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UP6204

Compact Three-Phase Synchronous-Rectified Buck Controller

Unspecified 

Preliminary

uP6204

Functional Description

The uP6204 is a compact three-phase synchronous-rectified

Buck controller specifically designed to deliver high quality

output voltage for high power applications. This part is

capable of delivering up to 90A output current thanks to its

embedded bootstrapped drivers that support 12V + 12V

driving capability. The built-in bootstrap diode simplifies the

circuit design and reduces external part count and PCB

space.

The output voltage is precisely regulated to the reference

inputs R1/R2/R3/R4 that are selected by VID inputs VID1

and VID0. The reference voltage can also be programmed

by I2C interface.

The uP6204 adopts DCR current sensing technique for over

current protection and droop tuning. Current balance is

achieved by sensing the phase current through RDS(ON) of

lower MOSFET when it turns on.

This part features comprehensive protection functions

including over current protection, input/output under voltage

protection, over voltage protection and over temperature

protection.

Other features include adjustable soft start, adjustable

operation frequency, and quick response to step load

transient. With aforementioned functions, this part provides

customers a compact, high efficiency, well-protected and

cost-effective solutions. This part comes to VQFN6x6-40L

package.

VIN1

VOUT

VIN2

PWM Controller

Figure 1. Simplified Two-Phase Buck Converter.

The uP6204 selects phase number of operation according

to the MODE pin and VCC2 status. The MODE pin is a tri-

state input. When the MODE pin is pulled low, the uP6204

operates in three phases. When the MODE pin is left

floating, only phase 1 is activated. When the MODE pin is

pulled high, only phase 1 & 2 are activated. The uP6204

does not support real-time phase number of operation

change. If any change of MODE state has been detected,

the uP6204 will shut down the output voltage and re-soft-

start again.

Table 1. Phase Number of Operation Table.

MODE VCC2 POR Phase Number of Operation

High

X

Phase 1 /2

Selecting Phase Number of Operation

The uP6204 supports single/two/three-phase operation that

is important for PCIE interfaced graphic cards where neither

bus power nor external power is capable of delivering full

load current. Take a two-phase buck converter as shown in

Figure 1 for example. Two-phase operation will make the

phase 2 converter act like a boost converter if the external

power is not available, boosting the output voltage V to

OUT

the input voltage VIN2. The relationship between input voltage

and output voltage is governed by conventional boost

converter equation. Offset of the current balance function

may make the duty cycle of phase 2 converter smaller

than that of phase 1 converter. This results in input voltage

V higher than 15V that may damage the input capacitors

IN2

and other devices. Therefore, phase 2 must be turned off

when input voltage VIN2 is not present to eliminate the

possibility of over voltage on input capacitors and other

devices of the phase 2 converter.

Floating

Low

Low

X

Phase 1

YES

Phase 1/2/3

NO

Shutdown

VCC1 powers the gate drives for phase 1/2 while VCC2

powers the gate drivers for phase 1. When MODE pin is

pulled low, the uP6204 checks the VCC2 POR status before

soft start to ensure both bus and external power inputs are

ready for providing current to output voltage. The VCC2 pin

should be connected to VIN2 (external power input). Figure

2 shows an implementation example where phase 1/2 are

powered by PECI bus and phase 3 is power by external

cable.

Note that when operated in single/dual-phase, the

rated current is reduced to fractions of normal level.

Continuous demanding high current may damage the

converter.

uPI Semiconductor Corp., http://www.upi-semi.com

6

Rev. P01, File Name: uP6204-DS-P0100

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