Richtek RT8248AGQW Schematic [ru]

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RT8248A

Complete DDR Memory Power Supply Controller

General Description

The RT8248Aprovides a complete power supply forDDR2/ DDR3/DDR3L/LPDDR3/DDR4 memory systems. It integrates a synchronous PWM Buck controller with a 1.5A sink/source tracking linear regulator and buffered low noise reference.

The PWM controller provides the low quiescent current, high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high-voltage batteries to generate low-voltage chipset RAM supplies in notebook computers. The constant on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency.

The RT8248A achieves high efficiency at a reduced cost by eliminating the current-sense resistor found in traditional current mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronous rectifier MOSFETs. The Buck conversion allows this device to directly step down high-voltage batteries for the highest possible efficiency.

The 1.5A sink/source LDO maintains fast transient response only requiring a 10μF ceramic output capacitor. In addition, the LDO supply input is available externally to significantly reduce the total power losses. The IC supports all of the sleep state controls placing VTT at high-Z in S3 and discharging VDDQ, VTT and VTTREF (soft-off) in S4/S5.

The RT8248A provides protections including OVP, UVP, and thermal shutdown and available in the WQFN-20L 3x3 package.

Features

PWM Controller

Adjustable Current Limit with Low-Side RDS(ON) Sensing

Low Quiescent Supply Current

Quick Load-Step Response within 100ns

1% VVDDQ Accuracy Over Line and Load

Adjustable 0.675V to 3.3V Output Range for 1.8V

(DDR2), 1.5V (DDR3), 1.35V (DDR3L), 1.2V (LPDDR3) and 1.2V (DDR4)

4.5V to 26V Battery Input Range

Resistor Adjustable Frequency

Over-/Under-Voltage Protection

Internal Voltage Ramp Soft-Start

Drives Large Synchronous Rectifier MOSFETs

Power Good Indicator

1.5A LDO (VTT), Buffered Reference (VTTREF)

Capable to Sink and Source Up to 1.5A

LDO Input Available to Optimize Power Losses

Requires Only 10μF Ceramic Output Capacitor

Integrated Divider Tracks 1/2 VDDQ for both VTT and VTTREF

Accuracy ±20mV for both VTTREF and VTT

Supports High-Z in S3 and Soft-Off in S4/S5

Simplified Application Circuit

VIN

VVDD

VDD

RT8248A

TON

 

 

 

UGATE

 

 

 

 

 

 

PGOOD

PGOOD

 

BOOT

 

 

 

 

VTT

VTT

 

 

PHASE

V

 

 

LGATE

 

 

VTTSNS

 

 

 

 

 

 

 

CS

 

 

FB

 

 

S3

 

VTTREF

 

 

 

 

VDDQ

 

 

S5

 

 

 

 

 

 

 

 

 

VID

 

GND VLDOIN

 

VDDQ

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8248A-04 October 2014

www.richtek.com

 

1

RT8248A

 

 

 

 

 

 

 

 

Applications

 

 

 

 

 

 

Ordering Information

DDR2/DDR3/DDR3L/LPDDR3/DDR4 Memory Power

RT8248A

Package Type

Supplies

 

 

 

 

 

 

 

Notebook computers

 

 

 

 

 

 

QW : WQFN-20L 3x3 (W-Type)

 

 

 

 

 

 

Lead Plating System

SSTL18, SSTL15 and HSTL bus termination

 

 

G : Green (Halogen Free and Pb Free)

Pin Configurations

 

 

Note :

 

 

 

 

(TOP VIEW)

 

Richtek products are :

 

VTT

VLDOIN

BOOT

UGATE

PHASE

 

RoHS compliant and compatible with the current require-

 

 

ments of IPC/JEDEC J-STD-020.

 

 

 

 

 

 

 

 

20 19 18 17 16

 

Suitable for use in SnPb or Pb-free soldering processes.

