that sinks current when the output voltage drops

8.3% below or rises 25% above the nominal regulation voltage.

Two comparators measure the voltage at FB to set these thresh-

olds. The PGOOD comparator directly monitors FB, and the

threshold is fixed at 0.55 V for undervoltage and 0.75 V for

overvoltage. The PGOOD output also sinks current if an

overtemperature or input undervoltage condition is detected

and is operational with power-input voltage as low as 1.0 V.

Use this output as a logical power-good signal by connecting a

pull-up resistor from PGOOD to an appropriate supply voltage.

THERMAL SHUTDOWN

In most applications, the ADP1828 controller itself does not

generate a significant amount of heat under normal conditions,

even when driving relatively large MOSFETs. However, the

surrounding power components or other circuits on the same

PCB could heat up the PCB to an unsafe operating temperature.

A thermal shutdown protection circuit on the ADP1828 shuts

off the LDO and the controllers if the die temperature exceeds

approximately 145°C, but this is a gross fault protection only

and should not be depended on for system reliability.

SHUTDOWN CONTROL

The ADP1828 dc-to-dc converter features a low power shut-

down mode that reduces the quiescent supply current to 20 μA,

or 40 μA when IN is tied to VREG. To shut down the ADP1828,

drive EN low. To turn it on, drive EN high or tristate EN. For

automatic startup, connect EN to IN.

TRACKING

The ADP1828 features a tracking input, TRK that makes the

output voltage track another voltage, that is, the master voltage.

This feature is especially useful in core and I/O voltage sequencing

applications where the output of the ADP1828 can be set to

track and not exceed another voltage.

The internal error amplifier includes three positive inputs—the

internal 0.6 V reference voltage, and the SS and TRK pins. The

error amplifier regulates the FB pin to the lowest of the three

inputs. To track a supply voltage, tie the TRK pin to a resistor

divider from the voltage to be tracked. If the TRK function is

not used, tie the TRK pin to VREG.

ADP1828YRQZ-R7 数据表(PDF) 17 Page - Analog Devices

ADP1828YRQZ-R7 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 29 30 31 32

数据表下载