ISL68127IRAZ datasheet(16/48 Pages) RENESAS

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ISL68127

FN8748 Rev.2.00

Page 16 of 48

Jul 12, 2019

Lossless Input Current and Power Sensing

Input current telemetry is provided through an input current

synthesizer. By using the IC’s ability to precisely determine its

operational conditions, the input current can be synthesized to a

high degree of accuracy without the need for a lossy sense

resistor. You can fine-tune offset and gain in PowerNavigator.

Note that input current sense must be fine-tuned after the output

current sense setup is finalized. You can calculate input power

with a precise knowledge of input current and voltage.

Input current and power telemetry is accessed through PMBus

and easily monitored in PowerNavigator. VIN is monitored directly

by the VINSEN pin through a 1:5 resistor divider as shown in

Figure 17.

Voltage Regulation

The remote sense amplifier senses and digitizes the output

voltage. After digitization, the regulation loop is entirely digital.

The ISL68127 uses traditional PID controls and 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), which is accomplished using current feedback.

For applications requiring droop regulation, specify the output

resistance in PowerNavigator.

Current feedback stability benefits are available for rails that do

not specify droop regulation, such as system agent. For these

applications, you can enable AC current feedback in

PowerNavigator. With this configuration, the DC output voltage is

steady regardless of load current.

Power-On Reset (POR)

ISL68127 initialization 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 loads 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, you can monitor

VIN determine when it exceeds its user-programmable rising

UVLO threshold. When VCC and VIN satisfy their respective

voltage conditions, the controller is in its shutdown mode. The

controller transitions to its active state and begins soft-start

when the EN0/EN1 command is at start-up. 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 may 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, you can 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 ISL68127 provides 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.

Use PowerNavigator to configure the soft-start delay and

ramp-up/down times. 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.

Renesas recommends setting the ramps to a non-zero value to

prevent inadvertent fault conditions due to excessive inrush

current.

Stored Configuration Selection

You can store and use up to eight configurations at any time

using the on-board nonvolatile memory. Configurations are

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

device loads the configuration indicated by the 1% resistor value

detected on the CONFIG pin. Resistor values indicate use of one

of the eight possible configurations. See Table 3 for 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.

For example, a configuration with the identifier 0 can be saved

eight times, or configurations with all eight identifiers can be

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

PowerNavigator provides a simple interface to save and load

configurations.

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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