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LTC3602

3602fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

2.5A, 10V, Monolithic

Synchronous Step-Down

Regulator

The LTC

3602 is a high efﬁ ciency, monolithic synchronous,

step-down DC/DC converter utilizing a constant-frequency,

current mode architecture. It operates from an input voltage

range of 4.5V to 10V and provides an adjustable regulated

output voltage from 0.6V to 9.5V while delivering up to

2.5A of output current. The internal synchronous power

switch with 65mΩ on-resistance increases efﬁ ciency

and eliminates the need for an external Schottky diode.

The switching frequency can either be set by an external

resistor or synchronized to an external clock. OPTI-LOOP

compensation allows the transient response to be optimized

over a wide range of loads and output capacitors.

The LTC3602 can be conﬁ gured for either Burst Mode op-

eration or forced continuous operation. Forced continuous

operation reduces noise and RF interference, while Burst

Mode operation provides the high efﬁ ciency at light loads.

In Burst Mode operation, external control of the burst

clamp level allows the output voltage ripple to be adjusted

according to the requirements of the application.

3.3V, 2.5A, 1MHz Step-Down Regulator

Wide Input Voltage Range: 4.5V to 10V

2.5A Output Current

Low R

DS(ON)

Internal Switches: 65mΩ and 90mΩ

Programmable Frequency: 300kHz to 3MHz

Low Quiescent Current: 75μA

0.6V ±1% Reference Allows Low Output Voltage

99% Maximum Duty Cycle

Adjustable Burst Mode

Clamp

Synchronizable to External Clock

Power Good Output Voltage Monitor

Overtemperature Protection

Available in 16-Lead Exposed TSSOP and

4mm × 4mm QFN Packages

Point-of-Load Supplies

Portable Instruments

Server Backplane Power

Battery-Powered Devices

Efﬁ ciency and Power Loss vs Load Current

105k

3602 TA01

22μF

100μF

0.22μF

2.2μH

1μF

1nF

RUN

PGOOD

TRACK/SS

BOOST

PGND

LTC3602

INTV

SYNC/MODE V

105k

475k

22pF

4.32k

OUT

3.3V

2.5A

4.5V TO 10V

, LT, LTC, LTM, Burst Mode and OPTI-LOOP are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

LOAD CURRENT (A)

0.01

EFFICIENCY (%)

POWER LOSS (mW)

100

0.1 1 10

3602 TA01b

100

1000

10000

POWER LOSS

EFFICIENCY

= 7V

Summary of content (20 pages)

