Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - voltage regulators - DC DC switch controllers SSOP 28

LTC3858-1

38581fd

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Low I

, Dual

2-Phase Synchronous

Step-Down Controller

High Efﬁ ciency Dual 8.5V/3.3V Step-Down Converter

Low Operating I

: 170μA (One Channel On)

Wide Output Voltage Range: 0.8V ≤ V

OUT

≤ 24V

Wide V

Range: 4V to 38V

SENSE

or DCR Current Sensing

Out-of-Phase Controllers Reduce Required Input

Capacitance and Power Supply Induced Noise

OPTI-LOOP

Compensation Minimizes C

OUT

Phase-Lockable Frequency (75kHz-850kHz)

Programmable Fixed Frequency (50kHz-900kHz)

Selectable Continuous, Pulse-Skipping or

Burst Mode

Operation at Light Loads

Very Low Dropout Operation: 99% Duty Cycle

Adjustable Output Voltage Soft-Start

Power Good Output Voltage Monitor

Output Overvoltage Protection

Output Latchoff Protection During Short Circuit

Low Shutdown I

: 8µA

Internal LDO Powers Gate Drive from V

or EXTV

No Current Foldback During Start-Up

Tiny 4mm × 5mm QFN and Narrow SSOP Packages

Automotive Systems

Battery Operated Digital Devices

Distributed DC Power Systems

Efﬁ ciency and Power Loss

vs Load Current

The LTC

3858-1 is a high performance dual step-down

switching regulator controller that drives all N-channel

synchronous power MOSFET stages. A constant frequency

current mode architecture allows a phase-lockable fre-

quency of up to 850kHz. Power loss and noise due to the

input capacitor ESR are minimized by operating the two

controller outputs out of phase.

The 170A no-load quiescent current extends operating

life in battery powered systems. OPTI-LOOP compensa-

tion allows the transient response to be optimized over

a wide range of output capacitance and ESR values. The

LTC3858-1 features a precision 0.8V reference and a power

good output indicator. A wide 4V to 38V input supply range

encompasses a wide range of intermediate bus voltages

and battery chemistries.

Independent soft-start pins for each controller ramp the

output voltages during start-up. The output Latchoff feature

protects the circuit in short-circuit conditions.

For a leadless 32-pin QFN package with the additional fea-

tures of adjustable current limit, clock out, phase modula-

tion and two PGOOD outputs, see the LTC3858 data sheet.

L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, µModule, Linear Technology and the Linear logo

are registered trademarks and No R

SENSE

and UltraFast are trademarks of Linear Technology

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

Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.

0.1µF

62.5k

3.3µH

680pF

150µF

4.7µF

22µF

50V

0.007Ω

20k

15k

OUT1

3.3V

150µF

0.1µF

193k

7.2µH

680pF

0.01Ω

20k

15k

OUT2

8.5V

3.5A

TG1 TG2

BOOST1 BOOST2

SW1 SW2

BG1 BG2

SGND

PGND

SENSE1

SENSE2

SENSE1

–

SENSE2

–

FB1

FB2

TH1

TH2

INTV

SS1 SS2

9V TO 38V

38581 TA01

0.1µF

LTC3858-1

OUTPUT CURRENT (A)

0.0001

EFFICIENCY (%)

POWER LOSS (mW)

0.001 0.01 0.1 1 10

38581 TA01b

100

1000

0.1

10000

EFFICIENCY

POWER LOSS

= 12V

OUT

= 3.3V

FIGURE 12 CIRCUIT

Summary of content (38 pages)

