ISL68137IRAZ datasheet(13/54 Pages) RENESAS

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ISL68137

FN8757 Rev.1.00

Page 13 of 54

Jun 26, 2017

Functional Description

Overview

The ISL68137 is a digital dual output 7-phase PWM controller

that can be programmed for single output 7+0, dual output 6+1,

5+2, or 4+3 phase operation. Operation using less than seven

phases between two outputs is also supported. Existing digital

multiphase solutions use analog comparator based schemes

(nonlinear) to bolster the inadequate transient response

common to many digital multiphase solutions. The ISL68137

uses a linear voltage regulation scheme to address transient

loads. As a result, it is much easier for users to configure and

validate their designs when compared with nonlinear schemes.

By combining a proprietary low noise and zero latency digital

current sense scheme with cutting edge digital design

techniques, Intersil is able to meet transient demands without

resorting to nonlinear schemes. In addition, the ISL68137 can

store up to eight user configurations in NVM and allows the user

to select the desired configuration through pin-strap (CONFIG).

The result is a system that is easy to configure and deploy.

The ISL68137 supports several performance enhancing features.

These include AVSBus control, diode braking, automatic phase

dropping, DCR/resistor/smart power stage current sense

support, load line regulation, and multiple temperature sensing

options.

To facilitate configuration development, the PowerNavigator GUI

provides a step-by-step arrangement for setup and parametric

adjustment. After a configuration has been set, the user can

employ PowerNavigator to monitor telemetry or use the PMBus

interface directly based on the supported command set.

PWM Modulation Scheme

The ISL68137 uses Intersil's proprietary linear synthetic current

modulation scheme to improve transient performance. This is a

unique constant frequency, dual edge PWM modulation scheme

with both PWM leading and trailing edges being independently

moved to give the best response to transient loads. Current

balance is an inherent part of the regulation scheme. The

modulation scheme is capable of overlapping pulses if the load

profile demands such operation. In addition, the modulator is

capable of adding or removing pulses from a given cycle in

response to regulation demands while still managing maximum

average frequency to safe levels. For DC load conditions the

operating frequency is constant.

PMBus Address Selection

When communicating with multiple PMBus devices on a single

bus, each device must have its own unique address so the host

can distinguish between the devices. The device address can be

set using a 1% resistor on the SA pin according to the pin-strap

options listed in Table 2.

Phase Configuration

The ISL68137 supports up to two regulated outputs through

seven configurable phases. Either output is capable of controlling

up to seven phases in any arbitrary mix. Phase assignments are

accomplished through the PowerNavigator GUI.

Although the device supports arbitrary phase assignment, it is

good practice to assign phases to Output 1 in descending

sequential numerical order starting from Phase 6. For example, a

4-phase rail could consist of phases 6, 5, 4, and 3. For Output 0,

phases would be assigned starting from Phase 0 in ascending

sequential numerical order.

Automatic Phase Add and Drop

To produce the most optimal efficiency across a wide range of

output loading, the modulator supports automatic dropping or

adding of phases. Use of automatic phase dropping is optional. If

automatic phase dropping is enabled, the number of active

phases at any time is determined solely by load current. During

operation, phases of Output 1 will drop beginning with the lowest

phase number assigned. Phase dropping begins with the highest

assigned phase number. Figure 8 illustrates the typical

characteristic of efficiency vs load current vs phase count.

TABLE 2. RESISTOR VALUES TO ADDRESS MAPPING

R SA

(Ω)

PMBus

ADDRESS

R SA

(Ω)

PMBus

ADDRESS

60h

1500

50h

180

61h

1800

51h

330

64h

2200

54h

470

65h

2700

55h

680

40h

3300

58h

820

41h

3900

59h

1000

44h

4700

5Ch

1200

45h

5600

5Dh

LOAD (A)

FIGURE 8. EFFICIENCY vs PHASE NUMBER

100

120

140

160

180

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