PAGE 1
LTC3602 2.5A, 10V, Monolithic Synchronous Step-Down Regulator DESCRIPTION FEATURES n n n n n n n n n n n n Wide Input Voltage Range: 4.5V to 10V 2.5A Output Current Low RDS(ON) Internal Switches: 65mΩ and 90mΩ Programmable Frequency: 300kHz to 3MHz Low Quiescent Current: 75μA 0.
PAGE 2
LTC3602 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (PVIN) ....................... –0.3V to 11V SW (DC)...................................... –0.3V to (PVIN + 0.3V) BOOST ................................. (VSW –0.3V) to (VSW + 6V) RUN ........................................................... –0.3V to 11V All Other Pins ............................................... –0.3V to 6V Peak SW Sink and Source Current (Note 7) .............6.5A Operating Temperature Range (Note 2)....
PAGE 3
LTC3602 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 8.4V unless otherwise speciﬁed. SYMBOL PARAMETER TYP MAX UNITS ΔVPGOOD Power Good Range CONDITIONS MIN ±10 ±12 % RPGOOD Power Good Resistance 11 18 Ω IFB FB Input Bias Current 10 nA gm Transconductance Ampliﬁer gm 1.
PAGE 4
LTC3602 TYPICAL PERFORMANCE CHARACTERISTICS Switch On-Resistance vs Input Voltage VREF vs Temperature 95 RESISTANCE (mΩ) 0.6004 VREF (V) TOP 90 0.6006 0.6002 0.6000 0.5998 140 VBOOST – VSW = INTVCC VIN = 8.
PAGE 5
LTC3602 TYPICAL PERFORMANCE CHARACTERISTICS Minimum Peak Inductor Current vs Burst Clamp Voltage Maximum Peak Inductor Current vs Duty Cycle 100 5 2.0 1.5 1.0 0.5 0 0.4 0.7 0.9 0.5 0.6 0.8 BURST CLAMP VOLTAGE (V) 3 2 1 0 1.0 Efﬁciency vs Input Voltage 95 ILOAD = 1A 90 ILOAD = 2.5A 96 50 VIN = 9V EFFICIENCY (%) 60 85 80 2.2μH 94 92 1μH 90 88 20 75 84 70 0.1 1 LOAD CURRENT (A) 4 10 4.7μH 86 10 0 0.
PAGE 6
LTC3602 PIN FUNCTIONS FE/UF Package SYNC/MODE (Pin 1/Pin 4): Mode Select and External Clock Synchronization Input. be programmed by connecting a capacitor between this pin and ground. Leave this pin ﬂoating to use the internal 1ms soft-start clamp. Do not tie this pin to INTVCC or to PVIN. PGOOD (Pin 2/Pin 5): Power Good Output. Open-drain logic output that is pulled to ground when the output voltage is not within ±10% of regulation point. PGND (Pins 8, 9, 10/Pins 12, 13, 14, 15): Power Ground.
PAGE 7
LTC3602 OPERATION Main Control Loop Burst Mode Operation The LTC3602 is a monolithic, constant-frequency, currentmode step-down DC/DC converter. During normal operation, the internal top power switch (N-channel MOSFET) is turned on at the beginning of each clock cycle. Current in the inductor increases until the current comparator trips and turns off the top power MOSFET. The peak inductor current at which the current comparator shuts off the top power switch is controlled by the voltage on the ITH pin.
PAGE 8
LTC3602 OPERATION Dropout Operation Overtemperature Protection When the input supply voltage decreases toward the output voltage, the duty cycle increases toward the maximum on-time. Further reduction of the supply voltage forces the top switch to remain on for more than one cycle until it attempts to stay on continuously.
PAGE 9
LTC3602 APPLICATIONS INFORMATION The basic LTC3602 application circuit is shown on the front page of this data sheet. External component selection is determined by the maximum load current and begins with the selection of the inductor value and operating frequency followed by CIN and COUT. Operating Frequency Selection of the operating frequency is a tradeoff between efﬁciency and component size. High frequency operation allows the use of smaller inductor and capacitor values.
PAGE 10
LTC3602 APPLICATIONS INFORMATION characteristics. The choice of which style inductor to use mainly depends on the price vs size requirements and any radiated ﬁeld/EMI requirements. New designs for surface mount inductors are available from Coiltronics, Coilcraft, Toko and Sumida. CIN and COUT Selection The input capacitance, CIN, is needed to ﬁlter the trapezoidal current at the source of the top MOSFET.
PAGE 11
