Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Holder DFN 16

LTC3417

3417fd

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Dual Synchronous

1.4A/800mA 4MHz

Step-Down DC/DC Regulator

The LTC

3417 is a dual constant frequency, synchronous

step-down DC/DC converter. Intended for medium power

applications, it operates from a 2.25V to 5.5V input volt-

age range and has a constant programmable switching

frequency, allowing the use of tiny, low cost capacitors

and inductors 2mm or less in height. Each output voltage

is adjustable from 0.8V to 5V. Internal synchronous low

DS(ON)

power switches provide high efﬁ ciency without

the need for external Schottky diodes.

A user selectable mode input allows the user to trade

off ripple voltage for light load efﬁ ciency. Burst Mode

operation provides high efﬁ ciency at light loads, while

Pulse Skip mode provides low ripple noise at light loads.

A phase mode pin allows the second channel to operate

in-phase or 180° out-of-phase with respect to channel 1.

Out-of-phase operation produces lower RMS current on

and thus lower RMS derating on the input capacitor.

To further maximize battery life, the P-channel MOSFETs

are turned on continuously in dropout (100% duty cycle)

and both channels draw a total quiescent current of only

125µA. In shutdown, the device draws <1µA.

OUT2 Efﬁ ciency

(Burst Mode Operation)

High Efﬁ ciency: Up to 95%

1.4A/800mA Guaranteed Minimum Output Current

No Schottky Diodes Required

Programmable Frequency Operation: 1.5MHz or

Adjustable From 0.6MHz to 4MHz

Low R

DS(ON)

Internal Switches

Short-Circuit Protected

: 2.25V to 5.5V

Current Mode Operation for Excellent Line and

Load Transient Response

125µA Quiescent Current in Sleep Mode

Ultralow Shutdown Current: I

< 1µA

Low Dropout Operation: 100% Duty Cycle

Power Good Output

Phase Pin Selects 2nd Channel Phase Relationship

with Respect to 1st Channel

Internal Soft-Start with Individual Run Pin Control

Available in Small Thermally Enhanced

(5mm × 3mm) DFN and 20-Lead TSSOP Packages

PDAs/Palmtop PCs

Digital Cameras

Cellular Phones

PC Cards

Wireless and DSL Modems

L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners. Protected by U.S. Patents

including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131, 6144194.

FREQ

SW1

RUN1

FB1

TH1

SW2

RUN2

FB2

TH2

LTC3417

GND

10µF

1.5µH

2.2µH

22pF

511k

22pF

866k

412k

10µF

5.9k 2.87k

2200pF

6800pF

3417 TA01

22µF

OUT1

1.8V

1.4A

OUT2

2.5V

800mA

2.5V TO 5.5V

LOAD CURRENT (A)

0.001

EFFICIENCY (%)

100

0.01 0.1 1

3417 TA01a

POWER LOSS (W)

0.001

0.01

0.1

0.0001

EFFICIENCY

REFER TO FIGURE 4

POWER LOSS

= 3.6V

OUT

= 2.5V

FREQ = 1MHz

Summary of content (20 pages)

