IR36021 datasheet(24/41 Pages) IRF

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IR36021

DIGITAL POL BUCK CONTROLLER with I2C AND PMBus

Interface

February 27, 2013 | Rev 3.5

load (and with low‐side MOSFETs being off) it can take a

relatively long time for the output voltage to decay down

to the steady state value.

Note that ATA is more effective on multi‐phase rails (e.g.

loop1) and when used in conjunction with the load‐line.

Figure 25: Vout1 (2phase) response to a transient. ATA

Enable/Disable Comparison, load‐line is enabled.

Figure 26: ATA close up when a load is applied.

DYNAMIC VID SLEW RATE

VID refers to the code inside a register which corresponds

to a specific output voltage. This code can be changed in

the GUI by changing the manual_VID registers (through I2C

communication) or by corresponding commands (for

example margining commands) sent through PMBus. The

IR36021 provides the VR designer with up to 8 slew rates

by selecting a slew rate setting as shown in the fast‐rate

column in Table 2.

Figure 27: Diode Emulation (ATA is on) during a load release

EFFICIENCY SHAPING

IR36021 features Efficiency Shaping Technology that

enables VR designers to cost‐effectively maximize system

efficiency. Efficiency Shaping Technology consists of phase‐

shedding (sometimes referred to as ‘Dynamic Phase

Control’, DPC) and diode‐emulation to achieve the best VR

efficiency at a given cost point.

POWER‐SAVING STATES

The IR36021 can be programmed to do phase shedding for

loop1 and/or go into diode emulation at light load for both

loops. Both of these mechanisms improve efficiency at

light loads at the expense of more output voltage ripple.

Phase‐shedding

and

diode‐emulation

can

enabled/disabled independently from each other and

independently for each loop. To improve efficiency for

loop1 at light loads when there is no transient, it is

recommended to program the device to do phase

shedding at about 20A and as the current decreases to

about 3‐5A the diode‐emulation should be activated for

the running phase (phase‐1a). This sequence can be

explained using Power States as summarized in Table 9.

For loop2, since it is 1phase, PS1 and PS0 are identical.

When there are transients, it is recommended to use

either phase shedding or diode emulation since using both

mechanisms can further increase the output voltage ripple

in some conditions.

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