ADP5056ACCZ-R7 datasheet(24/31 Pages) AD

24 / 31 page

ADP5056

Data Sheet

Rev. 0 | Page 24 of 31

POWER DISSIPATION

The total power dissipation in the ADP5056 simplifies to

PD = PBUCK1 + PBUCK2 + PBUCK3

where:

PD is the power dissipation in the package.

PBUCK1 is the power dissipation of Channel 1.

PBUCK2 is the power dissipation of Channel 2.

PBUCK3 is the power dissipation of Channel 3.

Buck Regulator Power Dissipation

The power dissipation (PLOSS) for each buck regulator includes

power switch conduction losses (PCOND), switching losses (PSW),

and transition losses (PTRAN). Other sources of power dissipation

exist, but these sources are generally less significant at the high

output currents of the application thermal limit.

Use the following equation to estimate the power dissipation of

the buck regulator:

PLOSS = PCOND + PSW + PTRAN

Power Switch Conduction Loss (PCOND)

Power switch conduction losses are caused by the flow of output

current through both the high-side and low-side power switches.

Each of these switches has internal on resistance (RDSON).

Use the following equation to estimate the power switch

conduction loss:

PCOND = (RDSON_HS × D + RDSON_LS × (1 − D)) × IOUT2

where:

RDSON_HS is the on resistance of the high-side MOSFET.

RDSON_LS is the on resistance of the low-side MOSFET.

Switching Loss (PSW)

Switching losses are associated with the current drawn by the

driver to turn the power devices on and off at the switching

frequency. Each time a power device gate is turned on or off,

the driver transfers a charge from the input supply to the gate,

and then from the gate to ground. Use the following equation to

estimate the switching loss:

PSW = (CGATE_HS + CGATE_LS) × VIN2 × fSW

where:

CGATE_HS is the gate capacitance of the high-side MOSFET.

CGATE_LS is the gate capacitance of the low-side MOSFET.

Transition Loss (PTRAN)

Transition losses occur because the high-side MOSFET cannot

turn on or off instantaneously. During a switch node transition,

the MOSFET provides all the inductor current. The source to

drain voltage of the MOSFET is half the input voltage, resulting

in power loss. Transition losses increase with both load and input

voltage and occur twice for each switching cycle. Use the following

equation to estimate the transition loss:

PTRAN = 0.5 × VIN × IOUT × (tR + tF) × fSW

where:

tR is the rise time of the switch node.

tF is the fall time of the switch node.

JUNCTION TEMPERATURE

The junction temperature of the die is the sum of the ambient

temperature of the environment and the temperature rise of the

package due to power dissipation, as shown in the following

equation:

TJ = TA + TR

where:

TJ is the junction temperature.

TA is the ambient temperature.

TR is the rise in temperature of the package due to power

dissipation.

The rise in temperature of the package is directly proportional

to the power dissipation in the package. The proportionality

constant for this relationship is the thermal resistance from the

junction of the die to the ambient temperature, as shown in the

following equation:

TR = θJA × PD

where:

θJA is the thermal resistance from the junction of the die to the

ambient temperature of the package (see Table 4).

An important factor to consider is that the thermal resistance

value is based on a 4-layer, 4 inch × 3 inch PCB with 2.5 oz. of

copper, as specified in the JEDEC standard, whereas real-world

applications may use PCBs with different dimensions and a

different number of layers.

It is important to maximize the amount of copper used to

remove heat from the device. Copper exposed to air dissipates

heat better than copper used in the inner layers. Connect Pin 35,

Pin 36, and Pin 37 to the ground plane with the maximum

number of vias.

ADP5056ACCZ-R7 数据表(PDF) 24 Page - Analog Devices

ADP5056ACCZ-R7 数据表(HTML) 24 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

数据表下载

链接网址

ADP5056ACCZ-R7 数据表(PDF) 24 Page - Analog Devices

ADP5056ACCZ-R7 数据表(HTML) 24 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

数据表 下载

链接网址

数据表下载