LTC3602 APPLICATIONS INFORMATION Burst Clamp Programming If the voltage on the SYNC/MODE pin is less than INTVCC by 1V or more, Burst Mode operation is enabled. During Burst Mode operation, the voltage on the SYNC/MODE pin determines the burst clamp level. This level sets the minimum peak inductor current, IBURST, for each switching cycle according to the following equation: VBURST = IBURST + 0.42V 6A / V VBURST is the voltage on the SYNC/MODE pin. IBURST can be programmed in the range of 0A to 3.
PAGE 12
LTC3602 APPLICATIONS INFORMATION Topside MOSFET Driver Supply (BOOST Pin) The LTC3602 uses a bootstrapped supply to power the gate of the internal topside MOSFET (Figure 3). When the topside MOSFET is off and the SW pin is low, diode DBST charges capacitor CBST to the voltage on the INTVCC supply. In order to turn on the topside MOSFET, the voltage on the BOOST pin is then applied to its gate.
PAGE 13
LTC3602 APPLICATIONS INFORMATION VOUT The VIN operating current loss dominates the efﬁciency loss at very low load currents whereas the I2R loss dominates the efﬁciency loss at medium to high load currents. RB VX VFB RTB LTC3602 RA TRACK/SS RTA 3602 F05a Figure 5a.
PAGE 14
LTC3602 APPLICATIONS INFORMATION Thermal Considerations Checking Transient Response In most applications, the LTC3602 does not dissipate much heat due to its high efﬁciency. But, in applications where the LTC3602 is running at high ambient temperature with low supply voltage and high duty cycles, such as in dropout, the heat dissipated may exceed the maximum junction temperature of the part.
PAGE 15
LTC3602 APPLICATIONS INFORMATION capacitance and a ceramic capacitor in parallel to lower the total effective ESR. For this design, a 100μF ceramic capacitor will be used. CIN should be sized for a maximum current rating of: IRMS = 2.5A • 3.3V 8.4V • – 1 = 1.22ARMS 8.4V 3.3V Decoupling the PVIN pin with a 22μF ceramic capacitor is adequate for most applications.
PAGE 16
LTC3602 TYPICAL APPLICATIONS 1.8V, 2.5A Regulator at 1MHz, Burst Mode Operation CVCC 1μF RPG 200k R3 845k INTVCC SYNC/MODE PGOOD R4 137k CITH 1nF PVIN PGOOD ROSC 105k D1 RT BOOST CBST 0.22μF RITH 4.32k LTC3602 ITH R1 105k CFB 22pF VIN 5V to 10V CIN 22μF R2 210k SW VFB SW RUN SW TRACK/SS PGND PGND PGND L1 1μH VOUT 1.8V 2.
PAGE 17
LTC3602 TYPICAL APPLICATIONS 3.3V, 2.5A Regulator at 2MHz, Forced Continuous, Small Size CVCC 1μF RPG 200k SYNC/MODE PGOOD INTVCC PVIN PGOOD ROSC 47.5k D1 RT CITH 470pF BOOST CBST 0.22μF RITH 2.94k LTC3602 ITH R1 105k CFB 10pF R2 475k VIN 10V CIN 22μF SW VFB SW RUN SW TRACK/SS PGND PGND PGND L1 1μH VOUT 3.3V 2.5A COUT 47μF L1: VISHAY IHLP1616ABER1R0M01 CIN: TAIYO YUDEN EMK316BJ226ML-T COUT: MURATA GRM3ICR60J476ME19 3602 TA04 2.5V, 2.5A Regulator, Synchronized to 1.8MHz 1.
PAGE 18
LTC3602 PACKAGE DESCRIPTION FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BA 4.90 – 5.10* (.193 – .201) 2.74 (.108) 2.74 (.108) 16 1514 13 12 1110 6.60 p 0.10 9 2.74 (.108) 4.50 p 0.10 2.74 6.40 (.108) (.252) BSC SEE NOTE 4 0.45 p 0.05 1.05 p0.10 0.65 BSC 1 2 3 4 5 6 7 8 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.50 – 0.75 (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2.
PAGE 19
LTC3602 PACKAGE DESCRIPTION UF Package 20-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1710 Rev A) 0.70 p 0.05 4.50 p 0.05 3.10 p 0.05 2.00 REF 2.45 p 0.05 2.45 p 0.05 PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.75 p 0.05 4.00 p 0.10 BOTTOM VIEW—EXPOSED PAD R = 0.05 TYP R = 0.115 TYP 19 20 0.40 p 0.10 PIN 1 TOP MARK (NOTE 6) 1 2.45 p 0.10 4.00 p 0.10 PIN 1 NOTCH R = 0.20 TYP OR 0.
PAGE 20
LTC3602 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1877 600mA (IOUT), 550kHz, Synchronous Step-Down DC/DC Converter 96% Efﬁciency, VIN: 2.7V to 10V, VOUT(MIN) = 0.8V, IQ = 10μA, ISD <1μA, MS8 Package LTC1879 1.2A (IOUT), 550kHz, Synchronous Step-Down DC/DC Converter 95% Efﬁciency, VIN: 2.7V to 10V, VOUT(MIN) = 0.8V, IQ = 15μA, ISD <1μA, TTSOP-16 Package LTC3404 600mA (IOUT), 1.4MHz, Synchronous Step-Down DC/DC Converter 95% Efﬁciency, VIN: 2.7V to 6V, VOUT(MIN) = 0.