ISL8272MEVAL2Z datasheet(21/59 Pages) RENESAS

21 / 59 page

ISL8272M

FN8670 Rev.5.00

Page 21 of 59

Nov 8, 2017

Thermal Overload Protection

The ISL8272M includes a thermal sensor that continuously

measures the internal temperature of the module and shuts

down the controller when the temperature exceeds the preset

limit. The default temperature limit is set to +125°C in the

factory, but can be changed with PMBus command

OT_FAULT_LIMIT.

The default response from an over-temperature fault is an

immediate shutdown without retry. Retry settings can be

programmed with the PMBus command OT_FAULT_RESPONSE.

Hysteresis is implemented with the over-temperature fault retry.

If retry is enabled, the module will shut down immediately upon

an over-temperature fault event and then check the temperature

every 70ms. If the temperature falls below the over-temperature

warning level, the module will restart. The over-temperature

warning is +105°by default and programmable with the PMBus

command OT_WARN_LIMIT. Note that fault retry is not supported

in the current sharing configuration.

Digital-DC Bus

The Digital-DC Communications (DDC) bus is used to

communicate between Intersil digital power modules and digital

controllers. This dedicated bus provides the communication

channel between devices for features such as current sharing,

sequencing, and fault spreading. The DDC pin on all Digital-DC

devices in an application should be connected together. A pull-up

resistor is required on the DDC bus in order to guarantee the rise

time as shown in Equation 2:

where RPU is the DDC bus pull-up resistance and CLOAD is the

bus loading. The pull-up resistor may be tied to an external 3.3V

or 5V supply as long as this voltage is present prior to or during

device power-up. In principle, each device connected to the DDC

bus presents approximately 10pF of capacitive loading and each

inch of FR4 PCB trace introduces approximately 2pF. The ideal

design uses a central pull-up resistor that is well-matched to the

total load capacitance.

Active Current Sharing

Paralleling multiple ISL8272M modules can increase the output

current capability of a single power rail. By connecting the DDC

and SYNC pins of each module together and configuring the

modules as a current sharing rail, the units will share the current

equally within a few percent.

Figure 27 illustrates a typical connection for two modules.

The ISL8272M uses a DDC bus based digital current sharing

technique to balance the steady state module output current by

aligning the load lines of member modules to a reference

module.

When multiple ISL8272M modules are connected for current

sharing, a non-zero active droop resistance must be set to add

artificial resistance in the output voltage path to control the slope

of the load line curve, calibrating out the physical parasitic

mismatches due to power train components and PCB layout. The

active droop resistance can be programmed with the PMBus

command VOUT_DROOP based on Equation 3. Typically, higher

droop value offers a more accurate dynamic current sharing at

the sacrifice of output load regulation. 1% droop at full load will

be a good trade-off between output load regulation and dynamic

current sharing.

Upon system start-up, the module with the lowest device position

as selected in DDC_CONFIG is defined as the reference module.

The remaining modules are members. The reference module

broadcasts its current over the DDC bus. The members use the

reference current information to trim their voltages (VMEMBER) to

balance the current loading of each module in the system.

Rise Time

RPUCLOAD 1s



(EQ. 2)

ISL8272M

VOUT

ISL8272M

VIN

COUT

CIN

COUT

CIN

DDC

3.3V TO 5V

SYNC

FIGURE 27. CURRENT SHARING GROUP

VOUT

ILOAD MAX



---------------------------------- 0.005



Droop

VOUT

ILOAD MAX



---------------------------------- 0.01





(EQ. 3)

-R

VREFERENCE

VMEMBER

IMEMBER

IREFERENCE

IOUT

FIGURE 28. ACTIVE CURRENT SHARING

ISL8272MEVAL2Z датащи(PDF) 21 Page - Renesas Technology Corp

ISL8272MEVAL2Z датащи(HTML) 21 Page - Renesas Technology Corp

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

датащи скачать

ссылки URL