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LTM4618

4618fa

TYPICAL APPLICATION

DESCRIPTION

6A DC/DC µModule

Regulator with Tracking and

Frequency Synchronization

The LTM

4618 is a complete 6A output switching mode

DC/DC power supply in a 9mm × 15mm × 4.32mm LGA

package. Included in the package are the switching con-

troller, power FETs, inductor and all support components.

Operating over an input voltage range of 4.5V to 26.5V,

the LTM4618 supports an output voltage range of 0.8V

to 5V set by a single external resistor. Its high efﬁ ciency

design delivers 6A continuous current (8A peak). Only a

few input and output capacitors are needed.

High switching frequency and a current mode architecture

enable a very fast transient response to line and load

changes without sacriﬁ cing stability. The device supports

frequency synchronization and output voltage tracking for

supply rail sequencing. Burst Mode operation or pulse-

skipping mode can be selected for light load operations.

Fault protection features include overvoltage protection,

overcurrent protection and foldback current limit for

short-circuit protection.

The LTM4618 is Pb-free and RoHS compliant.

L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and µModule are registered

trademarks and LTpowerCAD is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

2.5V/6A DC/DC Power μModule

with 6V to 26.5V Input

FEATURES

APPLICATIONS

Complete Standalone Power Supply

Wide Input Voltage Range: 4.5V to 26.5V

6A DC Typical, 8A Peak Output Current

0.8V to 5V Output

Output Voltage Tracking

±1.75% Maximum Total DC Error

Current Mode Control/Fast Transient Response

Phase-Lockable Fixed Frequency 250kHz to 780kHz

On-Board Frequency Synchronization

Selectable Burst Mode

Operation

Power Good Voltage Indicator

Output Overvoltage Protection

Output Current Foldback Limiting

9mm × 15mm × 4.32mm LGA Package

Telecom and Networking Equipment

Servers

Storage Cards

ATCA Cards

Industrial Equipment

Point of Load Regulation

Medical Systems

Efﬁ ciency and Power Loss vs Load Current

LOAD CURRENT (A)

EFFICIENCY (%)

POWER LOSS (W)

3.0

2.5

1.5

2.0

1.0

0.5

4618 TA01b

6315

POWER LOSS

EFFICIENCY

12V

TO 2.5V

OUT

24V

TO 2.5V

OUT

4618 TA01

COMP

TK/SS

RUN

FREQ

OUT

PGOOD

INTV

EXTV

MODE/PLLIN

LTM4618

SGND PGND

28.7k

OUT

2.5V/6A

0.1µF

6V to 26.5V

Summary of content (24 pages)