PAGE 1
LTC3858-1 Low IQ, Dual 2-Phase Synchronous Step-Down Controller DESCRIPTION FEATURES n n n n n n n n n n n n n n n n n n The LTC®3858-1 is a high performance dual step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows a phase-lockable frequency of up to 850kHz. Power loss and noise due to the input capacitor ESR are minimized by operating the two controller outputs out of phase.
PAGE 2
LTC3858-1 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (VIN) ......................... –0.3V to 40V Topside Driver Voltages BOOST1, BOOST2 ................................. –0.3V to 46V Switch Voltage (SW1, SW2) ........................ –5V to 40V (BOOST1-SW1), (BOOST2-SW2) ................ –0.3V to 6V RUN1, RUN2 ............................................... –0.3V to 8V Maximum Current Sourced Into Pin from Source >8V...............................................
PAGE 3
LTC3858-1 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating junction temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2). VIN = 12V, VRUN1,2 = 5V, EXTVCC = 0V unless otherwise noted.
PAGE 4
LTC3858-1 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating junction temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2). VIN = 12V, VRUN1,2 = 5V, EXTVCC = 0V unless otherwise noted.
PAGE 5
LTC3858-1 TYPICAL PERFORMANCE CHARACTERISTICS Efﬁciency and Power Loss vs Output Current Efﬁciency vs Load Current 100 90 100 60 30 20 10 0 0.0001 Burst Mode OPERATION 10 PULSESKIPPING MODE 1 FORCED CONTINUOUS MODE 0.1 0.001 0.01 0.1 1 10 OUTPUT CURRENT (A) EFFICIENCY (%) 70 40 80 1000 POWER LOSS (mW) EFFICIENCY (%) FIGURE 12 CIRCUIT 90 VIN = 12V VOUT = 3.3V 80 50 100 10000 VIN = 5V 70 VIN = 12V 60 50 40 30 20 10 0 0.0001 VOUT = 3.3V FIGURE 12 CIRCUIT 0.001 0.01 0.
PAGE 6
LTC3858-1 TYPICAL PERFORMANCE CHARACTERISTICS Total Input Supply Current vs Input Voltage 300μA LOAD 250 200 NO LOAD 150 100 50 5.4 5.2 5.0 10 30 25 20 INPUT VOLTAGE (V) 15 35 EXTVCC RISING 4.8 EXTVCC FALLING 4.6 5.0 4.0 –45 –20 40 80 55 30 TEMPERATURE (°C) 5 0 –20 –150 –200 –250 –300 –350 –400 –450 –500 –550 5% DUTY CYCLE 0 0.2 0.4 0.6 0.8 1.0 ITH PIN VOLTAGE 1.2 1.
PAGE 7
LTC3858-1 TYPICAL PERFORMANCE CHARACTERISTICS Soft-Start Pull-Up Current vs Temperature 1.40 1.20 808 REGULATED FEEDBACK VOLTAGE (mV) 1.35 1.15 1.30 1.10 RUN PIN VOLTAGE (V) SS PULL-UP CURRENT (μA) Regulated Feedback Voltage vs Temperature Shutdown (RUN) Threshold vs Temperature 1.05 1.00 0.95 0.90 1.25 1.20 1.15 1.10 1.05 1.00 0.85 0.95 0.80 –45 –20 80 55 30 TEMPERATURE (°C) 5 105 0.
PAGE 8
LTC3858-1 TYPICAL PERFORMANCE CHARACTERISTICS Latchoff Threshold Voltage vs Temperature INTVCC vs Load Current 5.20 2.3 VIN = 12V 2.2 2.1 INTVCC VOLTAGE (V) INTVCC VOLTAGE (V) 5.15 5.10 EXTVCC = 0V 5.05 EXTVCC = 8V 5.00 ARMING THRESHOLD 2.0 1.9 1.8 1.7 1.6 LATCHOFF THRESHOLD 1.5 1.4 1.3 4.95 0 20 40 60 80 100 120 140 160 180 200 LOAD CURRENT (mA) 3858 G26 PIN FUNCTIONS 1.
PAGE 9
LTC3858-1 PIN FUNCTIONS (QFN/SSOP) INTVCC (Pin 17/Pin 19): Output of the Internal Linear Low Dropout Regulator. The driver and control circuits are powered from this voltage source. Must be decoupled to power ground with a minimum of 4.7μF ceramic or other low ESR capacitor. Do not use the INTVCC pin for any other purpose. EXTVCC (Pin 18/Pin 20): External Power Input to an Internal LDO Connected to INTVCC.
