Richtek RT8805CGQV, RT8805CGQVA, RT8805CPQV, RT8805CPQVA Schematic [ru]

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Preliminary

RT8805C

Two Phase General Purpose PWM Controller

General Description

The RT8805C is the most compact dual-phase synchronous buck controller in the industry specifically designed for high power density applications. This part is capable of delivering up to 60A output current due to its embedded bootstrapped drivers that support 12V + 12V driving capability.

The phase currents are sensed by innovative time sharing RDS(ON) current sensing technique for current balance and over current balance. Using one common GM amplifier to sense two phase currents eliminates offset and nonlinearity of the GM amplifier and yields good current balance. Other features include adjustable operation frequency from 50kHz to 1MHz, adjustable soft-start, PGOOD, external compensation, enable/shutdown for various application and performance consideration.

The RT8805C comes to a tiny footprint package of VQFN-16L 3x3 package that is capable of dissipating up to 1.47W heat.

Ordering Information

RT8805C

Package Type

QV : VQFN-16L 3x3 (V-Type)

Operating Temperature Range

P : Pb Free with Commercial Standard

Note :

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.

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

z12V Power Supply Voltage

z2 Phase Power Conversion

zEmbedded 12V Boot Strapped Driver

zPrecise Core Voltage Regulation

zLow Side MOSFET RDS(ON) Current Sensing for Power Stage Current Balance

zExternal Compensation

zAdjustable Soft-Start

zAdjustable Frequency and Typical at 300kHz Per Phase

zPower Good Indication

zAdjustable Over Current Protection

zSmall 16-Lead VQFN Package

zRoHS Compliant and 100% Lead (Pb)-Free

Applications

zMiddle-High End GPU Core Power

zHigh End Desktop PC Memory Core Power

zLow Output Voltage, High Power Density DC-DC Converters

zVoltage Regulator Modules

Pin Configurations

(TOP VIEW)

 

PHASE1

LGATE1

VCC

LGATE2

 

 

16

15

14

13

 

UGATE1

1

 

 

12

PHASE2

BOOT1

2

GND

11

UGATE2

AGND

3

10

BOOT2

 

 

IMAX

4

 

 

9

PGOOD

 

5

6

7

8

 

 

RT

SS

COMP

FB

 

 

VQFN-16L 3x3

 

DS8805C-01 November 2005

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1

Richtek RT8805CGQV, RT8805CGQVA, RT8805CPQV, RT8805CPQVA Schematic

RT8805C

Preliminary

Typical Application Circuit

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

 

R8

9

RT8805C

2

 

C5

3.3VCC

 

PGOOD

BOOT1

 

 

 

R9

 

 

12VCC

 

14

VCC

 

 

C4

 

 

 

UGATE1

1

 

 

 

 

C9

 

Q1

 

 

 

R1

5

RT

PHASE1

16

 

L1

 

 

R2

 

VOUT

 

 

4

IMAX

 

15

 

 

 

 

 

LGATE1

Q2

 

 

 

 

3

AGND

 

 

 

 

 

 

 

C8

 

 

 

8

 

 

10

 

 

 

C1

FB

BOOT2

 

 

 

 

 

 

 

 

 

7

 

 

 

 

 

COMP

 

 

 

 

C2

 

 

11

C6

C7

 

R3

 

 

UGATE2

Q3

 

 

 

6

 

PHASE2

12

 

L2

 

 

 

SS

 

 

 

 

 

 

 

 

 

 

EN

Q5

C3

 

GND

LGATE2

13

Q4

R4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R5

Function Block Diagram

 

 

 

 

 

VCC

 

BOOT1

 

 

 

PWMCP

 

 

 

UGATE1

PGOOD

 

 

-

PWM1

 

 

PHASE1

 

 

+

 

 

 

 

 

Logic

 

 

VCC

0.8V

+

 

 

 

 

 

LGATE1

FB

-EA

 

 

 

VCC

 