VTTGND

1

 

 

 

15

LGATE

Marking Information

VTTSNS

2

GND

14

PGND

GND

3

13

CS

RT8248AGQW

 

VTTREF

4

 

 

21

12

VDD

 

VDDQ

5

 

 

 

11

VID

 

5E= : Product Code

 

6

7

8

9

10

 

5E=YM

YMDNN : Date Code

 

FB S3 S5

TON

PGOOD

 

 

 

DNN

 

 

 

 

 

 

 

 

 

 

WQFN-20L 3x3

 

 

 

Functional Pin Description

Pin No.

Pin Name

 

Pin Function

1

VTTGND

Power Ground for the VTT LDO.

2

VTTSNS

Voltage Sense Input for the VTT LDO. Connect to the terminal of the VTT_LDO

output capacitor.

 

 

 

 

3, 21

GND

The exposed pad must be soldered to a large PCB and connected to GND for

(Exposed Pad)

maximum power dissipation.

4

VTTREF

VTTREF Buffered Reference Output.

5

VDDQ

Reference Input for VTT and VTTREF.

6

FB

Feedback Voltage Input. Connect to a resistive voltage divider from VDDQ to

GND to adjust the output voltage.

 

 

7

S3

VTT LDO Enable Control Input. Do not leave this pin floating.

8

S5

PWM Enable Control Input. Do not leave this pin floating.

9

TON

Set the UGATE On-Time Through a Pull-Up Resistor Connecting to VIN.

10

PGOOD

Power Good Open-Drain Output. In high state when VDDQ output voltage is

within the target range.

 

 

 

 

11

VID

Internal Reference Voltage Setting.

12

VDD

Supply Voltage Input for the Analog Supply and LGATE Gate Driver.

13

CS

Current Limit Threshold

Setting Input. Connect to GND through the voltage

setting resistor.

 

 

 

 

14

PGND

Power Ground for Low-Side MOSFET.

15

LGATE

Low-Side Gate Driver Output for VDDQ.

16

PHASE

Switch Node. External inductor connection for VDDQ and behave as the current

sense comparator input for Low-Side MOSFET RDS(ON) sensing.

 

 

17

UGATE

High-Side Gate Driver Output for VDDQ.

18

BOOT

Bootstrap Supply for High-Side Gate Driver.

19

VLDOIN

Power Supply for VTT LDO.

20

VTT

Power Output for the VTT LDO.

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8248A-04 October 2014

2

 

Richtek RT8248AGQW Schematic

RT8248A

Function Block Diagram

Buck Controller

TRIG

VDDQ

 

On-Time

 

 

 

 

 

BOOT

TON

 

1-SHOT

 

 

R

 

 

 

 

 

+ Comp

 

 

 

 

 

 

 

 

 

 

 

 

 

VREF

 

 

 

 

 

 

 

 

+

S

Q

 

UGATE

 

 

 

 

-

 

 

 

 

 

 

 

 

 

 

 

PHASE

 

 

+

OV

Latch

Min. TOFF

 

 

VDD

 

 

S1

Q

 

 

 

115%VREF

-

 

TRIG

 

 

 

 

 

 

 

 

 

 

FB

 

+

UV

Latch

 

 

 

LGATE

0.45V

S1

Q

 

 

 

 

-

 

 

 

 

PGND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-

DEM

 

 

 

 

 

 

85% VREF

+

 

 

 

 

SS Int

SS Timer

Thermal

 

+

 

5µA

 

 

 

 

 

Shutdown

 

-

1/10

CS

 

 

 

 

 

S5

 

 

 

Reference

 

 

 

 

 

 

 

 

Voltage

VREF

 

 

 

 

 

 

 

Selector

 

 

 

 

 

 

 

VDD

 

VID

PGOOD

 

 

 

VTT LDO

 

 

 

 

 

 

 

 

 

 

 

 

 

VDDQ

 

 

 

 

S5

Non-Tracking

 

 

Thermal

 

 

VTTREF

 

 

 

 

 

S3

Discharge

 

 

Shutdown

 

 

VLDOIN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

-

 

 

 

GND

 

 

 

 

 

+

 

 

VTT

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

+

 

 

VTTSNS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VTTGND

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8248A-04 October 2014

www.richtek.com

 

3

RT8248A

Operation

The RT8248A is a constant on-time synchronous stepdown controller. In normal operation, the high-side N-MOSFET is turned on when the output voltage is lower than VREF, and is turned off after the internal one-shot timer expires. While the high-side N-MOSFET is turned off, the low-side N-MOSFET is turned on to conduct the inductor current until next cycle begins.

