RichTek RT8800, RT8800B Manual

LNK305

RT8800/B

General Purpose 2/3-Phase PWM Controller

for High-density Power Supply

General Description

The RT8800/B are general purpose multi-phase synchronous buck controllers dedicating for high density power supply regulation. The parts implement 2, and 3 buck switching stages operating in interleaved phase set automatically. The output voltage is regulated and controlled following the input voltage of FB pin. With such a single analog control, the RT8800/B provide a simple, flexible, wide-range and extreme cost-effective highdensity voltage regulation solutions for various high-density power supply application. The RT8800/B multi-phase architecture provide high output current while maintaining low power dissipation on power devices and low stress on input and output capacitors. The high equivalent operating frequency also reduces the component dimension and the output voltage ripple in load transient.

RT8800/B implement both voltage and current loops to achieve good regulation, response and power stage thermal balance. The RT8800/B apply the time sharing DCR current sensing technology newly as well; with such a topology, the RT8800/B extract the DCR of output inductor as sense component to deliver a more precise load line regulation and better thermal balance capability. Moreover, the parts monitor the output voltage for overcurrent and over-voltage protection; Soft-start and programmable under-voltage lockout are also provided to assure the safety of power system.

Applications

Desktop CPU core power

Low Output Voltage, High power density DC-DC

Converters

Voltage Regulator Modules

Marking Information

For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail.

Features

5V Power Supply Voltage

2/3-Phase Power Conversion with Automatic Phase Selection (RT8800 : 2/3-Phase, RT8800B : 2-Phase) Output Voltage Controlled by External Reference Voltage

Precise Core Voltage Regulation

Power Stage Thermal Balance by DCR Current Sensing

Extreme Low-Cost, Lossless Time Sharing Current Sensing

Internal Soft-start

Hiccup Mode Over-Current Protection Over-Voltage Protection

Adjustable Operating Frequency and Typical at 300kHz Per Phase

Power Good indication

Small 16-Lead VQFN Package (For RT8800 only) RoHS Compliant and 100% Lead (Pb)-Free

Ordering Information

RT8800/B

Package Type

QV : VQFN-16L 3x3 (Pb Free Only)

S : SOP-16

Operating Temperature Range C : Commercial Standard

P : Pb Free with Commercial Standard

2-Phase 2/3-Phase

Note :

VQFN-16L 3x3 is in V-Type RichTek Pb-free products are :

`RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

`Suitable for use in SnPb or Pb-free soldering processes. `100% matte tin (Sn) plating.

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	RT8800/B
	Pin Configurations						(TOP VIEW)
		VDD	PWM3	PWM2	PWM1
		16	15 14		13		VDD		16	PWM2
	DACFB	1			12	ISP1	DACFB	2	15	PWM1
	DACQ	2	GND		11	ISP2	DACQ	3	14	N/C
	FB	3			10	ISP3	FB	4	13	ISP1
	DVD	4			9	PGOOD	DVD	5	12	ISP2
		5	6	7	8		COMP	6	11	PGOOD
							PI	7	10	GND
		COMP	PI	RT	ICOMMON
							RT	8	9	ICOMMON
		VQFN-16L 3x3						SOP-16
								RT8800B

RT8800

Functional Pin Description

DACFB

Negative input of internal buffer amplifier for reference voltage regulation. The pin voltage is locked at internal VREF = 0.8V by properly close the buffer amplifier feedback loop.

DACQ

The pin is defined as the output of internal buffer amplifier for reference voltage regulation.

FB

The pin is defined as the inverting input of internal error amplifier.

DVD

The pin is defined as a programmable power UVLO detection input. Trip threshold = 0.8V at VDVD rising.

COMP

The pin is defined as the output of the error amplifier and the input of all PWM comparators.

PI

The pin is defined as the positive input of the error amplifier.

RT

Switching frequency setting. Connect this pin to GND with a resistor to set the frequency.

ICOMMON

Common negative input of current sense amplifiers for all three channels.

PGOOD

Output power-good indication. The signal is implemented as an output signal with open-drain type.

ISP1 , ISP2 , ISP3

Current sense positive inputs for individual converter channel current sense.

PWM1 , PWM2 , PWM3

PWM outputs for each phase switching drive.

VDD

Chip power supply. Connect this pin to a 5V supply.

GND

Chip power ground.

Exposed Pad (RT8800)

Exposed pad should be soldered to PCB board and connected to GND.

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2

RT8800/B

Typical Application Circuit

(Note : The inductor’ s DCR value must be large than 0.3mΩ

: X7R/R-type capacitor is required for all time constant setting capacitor of DCR sensing.)