PAGE 1
LTC3417 Dual Synchronous 1.4A/800mA 4MHz Step-Down DC/DC Regulator DESCRIPTION FEATURES n n n n n n n n n n n n n n n High Efﬁciency: Up to 95% 1.4A/800mA Guaranteed Minimum Output Current No Schottky Diodes Required Programmable Frequency Operation: 1.5MHz or Adjustable From 0.6MHz to 4MHz Low RDS(ON) Internal Switches Short-Circuit Protected VIN: 2.25V to 5.
PAGE 2
LTC3417 ABSOLUTE MAXIMUM RATINGS (Note 1) VIN1, VIN2 Voltages ...................................... – 0.3V to 6V MODE, SW1, SW2, RUN1, RUN2, VFB1, VFB2, PHASE, FREQ, ITH1, ITH2 Voltages............... –0.3V to (VIN1/VIN2 + 0.3V) VIN1 – VIN2, VIN2 – VIN1 .......................................... 0.3V PGOOD Voltage ........................................... –0.3V to 6V Operating Ambient Temperature Range (Note 2) ..................................................
PAGE 3
LTC3417 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 3.6V unless otherwise speciﬁed. (Note 2) SYMBOL PARAMETER CONDITIONS gm(EA) Error Ampliﬁer Transconductance ITH1, ITH2(PINLOAD) = ±5μA (Note 3) MIN 1400 TYP MAX UNITS IS Input DC Supply Current (Note 4) Active Mode VFB1 = VFB2 = 0.75V, VMODE = VIN, VRUN1 = VRUN2 = VIN 400 600 μA Half Active Mode (VRUN2 = 0V, 1.
PAGE 4
LTC3417 TYPICAL PERFORMANCE CHARACTERISTICS OUT1 Pulse Skipping Mode Operation OUT1 Burst Mode Operation OUT1 Forced Continuous Mode Operation VOUT 20mV/DIV VOUT 20mV/DIV VOUT 20mV/DIV IL 250mA/DIV IL 250mA/DIV IL 250mA/DIV 3417 G01 VIN = 3.6V 2μs/DIV VOUT = 1.8V ILOAD = 100mA REFER TO FIGURE 4 3417 G02 2μs/DIV VIN = 3.6V VOUT = 1.
PAGE 5
LTC3417 TYPICAL PERFORMANCE CHARACTERISTICS OUT2 Efﬁciency vs VIN (Pulse Skipping Mode) Load Step OUT1 Load Step OUT2 100 ILOAD = 250mA EFFICIENCY (%) 95 VOUT1 100mV/DIV VOUT2 100mV/DIV IOUT1 500mA/DIV IOUT2 500mA/DIV ILOAD = 800mA 90 85 80 75 70 2 2.5 3 3.5 4 4.5 5 3417 G11 VIN = 3.6V 100μs/DIV VOUT = 1.8V ILOAD = 0.25A to 1.4A REFER TO FIGURE 4 VOUT = 2.5V REFER TO FIGURE 4 5.5 3417 G12 VIN = 3.6V 100μs/DIV VOUT = 2.5V ILOAD = 0.25A to 0.
PAGE 6
LTC3417 PIN FUNCTIONS (DFN/TSOP) RUN1 (Pin 1/Pin 2): Enable for 1.4A Regulator. When at Logic 1, 1.4A regulator is running. When at 0V, 1.4A regulator is off. When both RUN1 and RUN2 are at 0V, the part is in shutdown. VIN1 (Pin 2/Pin 3): Supply Pin for P-channel Switch of 1.4A Regulator. ITH1 (Pin 3/Pin 4): Error Ampliﬁer Compensation Point for 1.4A Regulator. The current comparator threshold increases with this control voltage. Nominal voltage range for this pin is 0V to 1.5V.
PAGE 7
LTC3417 FUNCTIONAL DIAGRAM 1.4A REGULATOR ITH1 + VFB1 – – VIN1 ITH LIMIT + + – VB 0.752V SLOPE COMPENSATION + ANTI-SHOOTTHROUGH – SW1 + + LOGIC 0.848V – – – + PGND1 RUN1 PGOOD VOLTAGE REFERENCE VIN2 RUN2 PHASE MODE OSCILLATOR FREQ PGND2 + – – LOGIC + – 0.848V + – SW2 ANTI-SHOOTTHROUGH 0.
PAGE 8
LTC3417 OPERATION The LTC3417 uses a constant frequency, current mode architecture. Both channels share the same clock frequency. The PHASE pin sets whether the channels are running in-phase or out of phase. The operating frequency is determined by connecting the FREQ pin to VIN for 1.5MHz operation or by connecting a resistor from FREQ to ground for a frequency from 0.6MHz to 4MHz. To suit a variety of applications, the MODE pin allows the user to trade off noise for efﬁciency.
PAGE 9
LTC3417 APPLICATIONS INFORMATION A general LTC3417 application circuit is shown in Figure 4. External component selection is driven by the load requirement, and begins with the selection of the inductors L1 and L2. Once L1 and L2 are chosen, CIN, COUT1 and COUT2 can be selected. 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
LTC3417 APPLICATIONS INFORMATION Inductor Core Selection Different core materials and shapes will change the size/current relationship of an inductor. Toroid or shielded pot cores in ferrite or permalloy materials are small and don’t radiate much energy, but generally cost more than powdered iron core inductors with similar electrical characteristics.
PAGE 11