PAGE 10
LTC3858-1 FUNCTIONAL DIAGRAM INTVCC DUPLICATE FOR SECOND CONTROLLER CHANNEL PGOOD1 BOOST DROP OUT DET 0.88V + – VFB1 S Q R Q + 0.72V CB D BOT TOP ON SWITCH LOGIC BOT SHDN CIN SW INTVCC BG COUT – PGND 20μA FREQ DB TG TOP VIN VOUT VCO CLK2 0.425V CLK1 + SLEEP RSENSE L – ICMP PFD + + –+ +– IR – SENSE+ – 3mV SYNC DET PLLIN/MODE 2(VFB) 0.45V SENSE– 100k SLOPE COMP VFB EA – OV – 5.1V 5.1V LDO EN LDO EN 0.80V TRACK/SS 0.88V CC ITH 0.
PAGE 11
LTC3858-1 OPERATION (Refer to the Functional Diagram) INTVCC/EXTVCC Power Power for the top and bottom MOSFET drivers and most other internal circuitry is derived from the INTVCC pin. When the EXTVCC pin is left open or tied to a voltage less than 4.7V, the VIN LDO (low dropout linear regulator) supplies 5.1V from VIN to INTVCC. If EXTVCC is taken above 4.7V, the VIN LDO is turned off and the EXTVCC LDO is turned on. Once enabled, the EXTVCC LDO supplies 5.1V from EXTVCC to INTVCC.
PAGE 12
LTC3858-1 OPERATION (Refer to the Functional Diagram) When a controller is enabled for Burst Mode operation, the minimum peak current in the inductor is set to approximately 30% of the maximum sense voltage even though the voltage on the ITH pin indicates a lower value. If the average inductor current is higher than the load current, the error ampliﬁer, EA, will decrease the voltage on the ITH pin. When the ITH voltage drops below 0.
PAGE 13
LTC3858-1 OPERATION (Refer to the Functional Diagram) operation is maintained down to approximately 1% of designed maximum output current. At very light loads, the current comparator, ICMP, may remain tripped for several cycles and force the external top MOSFET to stay off for the same number of cycles (i.e., skipping pulses). The inductor current is not allowed to reverse (discontinuous operation).
PAGE 14
LTC3858-1 OPERATION (Refer to the Functional Diagram) With 2-phase operation, the two channels of the dual switching regulator are operated 180 degrees out of phase. This effectively interleaves the current pulses drawn by the switches, greatly reducing the overlap time where they add together. The result is a signiﬁcant reduction in total RMS input current, which in turn allows less expensive input capacitors to be used, reduces shielding requirements for EMI and improves real world operating efﬁciency.
PAGE 15
LTC3858-1 APPLICATIONS INFORMATION The Typical Application on the ﬁrst page is a basic LTC3858-1 application circuit. LTC3858-1 can be conﬁgured to use either DCR (inductor resistance) sensing or low value resistor sensing. The choice between the two current sensing schemes is largely a design tradeoff between cost, power consumption and accuracy. DCR sensing is becoming popular because it saves expensive current sensing resistors and is more power efﬁcient, especially in high current applications.
PAGE 16
LTC3858-1 APPLICATIONS INFORMATION Low Value Resistors Current Sensing A typical sensing circuit using a discrete resistor is shown in Figure 5a. RSENSE is chosen based on the required output current. The current comparator has a maximum threshold VSENSE(MAX) of 50mV (typ). The current comparator threshold voltage sets the peak of the inductor current, yielding a maximum average output current, IMAX, equal to the peak value less half the peak-to-peak ripple current, ∆IL.