PAGE 1
LTM4618 6A DC/DC µModule Regulator with Tracking and Frequency Synchronization DESCRIPTION FEATURES n n n n n n n n n n n n n n Complete Standalone Power Supply Wide Input Voltage Range: 4.5V to 26.5V 6A DC Typical, 8A Peak Output Current 0.8V to 5V Output Output Voltage Tracking ±1.
PAGE 2
LTM4618 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VIN, SW ...................................................... –0.3V to 28V INTVCC, RUN, EXTVCC, PGOOD .................... –0.3V to 6V COMP, VFB ................................................. –0.3V to 2.7V MODE/PLLIN, TK/SS, FREQ ..................................................... –0.3V to INTVCC VOUT ............................................................... 0.8V to 5V Internal Operating Temperature Range (Note 2)....................
PAGE 3
LTM4618 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full internal operating temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2), VIN = 12V, per typical application in Figure 21. SYMBOL PARAMETER CONDITIONS IQ(VIN) Input Supply Bias Current VIN = 12V, VOUT = 2.5V, IOUT = 0A VIN = 26.5V, VOUT = 2.5V, IOUT = 0A Shutdown, RUN = 0, VIN = 26.5V MIN 26 20 80 IS(VIN) Input Supply Current VIN = 12V, VOUT = 2.5V, IOUT = 6A VIN = 26.5V, VOUT = 2.
PAGE 4
LTM4618 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full internal operating temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2), VIN = 12V, per typical application in Figure 21. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS fHIGH Highest Frequency VFREQ ≥ 2.4V, INTVCC 700 780 860 kHz VIH(MODE/PLLIN) Synchronous Clock High Level 2.
PAGE 5
LTM4618 TYPICAL PERFORMANCE CHARACTERISTICS Efﬁciency vs Load Current with 12VIN (CCM) 95 95 90 90 EFFICIENCY (%) 100 EFFICIENCY (%) 100 85 80 5V TO 0.8VOUT 5V TO 1.2VOUT 5V TO 1.5VOUT 5V TO 2.5VOUT 5V TO 3.3VOUT 75 70 0 1 95 90 85 80 12V TO 1.2VOUT 12V TO 1.5VOUT 12V TO 2.5VOUT 12V TO 3.
PAGE 6
LTM4618 TYPICAL PERFORMANCE CHARACTERISTICS Start-Up, IOUT = 0A Start-Up, IOUT = 6A VOUT 1V/DIV VOUT 1V/DIV IIN 0.2A/DIV IIN 0.5A/DIV 20ms/DIV VIN = 12V AND VOUT = 2.5V COUT = 2= 22μF 6.3V CERAMIC, 1= 100μF 6.3V CERAMIC AND 1= 220μF SANYO POSCAP CSOFT-START = 0.1μF 4618 G10 20ms/DIV VIN = 12V AND VOUT = 2.5V COUT = 2= 22μF 6.3V CERAMIC, 1= 100μF 6.3V CERAMIC AND 1= 220μF SANYO POSCAP CSOFT-START = 0.
PAGE 7
LTM4618 PIN FUNCTIONS NC (A1): No Connect. Leave ﬂoating. this pin turns on the module. Forcing this pin below 1.1V will shut down the output. The RUN pin has a 1μA pullup current source that increases to 10μA as the RUN pin voltage reaches 1.5V and up to compliance. Therefore the pin can be left ﬂoating for normal operation. A maximum of 6V can be applied to the pin. A voltage divider can be used for a UVLO function. See the Applications Information section. FREQ (A2): Frequency Selection Pin.
PAGE 8
LTM4618 PIN FUNCTIONS additional decoupling of the 5V internal regulator. VOUT (BANK 3: J1-J4, K1-K4, L1-L4, M1-M4): Power Output Pins. Apply output load between these pins and PGND pins. Recommend placing output decoupling capacitance directly between these pins and PGND pins. to check the switching frequency. Leave pin ﬂoating. A resistor-capacitor snubber can be placed from SW to PGND to eliminate high frequency switch node ringing. See the Applications Information section.