Soft-Start (SS)

For internal soft-start function, an internal current source charges an internal capacitor to build the soft-start ramp voltage. The output voltage will track the internal ramp voltage during soft-start interval.

PGOOD

The power good output is an open-drain architecture. When the soft-start is finished, the PGOOD open-drain output will be high impedance.

Current Limit

The current limit circuit employs a unique “valley” current sensing algorithm. If the magnitude of the current sense signal at PHASE is above the current limit threshold, the PWM is not allowed to initiate a new cycle. The current limit threshold can be set with an external voltage setting resistor on the CS pin.

Over-Voltage Protection (OVP) & Under-Voltage Protection (UVP)

The output voltage is continuously monitored for overvoltage and under-voltage protection. When the output voltage exceeds its set voltage threshold( 115% of VOUT), UGATE goes low and LGATE is forced high. When the feedback voltage is less than 0.45V, under-voltage protection is triggered and then both UGATE and LGATE gate drivers are forced low. The controller is latched until VDD is re-supplied and exceeds the POR rising threshold voltage or S5 is reset.

VTT Linear Regulator and VTTREF

This VTT linear regulator employs ultimate fast response feedback loop so that small ceramic capacitors are enough for keeping track of VTTREF within 40mV at all conditions, including fast load transient. The VTTREF block consists of on-chip 1/2 divider, LPF and buffer. This regulator also has sink and source capability up to 10mA. Bypass VTTREF to GND with a 33nF ceramic capacitor for stable operation.

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8248A-04 October 2014

4

 

 

RT8248A

Absolute Maximum Ratings (Note 1)

 

Supply Input Voltage, TON to GND ------------------------------------------------------------------------------------

−0.3V to 32V

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

−0.3V to 6V

PHASE to GND

 

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

−0.3V to 32V

< 20ns -----------------------------------------------------------------------------------------------------------------------

−8V to 38V

LGATE to GND

 

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

−0.3V to 6V

< 20ns -----------------------------------------------------------------------------------------------------------------------

−2.5V to 7.5V

UGATE to PHASE

 

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

−0.3V to 6V

< 20ns -----------------------------------------------------------------------------------------------------------------------

−5V to 7.5V

VDD, CS, S3, S5, VTTSNS, VDDQ, VID, VTTREF, VTT, VLDOIN, FB, PGOOD to GND ----------------

−0.3V to 6V

PGND, VTTGND to GND -------------------------------------------------------------------------------------------------

−0.3V to 0.3V

Other Pins-------------------------------------------------------------------------------------------------------------------

−0.3V to 6.5V

Power Dissipation, PD @ TA = 25°C

 

WQFN-20L 3x3 ------------------------------------------------------------------------------------------------------------

3.33W

Package Thermal Resistance (Note 2)

 

WQFN-20L 3x3, θJA -------------------------------------------------------------------------------------------------------

30°C/W

WQFN-20L 3x3, θJC ------------------------------------------------------------------------------------------------------

7.5°C/W

Junction Temperature -----------------------------------------------------------------------------------------------------

150°C

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

260°C

Storage Temperature Range --------------------------------------------------------------------------------------------

−65°C to 150°C

ESD Susceptibility (Note 3)

 

HBM (Human Body Model) ----------------------------------------------------------------------------------------------

2kV

Recommended Operating Conditions (Note 4)

 

Input Voltage, VIN ---------------------------------------------------------------------------------------------------------

4.5V to 26V

Control Voltage, VDD -----------------------------------------------------------------------------------------------------

4.5V to 5.5V

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

−40°C to 125°C

Ambient Temperature Range --------------------------------------------------------------------------------------------

−40°C to 85°C

Electrical Characteristics

(VDD = 5V, VIN = 12V, RTON = 620kΩ, TA = 25°C, unless otherwise specified)

Parameter

Symbol

 

