RT3606BC datasheet(45/72 Pages) RICHTEK

45 / 72 page

RT3606BC

DS3606BC-04 June 2016

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Ramp Compensation

The G-NAVPTM topology is one type of ripple based control

that has fast transient response and can lower BOM cost.

However, ripple based control usually has poor noise

immunity. RT3606BC provides the ramp compensation to

increase noise immunity and reduce jitter at the switching

node. Figure 21 shows the ramp compensation.

Noise Margin

VCOMP

Noise Margin

IMON-VREF

w/o ramp compensation

w/ ramp compensation

IMON-VREF

VCOMP

Figure 21. Ramp Compensation

For the RT3606BC, the ramp compensation also needs

to be considered during mode transition from PS0/1 to

PS2. For achieving smooth mode transition into PS2, a

proper ramp compensation design is necessary. Since

the ramp compensation needs to be proportional to the

on-time, then RAMP is set as

Quick Response (QR) Mechanism

When the transient load step-up becomes quite large, it

is difficult for loop response to meet the energy transfer.

Hence, that output voltage generate undershoot to fail

specification. The RT3606BC has Quick Response (QR)

mechanism being able to improve this issue. It adopts a

nonlinear control mechanism which can disable

interleaving function and simultaneously turn on all UGATE

one pulse at instantaneous step-up transient load to

restrain the output voltage drooping, Figure 22 shows the

QR behavior.

QR Threshold

QR Width

PWM1

PWM2

PWM3

VCORE

Load

Figure 22. Quick Response Mechanism

The output voltage signal behavior needs to be detected

so that QR mechanism can be trigged. The output voltage

signal is via a remote sense line to connect at VSEN pin

that is shown in Figure 23. The QR mechanism needs to

set QR width and QR threshold. Both definitions are shown

in Figure 22.Aproper QR mechanism set can meet different

applications. SET2 can set QR threshold and QR width

by internal current source 80

μA with multi-function pin

setting mechanism.

Figure 23. Simplified QR Trigger Schematic

For example, QR threshold 20mV/10mV at PS0/PS1 and

2.22 x TON QR width are set. According to the Table 8,

the set voltage should be between 0.4505V and 0.4723V.

Please note that a high accuracy resistor is needed for

this setting accuracy, < 1% error tolerance is

recommended. In the Table 8, there are some “NA” marks

in QRWIDTH section. It means that users should not use

it to avoid the possibility of shift digital code due to

tolerance concern.

133%

400k



VSEN

QR Pulse

Generation

Circuit

CMP

QR_width

QR_TH

RT3606BC 데이터시트(PDF) 45 Page - Richtek Technology Corporation

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