PAGE 9
LTM4618 OPERATION Power Module Description The LTM4618 is a standalone non-isolated switching mode DC/DC power supply. It can deliver up to 6A (DC current) output with few external input and output capacitors. This module provides precisely regulated output voltages programmable via external resistors from 0.8VDC to 5.0VDC over 4.5V to 26.5V input voltages. The typical application schematic is shown in Figure 21. For ≤6V inputs, connect VIN, INTVCC and EXTVCC together.
PAGE 10
LTM4618 APPLICATIONS INFORMATION The typical LTM4618 application circuit is shown in Figure 21. External component selection is primarily determined by the maximum load current and output voltage. VIN to VOUT Step-Down Ratios There are restrictions in the maximum VIN to VOUT stepdown ratio that can be achieved for a given input voltage. One of the restrictions is the minimum on-time tON(MIN), which is the smallest time duration that the LTM4618 can operate.
PAGE 11
LTM4618 APPLICATIONS INFORMATION The LTM4618 is designed for low output voltage ripple noise. The bulk output capacitors deﬁned as COUT are chosen with low enough effective series resistance (ESR) to meet the output voltage ripple and transient requirements. COUT can be a low ESR tantalum capacitor, a low ESR polymer capacitor or ceramic capacitor. The typical output capacitance range is from 100μF to 300μF.
PAGE 12
LTM4618 APPLICATIONS INFORMATION The LTM4618 can be synchronized from 400kHz to 780kHz with an input clock that has a high level above 2.0V and a low level below 0.8V. The 400kHz low end operation limit is put in place to limit inductor ripple current. See the Typical Applications section for synchronization examples. The LTM4618 minimum on-time is limited to about 90ns. Guardband the on-time to 110ns.
PAGE 13
LTM4618 APPLICATIONS INFORMATION Slope Compensation The module has already been internally compensated for all output voltages. LTpowerCAD is available for further control loop optimization. RUN Pin The RUN pin has a 1μA pull-up current source that will enable the device in a ﬂoat condition. A voltage divider can be used to enable a UVLO function using the RUN pin. See Figure 21.
PAGE 14
LTM4618 APPLICATIONS INFORMATION board, and is really the sum of the θJCbottom and the thermal resistance of the bottom of the part through the solder joints and through a portion of the board. The board temperature is measured at speciﬁed distance from the package, using a two sided, two layer board. This board is described in JESD 51-9.
PAGE 15
LTM4618 APPLICATIONS INFORMATION The 1.5V and 3.3V power loss curves in Figures 7 and 8 can be used in coordination with the load current derating curves in Figures 9 to 16 for calculating an approximate θJA thermal resistance for the LTM4618 with various heat sinking and air ﬂow conditions. The power loss curves are taken at room temperature, and are increased with multiplicative factors according to the ambient temperature. These approximate factors are: 1 for 40°C; 1.05 for 50°C; 1.1 for 60°C; 1.
PAGE 16
LTM4618 6 6 5 5 5 4 3 2 1 0 0LFM 200LFM 400LFM 70 75 LOAD CURRENT (A) 6 LOAD CURRENT (A) LOAD CURRENT (A) APPLICATIONS INFORMATION 4 3 2 1 0 80 85 90 95 100 105 110 115 AMBIENT TEMPERATURE (°C) 75 2 0 80 85 90 95 100 105 110 115 AMBIENT TEMPERATURE (°C) 4618 F09 Figure 10. 5VIN to 1.