BOOT2

COMP

 

 

 

 

 

 

External

 

PWMCP

 

 

 

UGATE2

 

 

+

PWM2

 

 

PHASE2

 

Soft Star

 

 

 

 

 

-

Logic

 

 

 

 

 

 

 

VCC

SS

 

 

 

 

 

 

LGATE2

 

CLK1

RAMP1 RAMP2

CLK2

 

 

 

 

AGND

 

Current

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Balance

 

-

MUX

PHASE2

 

 

 

S/H

PHASE1

 

 

 

GM

 

 

IMAX

 

OCP

 

+

 

 

 

 

 

 

 

To PWM Logic

 

 

 

 

 

 

VCC

Reg

OC

 

 

 

 

 

VDD

 

 

 

 

Central

 

 

 

 

PGOOD

 

 

 

 

 

 

Logic

 

 

CLK1

 

 

 

 

RT

Clock

 

 

 

 

 

CLK2

 

 

 

 

 

 

 

 

 

 

 

OC

 

 

 

 

 

 

 

 

 

GND

 

 

 

 

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DS8805C-01 November 2005

2

Preliminary

RT8805C

Functional Pin Description

UGATE1 (Pin 1), UGATE2 (Pin 11)

UpperGateDrive. These pins drive the gates of the highside MOSFETs.

BOOT1 (Pin 2), BOOT2 (Pin 10)

Bootstrap Power Pin. These pins power the high-side MOSFET drivers. Connect These pins to the junctions of the bootstrap capacitors.

AGND (Pin 3)

Chip Analog Ground.

IMAX (Pin 4)

Maximum Current Setting. This pin sets the current limiting level. Connect this pin with resistor to ground to set the current limit.

RT (Pin 5)

Timing Resistor. Connect a resistor from RT to AGND to set the clock frequency.

SS (Pin 6)

Soft-Start Pin. This pin provides soft-start function for controller. The COMP voltage of the converter follows the ramping voltage on the SS pin.

COMP (Pin 7)

Compensation Pin. This pin is output node of the error amplifier.

FB (Pin 8)

Feedback Pin. This pin is negative input pin of the error amplifier.

PGOOD (Pin 9)

Power Good. PGOOD is an open drain output used to indicate the status of the voltages on SS pin and FB pin. PGOOD will go high impedance when SS > 3.7V and FB > 0.6V.

LGATE1 (Pin 15), LGATE2 (Pin 13)

Lower Gate Drive. These pins drive the gate of the lowside MOSFETs.

PHASE1 (Pin 16), PHASE2 (Pin 12)

These pins are return nodes of the high-side driver. Connect These pins to high-side MOSFET sources together with the low-side MOSFET drains and the inductors.

VCC (Pin 14)

The VCC pin is the external 12V power. Internal 5V power (VDD) is regulated from this pin. This pin also powers the low side MOSFETS drivers.

GND (Exposed Pad)

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

DS8805C-01 November 2005

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3

RT8805C

Preliminary

Absolute Maximum Ratings

(Note 1)

z Supply Voltage, VCC --------------------------------------------------------------------------------------------------

−0.3V to 16V

z PHASE to GND

 

DC -------------------------------------------------------------------------------------------------------------------------

−5V to 15V

< 200ns ------------------------------------------------------------------------------------------------------------------

−10V to 30V

z BOOT to PHASE ------------------------------------------------------------------------------------------------------

15V

z BOOT to GND

 

DC -------------------------------------------------------------------------------------------------------------------------

−0.3V to VCC+15V

< 200ns ------------------------------------------------------------------------------------------------------------------

−0.3V to 42V

z Input, Output or I/O Voltage -----------------------------------------------------------------------------------------

GND-0.3V to 7V

z Power Dissipation, PD @ TA = 25°C

 

VQFN−16L 3x3 ---------------------------------------------------------------------------------------------------------

1.47W

z Package Thermal Resistance (Note 4)

