RT3607CE datasheet(32/69 Pages) RICHTEK

32 / 69 page

RT3607CE

www.richtek.com

DS3607CE-01 June 2016

is a registered trademark of Richtek Technology Corporation.

Figure 9. POR Detection

Figure 10. Timing Chart for POR Process

Core VR

Phase Disable (Before POR)

The number of active phases is determined by the internal

circuitry that monitors the ISENxN voltages during startup.

Normally, the VR operates as a 4-phase PWM controller.

Pulling ISEN4N to VCC programs a 3-phase operation,

pulling ISEN3N and ISEN4N to VCC programs a 2-phase

operation, and pulling ISEN2N, ISEN3N and ISEN4N to

VCC programs a 1-phase operation. Before POR, VR

detects whether the voltages of ISEN2N, ISEN3N and

ISEN4N are higher than “VCC

− 1V”, respectively to

decide how many phases should be active. Phase

selection is only active during POR. When POR = high,

the number of active phases is determined and latched.

The unused ISENxP pins are recommended to be

connected to VCC and unused PWM pins can be left

floating.

Switching Frequency Setting

The RT3607CE is one kind of constant on-time control.

The patented CCRCOT (Constant Current Ripple COT)

technology can generate an adaptive on-time, the on-time

will vary with the input voltage and VID code to obtain a

constant current ripple, so that the output voltage ripple

can be controlled nearly like a constant as different input

and output voltages change.

For Core VR, connect a resistor RTON between input

terminal and the TONSET pin to set the on-time width.

TON

DAC

TON

DAC

4.73p 1.2

T(V

1.2)

R4.73p V

T(V

1.2)













For better efficiency of the given load range, the maximum

switching frequency is suggested to be :



SW(MAX)

ON_LS,max

ON_HS,max

ON_LS,max

IN(MAX)

ON,VAR

IccTDC

VID1

DCR

N R

IccTDC









 













































where FSW(MAX) is the maximum switching frequency, VID1

is the typical VID of application, VIN(MAX) is the maximum

application input voltage, IccTDC is the thermal design

current of application, N is the phase number. The

RON_HS,max is the maximum equivalent high-side RDS(ON) ,

and nHS is the number of high-side MOSFETs ; RON_LS,max

is the maximum equivalent low-side RDS(ON), and nLS is

the number of low-side MOSFETs. TD is the summation

of the high-side MOSFET delay time and the rising time,

TON, VAR is the TON variation value. DCR is the inductor

DCR, and RLL is the loadline setting. In addition, Richtek

provides a Microsoft Excel-based spreadsheet to help

design the RTON for RT3607CE.

When load increases, on-time keeps constant. The off-

time width will be reduced so that loading can load more

power from input terminal to regulate output voltage.

Hence, the loading current usually increases in case the

switching frequency also increases. Higher switching

frequency operation can reduce power components' size

and PCB space, trading off the whole efficiency since

switching related loss increases, vice versa.

VCC

DVD

POR

SVID Invalid

Invalid

Valid

2ms

POR

Chip

Enable

4.34V

0.7V

VCC

DVD

VTT

1.05V

VIN 5V

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