PAGE 17
LTM4618 APPLICATIONS INFORMATION Table 2. 1.5V Output DERATING CURVE VIN (V) POWER LOSS CURVE AIRFLOW (LFM) HEAT SINK ΘJA (°C/W) Figures 9, 11 5, 12 Figure 7 0 None 16 Figures 9, 11 5, 12 Figure 7 200 None 12.2 Figures 9, 11 5, 12 Figure 7 400 None 11.2 Figures 10, 12 5, 12 Figure 7 0 BGA Heat Sink 15.2 Figures 10, 12 5, 12 Figure 7 200 BGA Heat Sink 11.6 Figures 10, 12 5, 12 Figure 7 400 BGA Heat Sink 10.
PAGE 18
LTM4618 APPLICATIONS INFORMATION VISHAY INLP1616BZERR22M01 0.22μH π FILTER VIN 6V TO 26.5V 10μF s2 CIN 10μF s2 VIN C1 0.1μF R1 ¥ R2 ´ r 1.22V VIN • ¦ § R1 R2 µ¶ INTVCC VIN MODE/PLLIN EXTVCC FREQ VOUT COMP LTM4618 VFB TK/SS RUN SGND PGND PGOOD C2 47pF VOUT COUT 3.3V/6A 100μF s3 19.1k SW 4618 F17 RSNUB 1.2Ω 0805 R2 CSNUB 470pF 0805, 50V Figure 17. 6V to 26.5V Input, 3.
PAGE 19
LTM4618 APPLICATIONS INFORMATION EMI Section The LTM4618 has been evaluated for CISPR22 A and B Radiated EMI and CISPR25 Conducted EMI. The CISPR25 Conducted EMI test was performed with an input π ﬁlter as shown in Figure 17. An RC snubber circuit is optionally used from the SW pin to the PGND pin to improve the higher frequency attenuation and EMI limit guard band. Figure 18 shows the CISPR25 conducted emissions plot for 26.5V input to 3.3V output at 5A load.
PAGE 20
LTM4618 TYPICAL APPLICATIONS 31.6k VIN 6V TO 26.5V VIN ¥ R2 ´ VIN • ¦ r 1.22V § R1 R2 µ¶ UVLO FUNCTION CIN 10μF s2 C1 0.1μF INTVCC VIN MODE/PLLIN EXTVCC FREQ 10k VOUT COMP VFB TK/SS 28.7k PGOOD RUN R1 SGND VOUT COUT 2.5V/6A 100μF s3 C2 47pF LTM4618 PGND 4618 F21 R2 Figure 21. Typical 6V to 26.5V Input, 2.5V at 6A Design, 500kHz Operation CLOCK SYNC 0° PHASE PGOOD VIN VIN 6V TO 26.5V CIN1 10μF MODE/PLLIN FREQ VOUT COMP LTM4618 VFB TK/SS C3 ON/OFF 0.47μF RUN SGND R5 165k C5 0.
PAGE 21
ISOLATED INTERMEDIATE BUS R1 19.1k TK/SS COMP CIN2 10μF RUN TK/SS COMP C7 100μF 35V OPT VFB VOUT FREQ R2 19.1k C2 22pF R1 11.5k C1 47pF COUT2 100μF s2 R9 28.7k R8 60.4k R11 48.7k R10 60.4k VOUT1 VOUT2 3.3V/6A COUT1 100μF VOUT1 5V/6A VOUT1 4-PHASE OSCILLATOR SET V+ U5 MOD DIV LTC6902 GND PH OUT4 OUT1 OUT3 OUT2 CIN4 10μF ON/OFF CIN3 10μF C8 0.
PAGE 22
LTM4618 PACKAGE PHOTOGRAPH PACKAGE DESCRIPTION Pin Assignment Tables (Arranged by Pin Function) PIN NAME PIN NAME PIN NAME PIN NAME A1 A2 A3 A4 A5 A6 A7 N/C FREQ MODE/PLLIN PGND VIN VIN VIN D1 D2 D3 D4 D5 D6 D7 VFB PGOOD INTVCC PGND PGND PGND PGND G1 G2 G3 G4 G5 G6 G7 PGND PGND PGND PGND PGND PGND PGND K1 K2 K3 K4 K5 K6 K7 VOUT VOUT VOUT VOUT PGND SW PGND B1 B2 B3 B4 B5 B6 B7 TK/SS RUN SGND PGND VIN VIN VIN E1 E2 E3 E4 E5 E6 E7 PGND PGND PGND PGND PGND PGND PGND H1 H2 H3 H4 H5 H6 H7 PGND P
PAGE 23
4 9.00 BSC PACKAGE TOP VIEW Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 2.540 2.540 SUGGESTED PCB LAYOUT TOP VIEW 1.270 0.315 0.315 0.000 PAD “A1” CORNER 1.270 Y X 6.985 5.715 4.445 3.175 1.905 0.635 0.000 0.635 1.905 3.175 4.
PAGE 24
LTM4618 TYPICAL APPLICATION 5V Input, 2.5V at 6A Design, 500kHz Operation 31.6k VIN 5V 4.5V ≤ VIN ≤ 6V VIN CIN 10μF s2 C1 0.1μF R1 ¥ R2 ´ VIN • ¦ r 1.22V § R1 R2 µ¶ INTVCC VIN MODE/PLLIN EXTVCC FREQ VOUT COMP LTM4618 VFB TK/SS PGOOD RUN SGND 10k C2 47pF VOUT COUT 2.5V/6A 100μF s3 28.7k PGND 4618 TA02 UVLO FUNCTION R2 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTM4603 6A DC/DC μModule Regulator with PLL and Output Tracking/Margining 4.5V to 20V Input, 0.