Test Conditions

Min

Typ

Max

 

Unit

 

 

 

 

 

 

 

 

 

 

PWM Controller

 

 

 

 

 

 

 

 

 

Quiescent Supply Current

 

FB Forced above the Regulation Point,

--

135

--

 

A

 

VS5

= 5V, VS3

= 0V, Not Switching

 

 

 

 

 

 

 

 

TON Operating Current

 

RTON = 620k , VIN = 12V

--

19

--

 

A

IVLDOIN BIAS Current

 

VS5

= VS3 = 5V, VTT = No Load

--

1

--

 

A

IVLDOIN Standby Current

 

VS5

= 5V, VS3

= 0, VTT = No Load

--

0.1

10

 

A

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

 

DS8248A-04 October 2014

www.richtek.com

 

5

RT8248A

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

 

 

VDD

--

0.1

10

A

 

 

 

 

 

 

 

Shutdown Current

 

TON

--

0.1

5

A

 

 

 

 

 

 

ISHDN

S5/S3

1

0.1

1

A

(VS5 = VS3 = 0V)

 

 

 

 

 

 

 

VLDOIN

--

0.1

1

A

 

 

 

 

 

 

 

 

 

 

 

VID

--

0.5

1

A

 

 

 

 

 

 

 

FB Error Comparator

VREF

VREF = 0.675V/0.75V

1

0

1

%

Threshold

 

 

 

 

 

 

VDDQ Voltage Range

 

 

0.675

--

3.3

V

 

 

 

 

 

 

 

Switch Frequency

fSW

RTON = 620k, VIN = 12V,

320

400

480

kHz

VDDQ = 1.5V, IOUT = 20A (Note 5)

 

 

 

 

 

 

Minimum Off-Time

 

 

250

400

550

ns

 

 

 

 

 

 

 

VDDQ Shutdown Discharge

 

VS5 = 0V, VS3 = 0V

--

15

--

 

Resistance

 

 

 

 

 

 

 

Current Sensing

 

 

 

 

 

 

CS Pin Source Current

 

 

4.5

5

5.5

A

 

 

 

 

 

 

 

Zero Crossing Threshold

 

GND PHASE

5

--

10

mV

 

 

 

 

 

 

 

Fault Protection

 

 

 

 

 

 

 

 

 

 

 

 

 

Current Limit (Positive)

 

GND PHASE, RCS = 160k

70

80

90

mV

Output UV Threshold

VUVP

VFB Falling. For both VID is high or

0.4

0.45

0.5

V

low.

 

 

 

 

 

 

UVP Latch Delay

 

FB Forced below UV Threshold

--

30

--

s

 

 

 

 

 

 

 

OVP Threshold

VOVP

With Respect to Error Comparator

110

115

120

%

Threshold

 

 

 

 

 

 

OVP Latch Delay

 

FB Forced above OV Threshold

--

5

--

s

 

 

 

 

 

 

 

VDD POR Threshold

 

Rising Edge, Hysteresis = 120mV,

3.9

4.2

4.5

V

 

PWM Disabled below this Level

 

 

 

 

 

 

Voltage Ramp Soft-Start Time

 

From S5 Going High to VFB = 0.675V

--

1

--

mS

UV Blank Time

 

From S5 Signal Going High

--

5

--

mS

 

 

 

 

 

 

 

Thermal Shutdown

TSD

 

--

165

--

C

Driver On-Resistance

 

 

 

 

 

 

UGATE Gate Driver Source

RUGATEsr

BOOT PHASE Forced to 5V

--

2.5

5

 

UGATE Gate Driver Sink

RUGATEsk

BOOT PHASE Forced to 5V

--

1.5

3

 

LGATE Gate Driver Source

RLGATEsr

DL, High State

--

2.5

5

 

 

 

 

 

 

 

 

LGATE Gate Driver Sink

RLGATEsk

DL, Low State

--

0.8

1.6

 

Dead Time

 

LGATE Rising (Phase = 1.5V)

--

40

--

ns

 

 

 

 

 

 

UGATE Rising

--

40

--

 

 

 

 

 

 

 

 

 

 