LTC3417 APPLICATIONS INFORMATION When D1 = D2 then the equation simpliﬁes to: IRMS = (I1 +I2 ) D (1– D) or IRMS = (I1 +I2 ) VOUT ( VIN – VOUT ) VIN where the maximum average output currents I1 and I2 equal the respective peak currents minus half the peakto-peak ripple currents: I I1 =ILIM1 – L1 2 I I2 =ILIM2 – L2 2 These formula have a maximum at VIN = 2VOUT, where IRMS = (I1 + I2)/2. This simple worst case is commonly used to determine the highest IRMS.
PAGE 12
LTC3417 APPLICATIONS INFORMATION is given to ripple current ratings and long term reliability. Ceramic capacitors have the lowest ESR and cost but also have the lowest capacitance density, high voltage and temperature coefﬁcient and exhibit audible piezoelectric effects. In addition, the high Q of ceramic capacitors along with trace inductance can lead to signiﬁcant ringing. Other capacitor types include the Panasonic specialty polymer (SP) capacitors. In most cases, 0.
PAGE 13
LTC3417 APPLICATIONS INFORMATION VRUN 2V/DIV VRUN 2V/DIV VOUT 1V/DIV VOUT 1V/DIV IL 1A/DIV IL 0.5A/DIV VIN = 3.6V VOUT = 1.8V RL = 0.9Ω 200μs/DIV Figure 2. Digital Soft-Start Out1 VIN = 3.6V VOUT = 2.5V RL = 2Ω 200μs/DIV Figure 3. Digital Soft-Start Out2 Soft-Start Checking Transient Response Soft-start reduces surge currents from VIN by gradually increasing the peak inductor current. Power supply sequencing can also be accomplished by controlling the ITH pin.
PAGE 14
LTC3417 APPLICATIONS INFORMATION Switching regulators take several cycles to respond to a step in load current. When a load step occurs, VOUT immediately shifts by an amount equal to ΔILOAD • ESRCOUT, where ESRCOUT is the effective series resistance of COUT. ΔILOAD also begins to charge or discharge COUT generating a feedback error signal used by the regulator to return VOUT to its steady-state value.
PAGE 15
LTC3417 APPLICATIONS INFORMATION 3) I2R losses are calculated from the DC resistances of the internal switches, RSW, and the external inductor, RL. In continuous mode, the average output current ﬂowing through inductor L is “chopped” between the internal top and bottom switches.
PAGE 16
LTC3417 APPLICATIONS INFORMATION Design Example As a design example, consider using the LTC3417 in a portable application with a Li-Ion battery. The battery provides a VIN from 2.5V to 4.2V. One output requires 1.8V at 1.3A in active mode, and 1mA in standby mode. The other output requires 2.5V at 700mA in active mode, and 500μA in standby mode. Since both loads still need power in standby, Burst Mode operation is selected for good low load efﬁciency (MODE = VIN).
PAGE 17
LTC3417 APPLICATIONS INFORMATION VIN 2.25V TO 5.5V CIN 10μF CIN2 0.1μF CIN1 0.1μF R7 100k VIN1 VIN2 VOUT1 1.8V 1.4A L1 1.5μH MODE SW1 C1 22pF VIN SW2 RUN1 RUN2 C2 22pF VIN LTC3417 R1 511k COUT1 22μF L2 2.2μH PGOOD VFB1 R2 412k PHASE VOUT2 2.5V 800mA R3 866k VFB2 FREQ R4 412k VIN ITH1 R5 5.9k ITH2 EXPOSED GNDA PAD GNDD COUT2 10μF R6 2.
PAGE 18
LTC3417 APPLICATIONS INFORMATION Board Layout Considerations must be connected between the (+) plate of COUT2 and a ground line terminated near GNDA. The feedback signals VFB1 and VFB2 should be routed away from noise components and traces, such as the SW lines, and its trace should be minimized. When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3417. These items are also illustrated graphically in the layout diagram of Figure 5.
PAGE 19
LTC3417 PACKAGE DESCRIPTION DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 0.65 ±0.05 3.50 ±0.05 1.65 ±0.05 2.20 ±0.05 (2 SIDES) 9 3.00 ±0.10 (2 SIDES) PACKAGE OUTLINE PIN 1 NOTCH 8 0.75 ±0.05 0.200 REF 4.40 ±0.05 (2 SIDES) 1 0.25 ± 0.05 0.50 BSC (DHC16) DFN 1103 4.40 ±0.10 (2 SIDES) 0.00 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 0.40 ± 0.10 16 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) 0.25 ± 0.05 0.
PAGE 20
LTC3417 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3404 600mA (IOUT), 1.4MHz, Synchronous Step-Down DC/DC Converter 95% Efﬁciency, VIN: 2.7V to 6V, VOUT(MIN) = 0.8V, IQ = 10μA, ISD < 1μA, MS8 Package LTC3405/LTC3405A 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converters 95% Efﬁciency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 20μA, ISD < 1μA, ThinSOT™ Package LTC3406/LTC3406B 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converters 96% Efﬁciency, VIN: 2.5V to 5.