ISL68147IRAZ datasheet(16/47 Pages) RENESAS

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ISL68147

FN8880 Rev.2.00

Page 16 of 47

Jul 14, 2017

Voltage Regulation

Output voltage is sensed through the remote sense differential

amplifier and digitized. From this point, the regulation loop is

entirely digital. Traditional PID controls are used in conjunction

with several enhanced methods to compensate the voltage

regulation loop and tune the transient response.

Current Feedback

Current feedback in a voltage regulator is often used to ease the

stability design of the voltage feedback path. Additionally, many

microprocessors require the voltage regulator to have a

controlled output resistance (known as load line or droop

regulation) and this is accomplished using current feedback.

For applications requiring droop regulation, the designer simply

specifies the output resistance desired using PowerNavigator.

Current feedback stability benefits are available for rails that do

not specify droop regulation such as system agent. For these

applications, the designer can enable AC current feedback in

PowerNavigator. With this configuration, the DC output voltage

will be steady regardless of load current.

Power-On Reset (POR)

Initialization of the ISL68147 begins after VCC crosses its rising

POR threshold. When POR conditions are met, the internal 1.2V

LDO is enabled and basic digital subsystem integrity checks

begin. During this process, the controller will load the selected

user configuration from NVM as indicated by the CONFIG pin

resistor value, read VIN UVLO thresholds from memory, and start

the telemetry subsystem. With telemetry enabled, VIN can be

monitored to determine when it exceeds its user-programmable,

rising UVLO threshold. After VCC and VIN satisfy their respective

voltage conditions, the controller is in its shutdown state. It will

transition to its active state and begin soft-start when the state of

EN0/EN1 command is at start-up. While in shutdown mode, the

PWM outputs are held in a high-impedance state to ensure the

drivers remain off.

Soft-Start Delay and Ramp Times

It might be necessary to set a delay from when an enable signal

is received until the output voltage starts to ramp to its target

value. In addition, the designer might want to precisely set the

time required for an output to ramp to its target value after the

delay period has expired. These features can be used as part of

an overall inrush current management strategy or to precisely

control how fast a load IC is turned on. The ISL68147 gives the

system designer several options for precisely and independently

controlling both the delay and ramp time periods. The soft-start

delay period begins when the EN pin is asserted and ends when

the delay time expires.

The soft-start delay and ramp-up/down times can be configured

through PowerNavigator. The device needs approximately 200µs

after enable to initialize before starting to ramp up. When the

soft-start ramp period is set to 0ms, the output ramps up as

quickly as the output load capacitance and loop settings allow. It

is recommended to set the ramps to a non-zero value to prevent

inadvertent fault conditions due to excessive inrush current.

Stored Configuration Selection

As many as eight configurations can be stored and used at any

time using the on-board nonvolatile memory. Configurations are

assigned an identifier number between 0 and 7 at power-up. The

device will load the configuration indicated by the 1% resistor

value detected on the CONFIG pin. Resistor values are used to

indicate use of one of the eight possible configurations. Table 3

provides the resistor value corresponding to each configuration

identifier.

Only the most recent configuration with a given number can be

loaded. The device supports a total of eight stored operations. As

an example, a configuration with the identifier 0 could be saved

eight times or configurations with all eight identifiers could be

stored one time each for a total of eight save operations.

PowerNavigator provides a simple interface to save and load

configurations.

Fault Monitoring and Protection

The ISL68147 actively monitors temperature, input voltage,

output voltage, and output current to detect and report fault

conditions. Fault monitors trigger configurable protective

measures to prevent damage to a load. The power-good

indicators, PG0/PG1, are provided for linking to external system

monitors.

A high level of flexibility is provided in the ISL68147 fault logic.

Faults can be enabled or disabled individually. Each fault type

can also be configured to either latch off or retry indefinitely.

FIGURE 17. INPUT VOLTAGE SENSE CONFIGURATION

ADC

VINSEN

40.2k

VIN

10k

10nF

TABLE 3. RESISTOR VALUES TO CONFIGURATION MAPPING

R CONFIG

(Ω)

CONFIG

6800

1800

2200

2700

3300

3900

4700

5600

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