PAGE 17
LTC3858-1 APPLICATIONS INFORMATION The maximum power loss in R1 is related to duty cycle, and will occur in continuous mode at the maximum input voltage: PLOSS R1= ( VIN(MAX) – VOUT ) • VOUT R1 30% of the current limit determined by RSENSE. Lower inductor values (higher ∆IL) will cause this to occur at lower load currents, which can cause a dip in efﬁciency in the upper range of low current operation. In Burst Mode operation, lower inductance values will cause the burst frequency to decrease.
PAGE 18
LTC3858-1 APPLICATIONS INFORMATION Selection criteria for the power MOSFETs include the onresistance, RDS(ON), Miller capacitance, CMILLER, input voltage and maximum output current. Miller capacitance, CMILLER, can be approximated from the gate charge curve usually provided on the MOSFET manufacturers’ data sheet. CMILLER is equal to the increase in gate charge along the horizontal axis while the curve is approximately ﬂat divided by the speciﬁed change in VDS.
PAGE 19
LTC3858-1 APPLICATIONS INFORMATION Equation 1 has a maximum at VIN = 2VOUT , where IRMS = IOUT/2. This simple worst-case condition is commonly used for design because even signiﬁcant deviations do not offer much relief. Note that capacitor manufacturers’ ripple current ratings are often based on only 2000 hours of life. This makes it advisable to further derate the capacitor, or to choose a capacitor rated at a higher temperature than required.
PAGE 20
LTC3858-1 APPLICATIONS INFORMATION linear ramping voltage at the SS pin. The LTC3858-1 will regulate the VFB pin (and hence VOUT) according to the voltage on the SS pin, allowing VOUT to rise smoothly from 0V to its ﬁnal regulated value. The total soft-start time will be approximately: tSS = CSS 0.
PAGE 21
LTC3858-1 APPLICATIONS INFORMATION 1. EXTVCC Left Open (or Grounded). This will cause INTVCC to be powered from the internal 5.1V regulator resulting in an efﬁciency penalty of up to 10% at high input voltages. 2. EXTVCC Connected Directly to VOUT . This is the normal connection for a 5V to 14V regulator and provides the highest efﬁciency. 3. EXTVCC Connected to an External Supply. If an external supply is available in the 5V to 14V range, it may be used to power EXTVCC. Ensure that EXTVCC < VIN. 4.
PAGE 22
LTC3858-1 APPLICATIONS INFORMATION is sensed, the top MOSFET is turned off and the bottom MOSFET is turned on until the overvoltage condition is cleared. The bottom MOSFET remains on continuously for as long as the overvoltage condition persists; if VOUT returns to a safe level, normal operation automatically resumes. 1000 900 FREQUENCY (kHz) 800 A shorted top MOSFET will result in a high current condition which will open the system fuse.
PAGE 23
LTC3858-1 APPLICATIONS INFORMATION Minimum On-Time Considerations Minimum on-time, tON(MIN), is the smallest time duration that the LTC3858-1 is capable of turning on the top MOSFET. It is determined by internal timing delays and the gate charge required to turn on the top MOSFET.
PAGE 24