 

VQFN−16L 3x3, θJA ---------------------------------------------------------------------------------------------------

68°C/W

z Junction Temperature -------------------------------------------------------------------------------------------------

150°C

z Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------

260°C

z ESD Susceptibility (Note 2)

 

HBM (Human Body Mode) ------------------------------------------------------------------------------------------

1.5kV

MM (Machine Mode) --------------------------------------------------------------------------------------------------

200V

Recommended Operating Conditions (Note 3)

z Supply Voltage ---------------------------------------------------------------------------------------------------------

9V to 14V

z Junction Temperature Range ----------------------------------------------------------------------------------------

−20°C to 70°C

Electrical Characteristics

(VIN = 12V, TA = 25°C, unless otherwise specified)

Parameter

Symbol

Test Conditions

Min

Typ

Max

Units

Supply Input

 

 

 

 

 

 

 

Power Supply Voltage

VCC

 

--

12

15

 

V

 

 

 

 

 

 

 

 

Power On Reset

VCC

 

5.4

5.9

6.5

 

V

Power On Reset Hysteresis

 

 

--

0.3

--

 

V

 

 

 

 

 

 

 

 

Power Supply Current

IVCC

VSS = 0V

--

10

--

 

mA

Soft Start

 

 

 

 

 

 

 

Soft Start Current

ISS

 

8

10

15

 

μA

Oscillator

 

 

 

 

 

 

 

Free Running Frequency

fOSC

RT = 33kΩ

255

300

345

 

kHz

Frequency Variation

 

 

-15

--

15

 

%

Frequency Range

 

 

50

300

1000

 

kHz

Maximum Duty Cycle

 

 

70

75

80

 

%

 

 

 

 

 

To be continued

 

 

 

 

 

 

 

 

www.richtek.com

 

 

DS8805C-01

November

2005

4

 

Preliminary

 

RT8805C

 

 

 

 

 

 

 

Parameter

Symbol

Test Conditions

Min

Typ

Max

Units

Reference Voltage

 

 

 

 

 

 

Feedback Voltage

VFB

VFB = 0.8V

0.784

0.8

0.816

V

Error Amplifier

 

 

 

 

 

 

 

 

 

 

 

 

 

DC Gain

 

 

60

70

--

dB

 

 

 

 

 

 

 

Gain-Bandwidth Product

GBW

CLOAD = 5pF

6

10

--

MHz

Trans-conductance

GM

RLOAD = 20kΩ

600

660

--

μA/V

MAX Current (Source & Sink)

ICOMP

VCOMP = 2.5V

300

360

--

μ

 

 

 

 

A

Current Sense GM Amplifier

 

 

 

 

 

 

 

 

 

 

 

 

 

OC

VPHASE

RIMAX = 33kΩ

--

-220

--

mV

Gate Driver

 

 

 

 

 

 

Maximum Upper Drive Source

IUGATE(MAX)

BOOT − PHASE = 12V

1

--

--

A

Upper Drive Sink

RUGATE

VUGATE = 1V

--

3.5

7

Ω

Maximum Lower Drive Source

ILGATE(MAX)

PVCC = 12V

1

--

--

A

Lower Drive Sink

RLGATE

VLGATE = 1V

--

2

4

Ω

Protection

 

 

 

 

 

 

 

 

 

 

 

 

 

Under Voltage Protection

 

 

0.55

0.6

0.65

V

 

 

 

 

 

 

 

Power Sequence

 

 

 

 

 

 

 

 

 

 

 

 

 

Power Good Threshold

 

 

3.4

3.7

4

V

 

 

 

 

 

 

 

Power Good Sink Capability (4mA)

 

 

--

0.05

0.2

V

 

 

 

 

 

 

 

Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability.

Note 2. Devices are ESD sensitive. Handling precaution recommended.

Note 3. The device is not guaranteed to function outside its operating conditions.

Note 4. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard.

DS8805C-01 November 2005

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