Internal Boost Charging Switch

 

VDD to BOOT, 10mA

--

--

80

 

On-Resistance

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8248A-04 October 2014

6

 

RT8248A

Parameter

Symbol

Test Conditions

 

 

 

Min

Typ

Max

Unit

Logic I/O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S3, S5 Input

 

Logic-High

 

 

 

 

 

 

 

 

2

--

--

V

Voltage

 

Logic-Low

 

 

 

 

 

 

 

 

--

--

0.8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Logic Input Current

 

 

S3, S5 = VDD / GND

 

 

 

 

 

1

0

1

A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VID Input

 

Logic-High

 

 

 

 

 

 

 

 

750

--

--

mV

Threshold Voltage

 

Logic-Low

 

 

 

 

 

 

 

 

--

--

300

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PGOOD (Upper Side Threshold Decide by OV Threshold)

 

 

 

 

 

 

 

 

 

Trip Threshold (Falling)

 

Measured at FB, with Respect to

 

20

15

10

%

 

Reference, No Load. Hysteresis = 2%

Fault Propagation Delay

 

Falling Edge, FB Forced below

 

--

5

--

s

 

PGOOD Trip Threshold

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Output Low Voltage

 

 

ISINK = 1mA

 

 

 

 

 

--

--

0.4

V

Leakage Current

 

ILEAK

High State, Forced to 5V

 

 

 

--

--

1

A

VTT LDO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VDDQ = VLDOIN = 1.2V/1.35V/1.5V/

 

20

--

20

 

 

 

 

 

1.8V, |IVTT| = 0A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VDDQ = VLDOIN = 1.2V/1.35V/1.5V/

 

30

--

30

 

 

 

 

 

1.8V, |IVTT| < 1A

 

 

 

 

 

 

VTT Output Tolerance

VVTTTOL

 

 

 

 

 

 

 

 

mV

VDDQ = VLDOIN = 1.2V/1.35V,

 

40

--

40

 

 

 

 

 

 

 

 

 

 

|IVTT| < 1.2A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VDDQ = VLDOIN = 1.5V/1.8V,

 

 

 

40

--

40

 

 

 

 

 

|IVTT| < 1.5A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VTT Source Current Limit

IVTTOCLSRC

VTT = 0V

 

 

 

 

 

1.6

2.6

3.6

A

VTT Sink Current Limit

IVTTOCLSNK

VTT = VDDQ

 

 

 

 

 

1.6

2.6

3.6

A

 

 

 

 

 

 

 

VVDDQ

10

 

 

A

VTT Leakage Current

IVTTLK

S5 = 5V, S3 = 0V, VTT =

 

 

 

 

--

10

 

2

 

 

 

 

 

 

 

 

 

 

 

 

VTTSNS Leakage Current

IVTTSNSLK

ISINK = 1mA

 

 

 

 

 

1

--

1

A

VTT Discharge Current

IDSCHRG

VDDQ = 0V, VTT = 0.5V, S5 = S3 = 0V

10

30

--

mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VVDDQ

 

 

 

 

 

 

 

 

 

VVTT = VVTTREF =

 

 

 

 

,

 

--

0.75

--

V

VTTREF Output Voltage

VVTTREF

 

2

 

 

 

 

 

 

 

 

 

 

 

 

VVDDQ = 1.5V

 

 

 

 

 

 

 

 

 

 

 

 

 

VLDOIN = VVDDQ = 1.5V,

 

 

 

 

 

15

--

15

 

VDDQ/2, VTTREF Output

 

|IVTTREF| < 10mA

 

 

 

 

 

 

VVTTREFTOL

 

 

 

 

 

 

 

 

mV

Voltage Tolerance

 

VLDOIN = VVDDQ = 1.8V,

 

 

 

 

 

18

--

18

 

 

 

 

 

 

 

 

 

 

 

 

 

 

|IVTTREF| < 10mA

 

 

 

 

 

 

 

 

 

VTTREF Source Current Limit

IVTTREFOCL

VVTTREF = 0V

 

 

 

 

 

10

40

80

mA

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8248A-04 October 2014

www.richtek.com

 

7

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