LTC3858-1 APPLICATIONS INFORMATION 4. Transition losses apply only to the topside MOSFET(s), and become signiﬁcant only when operating at high input voltages (typically 15V or greater). Transition losses can be estimated from: Transition Loss = (1.7) • VIN • 2 • IO(MAX) • CRSS • f Other “hidden” losses such as copper trace and internal battery resistances can account for an additional 5% to 10% efﬁciency degradation in portable systems.
PAGE 25
LTC3858-1 APPLICATIONS INFORMATION should be controlled so that the load rise time is limited to approximately 25 • CLOAD. Thus a 10μF capacitor would require a 250μs rise time, limiting the charging current to about 200mA. Design Example estimated. Choosing a Fairchild FDS6982S dual MOSFET results in: RDS(ON) = 0.035Ω/0.022Ω, CMILLER = 215pF. At maximum input voltage with T(estimated) = 50°C: PMAIN = ( As a design example for one channel, assume VIN = 12V(nominal), VIN = 22V (max), VOUT = 3.
PAGE 26
LTC3858-1 APPLICATIONS INFORMATION When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the IC. These items are also illustrated graphically in the layout diagram of Figure 10. Figure 11 illustrates the current waveforms present in the various branches of the 2-phase synchronous regulators operating in the continuous mode. Check the following in your layout: 1.
PAGE 27
LTC3858-1 APPLICATIONS INFORMATION SS1 LTC3858-1 ITH1 VFB1 RPU1 PGOOD1 VPULL-UP (<6V) PGOOD1 L1 SENSE1+ TG1 SENSE1– SW1 VOUT1 CB1 FREQ RSENSE M1 BOOST1 M2 D1 BG1 PLLIN/MODE RUN1 VIN CVIN RIN GND + INTVCC SENSE2+ BG2 VOUT1 CINTVCC VIN CIN COUT2 1μF CERAMIC M3 BOOST2 + EXTVCC SENSE2– VFB2 COUT1 PGND RUN2 SGND 1μF CERAMIC + fIN M4 D2 CB2 ITH2 SS2 SW2 RSENSE TG2 VOUT2 L2 38581 F10 Figure 10.
PAGE 28
LTC3858-1 APPLICATIONS INFORMATION SW1 L1 D1 RSENSE1 VOUT1 COUT1 RL1 VIN RIN CIN SW2 BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. D2 L2 RSENSE2 VOUT2 COUT2 RL2 38581 F11 Figure 11. Branch Current Waveforms path voltage pickup between these components and the SGND pin of the IC. An embarrassing problem, which can be missed in an otherwise properly working switching regulator, results when the current sensing leads are hooked up backwards.
PAGE 29
LTC3858-1 TYPICAL APPLICATIONS RB1 215k CF1 15pF LTC3858-1 SENSE1+ C1 1nF RA1 68.1k SENSE1– VFB1 CITH1A 150pF INTVCC 100k PGOOD1 MBOT1 BG1 SW1 ITH1 RSENSE1 7mΩ CB1 0.47μF BOOST1 RITH1 15k COUT1 150μF VOUT1 3.3V 5A MTOP1 TG1 D1 CITH1 820pF CSS1 0.1μF VIN CIN 22μF SS1 INTVCC PGND PLLIN/MODE SGND TG2 EXTVCC RUN1 BOOST2 RUN2 FREQ SS2 SW2 ITH2 BG2 VIN 9V TO 38V CINT 4.7μF D2 MTOP2 CB2 0.47μF L2 7.2μH CSS2 0.1μF CITH2 680pF L1 3.3μH RSENSE2 10mΩ RITH2 27k CITH2A 100pF RA2 44.
PAGE 30
LTC3858-1 TYPICAL APPLICATIONS High Efﬁciency Dual 2.5V/3.3V Step-Down Converter RB1 143k CF1 22pF RA1 68.1k C1 1nF LTC3858-1 SENSE1+ SENSE1– VFB1 CITH1A 100pF INTVCC 100k PGOOD1 MBOT1 BG1 SW1 ITH1 CITH1 820pF RSENSE1 7mΩ CB1 0.47μF BOOST1 RITH1 22k D1 CSS1 0.01μF VIN CIN 22μF INTVCC PGND PLLIN/MODE SGND TG2 EXTVCC RUN1 BOOST2 RUN2 FREQ SS2 SW2 ITH2 BG2 VIN 4V TO 38V CINT 4.7μF D2 MTOP2 CB2 0.47μF L2 3.2μH CSS2 0.01μF RSENSE2 7mΩ RITH2 15k CITH2A 150pF RA2 68.1k COUT1 150μF VOUT1 2.
PAGE 31
LTC3858-1 TYPICAL APPLICATIONS High Efﬁciency Dual 12V/5V Step-Down Converter RB1 422k CF1 33pF RA1 30.1k C1 1nF SENSE1+ SENSE1– INTVCC 100k PGOOD1 MBOT1 BG1 VFB1 CITH1A 100pF SW1 CITH1 680pF D1 LTC3858-1 SS1 VIN INTVCC PGND PLLIN/MODE SGND TG2 EXTVCC RUN1 BOOST2 RUN2 FREQ RFREQ 60k CIN 22μF CINT 4.7μF SS2 SW2 ITH2 BG2 VIN 12.5V TO 38V D2 MTOP2 CB2 0.47μF L2 4.3μH CSS2 0.