CORE

C29 x 12

10uF

C33

12V

V

C18to 1000uF

4

C30

x

to

C13 1000uF

2200uF1uF

0.5uH

Q2

Q3 C14 .3nF3

C15C16 2200uF

Q4

0.5uH

R26 Q5

Q6C17 3.3nF

1uH

C11

L1

L2

PHASE1

L3

C12

R25 2.2

1uF

PHASE2

2.2

Q1

PHB83N03LT

PHB95N03LT

PHB83N03LT

PHB95N03LT

C9 1uF

R21 0

R22

0

R23

0

R24

0

12

13

4

9

8

7

D1

SS12/SM

11

BOOT1

UGATE1

PHASE1

RT9602

LGATE1

UGATE2

PHASE2

LGATE2

BOOT2

10

D2 C10

1uF

VDD

PVCC

PWM1

PWM2

GND

PGND

SS12/SM

14

5

1

2

3

6

R20 10

C8 1uF

PHASE2

PHASE1

C7 1uF

16 0

R

R

ICOMMON1

12V

R16 0

R17

10

12

13Optional

C5

R19

CORE

R18

1uF

C6

C4

15

PWM1 PWM2

GND

ISP2

ISP1

1uF

Optional

430

R

V

5V

C3

1

COMP

RT8800B

DVD

5

R15 16k

ICOMMON2

VDD

ICOMMON

9

Optional R

forOptional C&R

R2

3kR3

4

FB

PI

DACQ

DACFB

PGOOD

RT

8

R13

6

R14

3k

27k

C2

10nF

7

3

2

11 R12

DROOP

1.8k

C1 33pF

R11

10k

3.3V 5.1k

12V

R1 15k

110k R 56k

27k

13k

6.8k

3.3k

R4

R5

R6

R7

R8

R9

R10

VID5

VID0

VID1

VID2

VID3

VID4

Figure A. 2-phase with resistive DAC

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	3

com.richtek.www 4

or name brand All	Figure
belong trademark	with phase-3 .B
respectively owner their to 04-DS8800/B	DAC resistive
November
2005

