PDF《PM8908》

This is information on a product in full production.

July

2017 DocID027688 Rev

4 1/28 PM8908 Monolithic buck converter for DDR memory termination Datasheet - production data Features ? Integrated MOSFETs for high efficiency ? Current COT architecture ?

1 V to 3.5 V input voltage (VIN) ? 5.0 V supply voltage (VCC) ? Constant frequency mode ? 1% output voltage accuracy ? Two programmable switching frequencies (0.6 MHz or

1 MHz) ? ADJ output voltage from 0.5 V to

2 V ? Embedded bootstrap diode ? OV/UV/OC and overtemperature protection ? Soft-off with integrated discharge resistor ? External tracking ? Power Good output ? QFN20 3.5 x 4.0 mm compact package Applications ? Memory termination regulator for DDR3, DDR4 and low power DDR3/DDR4 ? Notebook/desktop/server ? Low voltage application for

1 V to 3.5 V input rails Description The PM8908 is a high efficiency monolithic step- down switching regulator designed mainly for the DDR termination. The IC operates from

1 V to 3.5 V input voltage (VIN). The device uses a COT control loop that provides very good performances in terms of load and line transients. The current sense is internally thermally compensated for optimum precision. The output voltage is adjusted from 0.5 V to

2 V with ± 1% accuracy overtemperature variations. The PM8908 also provides external tracking support. The PM8908 provides positive and negative overcurrent protection as well as over/undervoltage and overtemperature protection. PGOOD output easily provides real- time information on the output voltage. The PM8908 is available in a QFN20 3.5 x 4.0 mm package. QFN20 3.5 x 4.0 mm Table 1. Device summary Order code Package Packaging PM8908TR QFN20 (3.5 x 4.0 mm) Tape and reel www.st.com Contents PM8908 2/28 DocID027688 Rev

4 Contents

1 Typical application circuit and block diagram

4 1.1 Application circuit

4 1.2 Block diagram

5 2 Pin description and connection diagrams

6 Pin description

6 3 Thermal data

8 4 Electrical specifications

9 4.1 Absolute maximum ratings

9 4.2 Electrical characteristics

10 5 Device description

13 5.1 Power section

13 5.2 Device configuration

14 5.3 Startup and shutdown management

14 Soft-off

16 5.4 Output voltage monitoring and protection

16 5.4.1 Overvoltage protection

16 5.4.2 Undervoltage protection

17 5.4.3 Power Good (PGOOD)17 5.4.4 Overcurrent protection

17 5.4.5 Overtemperature protection

18 6 Application information

19 6.1 Output voltage setting

19 6.2 Droop setting

19 6.3 Non-droop setting

20 6.4 Inductor design

20 6.5 Output capacitors

21 6.6 Input capacitors

21 6.7 Compensation network

22 DocID027688 Rev

4 3/28 PM8908 Contents

28 7 Package information

23 7.1 QFN20 package information

24 8 Revision history

27 Typical application circuit and block diagram PM8908 4/28 DocID027688 Rev

4 1 Typical application circuit and block diagram 1.1 Application circuit Figure 1. Typical application circuit Figure 2. Typical memory termination application circuit L RPGOOD PM8908 PGOOD EN MODE VOUT COMP REFIN PGND PHASE BOOT VIN VCC GND VIN =

1 V to 3.5 V VCC =

5 V CBOOT CF COUT CVIN CVCC

20 4,

5 1, 2,

3 11, 12, 13, 14,

15 16

10 8

9 6

19 17

18 R1 RF RM REF

7 R2 CREF VOUT CP L RPGOOD PM8908 PGOOD EN MODE VOUT COMP REFIN PGND PHASE BOOT VIN VCC GND VDDQ = 1.2 V VCC =

5 V CBOOT CF COUT CVIN CVCC

20 4,

5 1, 2,

3 11, 12, 13, 14,

15 16

10 8

9 6

19 17

18 R1 RF RM REF

7 R2 CREF VOUT = 0.6 V VDDQ R1=R2 CP DocID027688 Rev