PAGE 32
LTC3858-1 TYPICAL APPLICATIONS High Efﬁciency Dual 24V/5V Step-Down Converter RB1 487k CF1 18pF RA1 16.9k C1 1nF SENSE1+ SENSE1– INTVCC 100k PGOOD1 MBOT1 BG1 VFB1 CITH1A 100pF SW1 CITH1 680pF MTOP1 TG1 ITH1 CSS1 0.01μF D1 LTC3858-1 SS1 VIN INTVCC PGND PLLIN/MODE SGND TG2 EXTVCC RUN1 BOOST2 RUN2 FREQ RFREQ 60k RSENSE1 25mΩ CB1 0.47μF BOOST1 RITH1 46k CIN 22μF CINT 4.7μF SS2 SW2 ITH2 BG2 RA2 75k MTOP2 CB2 0.47μF L2 4.
PAGE 33
LTC3858-1 TYPICAL APPLICATIONS High Efﬁciency Dual 1V/1.2V Step-Down Converter RB1 28.7k CF1 56pF RA1 115k C1 1nF SENSE1+ SENSE1– INTVCC 100k PGOOD1 L1 MBOT1 0.47μH BG1 VFB1 CITH1A 220pF SW1 CITH1 1000pF VIN CIN 22μF SS1 INTVCC PGND PLLIN/MODE SGND TG2 EXTVCC RUN1 BOOST2 RUN2 FREQ RFREQ 60k SS2 SW2 ITH2 BG2 D2 MTOP2 CB2 0.47μF L2 0.47μH RITH2 3.43k CITH2A 220pF RA2 115k VFB2 SENSE2– CF2 56pF RB2 57.6k C2 1nF SENSE2+ VIN 12V CINT 4.7μF CSS2 0.
PAGE 34
LTC3858-1 TYPICAL APPLICATIONS High Efﬁciency Dual 1V/1.2V Step-Down Converter with Inductor DCR Current Sensing RB1 28.7k CF1 56pF RA1 115k RS1 1.18k C1 0.1μF SENSE1+ SENSE1– INTVCC 100k PGOOD1 CITH1A 200pF SW1 CITH1 1000pF VIN CIN 22μF SS1 INTVCC PGND PLLIN/MODE SGND TG2 EXTVCC RUN1 BOOST2 RUN2 FREQ RFREQ 65k SS2 SW2 ITH2 BG2 VIN 12V CINT 4.7μF D2 MTOP2 CB2 0.47μF L2 0.47μH CSS2 0.01μF VOUT2 1.2V COUT2 8A 220μF ×2 RITH2 3.93k CITH2A 220pF RA2 115k CF2 56pF RB2 57.
PAGE 35
LTC3858-1 PACKAGE DESCRIPTION UFD Package 28-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1712 Rev B) 0.70 p0.05 4.50 p 0.05 3.10 p 0.05 2.50 REF 2.65 p 0.05 3.65 p 0.05 PACKAGE OUTLINE 0.25 p0.05 0.50 BSC 3.50 REF 4.10 p 0.05 5.50 p 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 p 0.10 (2 SIDES) 0.75 p 0.05 R = 0.05 TYP PIN 1 NOTCH R = 0.20 OR 0.35 s 45o CHAMFER 2.50 REF R = 0.115 TYP 27 28 0.40 p 0.
PAGE 36
LTC3858-1 PACKAGE DESCRIPTION GN Package 28-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .386 – .393* (9.804 – 9.982) .045 p.005 28 27 26 25 24 23 22 21 20 19 18 17 1615 .254 MIN .033 (0.838) REF .150 – .165 .229 – .244 (5.817 – 6.198) .0165 p.0015 .150 – .157** (3.810 – 3.988) .0250 BSC 1 RECOMMENDED SOLDER PAD LAYOUT .015 p .004 s 45o (0.38 p 0.10) .0075 – .0098 (0.19 – 0.25) 2 3 4 5 6 7 8 .0532 – .0688 (1.35 – 1.75) 9 10 11 12 13 14 .004 – .0098 (0.102 – 0.
PAGE 37
LTC3858-1 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 11/09 Change to Absolute Maximum Ratings Change to Electrical Characteristics Change to Typical Performance Characteristics Change to Pin Functions Text Changes to Operation Section Text Changes to Applications Information Section C D 08/10 12/10 2 3, 4 6 8, 9 11, 12, 13 20, 21, 22, 23, 25 Change to Table 2 22 Change to Figure 10 27 Changes to Related Parts 38 Changes to Electrical Characterist
PAGE 38
LTC3858-1 TYPICAL APPLICATION High Efﬁciency 2-Phase 12V/150W Step-Down Converter RB1 698k CF1 10pF RA1 49.9k SENSE1+ C1 1nF SENSE1– INTVCC 100k PGOOD1 MBOT1 BG1 VFB1 CITH1A 68pF L1 6μH 10μF 16V SW1 CITH1 3300pF MTOP1 TG1 ITH1 D1 LTC3858-1 CSS1 0.1μF VIN CIN 10μF 50V SS1 INTVCC VOUT SS1 ITH1 VFB1 10μF 50V VIN 19V TO 28V D2 MTOP2 CB2 0.47μF L2 6μH RSENSE2 5mΩ COUT2 22μF 16V MBOT2 BG2 VFB2 SENSE2– C2 1nF CINT 4.