PHASE2

RT8800/B

L1

0.5uH

12V

VIN

R19

2.2

C163.3uF

Q3

1uH

Q1

Q2

C8

C9

D1

1000uF

1uF

C15

C1

Optional

5V

C10 to C13

C14

1uF

R20

C24 to C35

33pF

R2

C2

R18

12V

C4

1500uF x 4

1uF

0

1000uF x 12

0

4.7uF

21

17

19

20

3

16

13

R1

5

3

UGATE2

PHASE2

PVCC2

LGATE2

NC

0

Q7

PHASE3

10uF x 4

15k

C3

C23

10nF

R25

3.3nF

C36 to C39

16 BOOT2

14

VID5

RDROOP 6

COMP

FB

VDD

PWM1

RT9605

LGATE3

1uF

Q8

7 PWM3

PVCC3

15

R27

R4

110k

R5

56k

PI

PWM3

15

2.2

L2

VID0

R6

27k

2 DACQ

RT8800

5 PWM2

GND

PHASE3 11 12V

R26

0.5uH

VCORE

VID1

R11

GND

PWM2 14

4 PWM1

UGATE3 10

Q9

R7

13k

1.8k

ISP3 10

0

VID2

1 DACFB

2

9

D3

R8

6.8k

R16

PHASE3

BOOT1

BOOT3

C22

VID3

9

DVD

RT

ICOMMON

ISP1

Optional

PVCC1

LGATE1

UGATE1

PHASE1

VDD

1uF

PGOOD

ISP2 11

R9

3.3k

R12

C5 1uF

R

12V

VIN

VID4

10k

R10

5.1k

3.3V

27k

12

Optional

R17

PHASE2

1

24

22

23

8 R23 10

R13

4

7

8

5VSB

12V

C6

R

C17

R21

12V

R22

PHASE1

R15

C18

R14

1uF

0

16k

1uF

0

C19 1uF

3k

1uF

R17

L3

Optional

PHASE1

D2

0.5uH

430

R

Q4

Q5

Optional

RICOMMON1

C7

R24

RICOMMON2

1uF

12V

VIN

2.2

C20

Q6

VCORE

3.3nF

04-DS8800/B

November

PHASE2

L1

2005

All

0.5uH

12V

R14

2.2

C16

VIN

3.3uF

Q3

trademarkornamebrand

withphase-3.CFigure

6 PI

5 COMP

3 FB

VDD

13PWM1

1uH

PHASE2

LGATE2

R22

L2

Q1

Q2

C9

C10

D1

1000uF

1uF

C17

C1

Optional

5V

C11 to C14

1uF

R15

C25 to C36

33pF

R2

C3

C5

C15

R13

12V

1500uF x 4

1uF

0

0

1000uF x 12

4.7uF

21

17

19

20

3

16

R20

10uF x 4

UGATE2

PVCC2

NC

Q7

R1

C2

R3 3k

C24

PHASE3

15k

10nF

3.3nF

C37 to C40

16 BOOT2

LGATE3

14

0

Q8

RT9605

C22

7 PWM3

PVCC3 15

respectivelyownertheirtobelong

generatorDACRT9401A/B

RDROOP

8

PWM3 15

1uF

2.2

5 PWM2

11 12V

0.5uH

C4

2

DACQ

RT8800

GND

PHASE3

R21

10nF

R4

PWM2

14

4 PWM1

UGATE3 10

VCORE

GND

0

Q9

5.1k

1

DACFB

ISP3

10

R10

2

9

R5

BOOT1

BOOT3

PHASE3

3.3V

9

DVD

RT

ICOMMON

ISP1

11

Optional

PVCC1

LGATE1

C23

5.1k

UGATE1

PHASE1

VDD

R6

C6 1uF

R

12V

VIN

10k

R7 27k

4

7

12

Optional

R11

PHASE2

1

24

22

23

8 R19 10

5VSB

12V

uF

R

C18

R16

12V

R18

PHASE1

R8

R9

C7

1uF

0

C19

1

0

C20 1uF

RT9401A/B

3k

16k

R12

1uF

1

PHASE1

L3

VID3 8

Optional

D2

VID2

0.5uH

430

R

Q4

Q5

2

VID4 7

RICOMMON1

VID1

Optional

C8

VIN

3

GND 6

RICOMMON2

1uF

12V

R17 2.2

C21

Q6

com.richtek.www

VDA

VCORE

3.3nF

RT8800/B

5

5V

4

VDD

VID0 5

RT8800/B

Function Block Diagram

PWM1

PWM2

PWM3

ICOMMON

ISP1

ISP2

ISP3

PWM Logic

& Driver

PWM Logic

& Driver

PWM Logic

& Driver

Mux

-

GM+

INH

PWMCP

INH

PWMCP

INH

PWMCP

Mux

+

-

-

+

-

Sample & Hold

Sample & Hold

Sample & Hold

+

++

+

+

+

+

+

+

+

GND

RT

Oscillator

&

Ramp Generator

OCP

SUM/N

& OCP Detection

EA

MAJ

PGOOD VDD DVD

Power On Reset

Soft Start

-+OVP

0.8V

REF

V

500mV

+ - Buffer Amplifier

COMP

FB PI

DACQ

DACFB

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									RT8800/B
						Table. Output Voltage Program
	VID5		VID4		VID3	VID2	VID1	VID0	Nominal Output Voltage (V)
	1		1		1	1	1	1	1.0800
	1		1		1	1	1	0	1.1000
	0		1		1	1	1	0	1.1125
	1		1		1	1	0	1	1.1250
	0		1		1	1	0	1	1.1375
	1		1		1	1	0	0	1.1500
	0		1		1	1	0	0	1.1625
	1		1		1	0	1	1	1.1750
	0		1		1	0	1	1	1.1875
	1		1		1	0	1	0	1.2000
	0		1		1	0	1	0	1.2125
	1		1		1	0	0	1	1.2250
	0		1		1	0	0	1	1.2375
	1		1		1	0	0	0	1.2500
	0		1		1	0	0	0	1.2625
	1		1		0	1	1	1	1.2750
	0		1		0	1	1	1	1.2875
	1		1		0	1	1	0	1.3000
	0		1		0	1	1	0	1.3125
	1		1		0	1	0	1	1.3250
	0		1		0	1	0	1	1.3375
	1		1		0	1	0	0	1.3500
	0		1		0	1	0	0	1.3625
	1		1		0	0	1	1	1.3750
	0		1		0	0	1	1	1.3875
	1		1		0	0	1	0	1.4000
	0		1		0	0	1	0	1.4125
	1		1		0	0	0	1	1.4250
	0		1		0	0	0	1	1.4375
	1		1		0	0	0	0	1.4500
	0		1		0	0	0	0	1.4625
	1		0		1	1	1	1	1.4750
	0		0		1	1	1	1	1.4875
	1		0		1	1	1	0	1.5000
	0		0		1	1	1	0	1.5125
	1		0		1	1	0	1	1.5250
	0		0		1	1	0	1	1.5375
	1		0		1	1	0	0	1.5500
									To be continued
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RT8800/B

Table. Output Voltage Program

VID5	VID4	VID3	VID2	VID1	VID0	Nominal Output Voltage (V)
0	0	1	1	0	0	1.5625
1	0	1	0	1	1	1.5750
0	0	1	0	1	1	1.5875
1	0	1	0	1	0	1.6000
1	0	1	0	0	1	1.6250
1	0	1	0	0	0	1.6500
1	0	0	1	1	1	1.6750
1	0	0	1	1	0	1.7000
1	0	0	1	0	1	1.7250
1	0	0	1	0	0	1.7500
1	0	0	0	1	1	1.7750
1	0	0	0	1	0	1.8000
1	0	0	0	0	1	1.8250
1	0	0	0	0	0	1.8500

Note: 1 : Open

0 : VSS or GND

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