LTC3862 LINER [Linear Technology], LTC3862 Datasheet
LTC3862
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LTC3862 Summary of contents
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... SENSE1 GATE2 + SENSE2 0.006Ω – SENSE2 PGND CLKOUT SLOPE D MAX 3862 TA01 LTC3862 3862 is a two phase constant frequency, current 36V V OUT Effi ciency vs Output Current 48V 5A (MAX 48V OUT 12V ...
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... ITH Voltage ............................................... –0.3V to 2.7V FB Voltage .................................................. –0.3V to 3V8 FREQ Voltage ............................................ –0.3V to 1.5V Operating Junction Temperature Range (Notes 3, 4) LTC3862E ............................................. –40°C to 85°C LTC3862I............................................ –40°C to 125°C LTC3862H .......................................... –40°C to 150°C Storage Temperature Range ................... –65°C to 150°C Refl ow Peak Body Temperature ........................... 260°C ...
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... SLOPE l (Note Float, Low Duty Cycle (Note 3) SLOPE (V – SENSE1 SENSE2 RUN V = 1.5V RUN RUN R = 45.6k FREQ 45.6k FREQ 45.6k FREQ LTC3862 MIN TYP MAX UNITS 1.8 3 μA 4.8 5.0 5.2 V 0.002 0.02 %/V –2 % 3.3 V 2.9 V 3.8 V 1.210 1.223 1.235 V 1.199 1.223 1.248 V ± ...
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... The LTC3862I is guaranteed over the full –40°C to 125°C operating junction temperature range and the LTC3862H is guaranteed over the full –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125° ...
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... LOAD Shutdown Quiescent Current vs Input Voltage 150 INPUT VOLTAGE (V) LTC3862 4000 EFFICIENCY 3500 3000 2500 POWER LOSS 2000 = 48V OUT = 1A OUT 1500 INPUT VOLTAGE (V) 3862 G02 Quiescent Current vs Input Voltage 3.00 2.75 2 ...
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... LTC3862 TYPICAL PERFORMANCE CHARACTERISTICS INTV Line Regulation CC 5.25 5.00 4. INPUT VOLTAGE (V) 3962 G09 INTV LDO Dropout vs Load CC Current, Temperature 1600 1400 150°C 1200 125°C 1000 85°C 800 25°C 600 –40°C 400 200 INTV LOAD (mA) ...
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... TEMPERATURE (°C) Soft-Start Current vs Soft-Start Voltage 0 –1 –2 –3 –4 –5 –6 150 0 0.5 1 1.5 2 2.5 3 SOFT-START VOLTAGE (V) LTC3862 RUN Threshold vs Input Voltage 1.5 1.4 1.3 ON 1.2 OFF 1.1 1 INPUT VOLTAGE (V) 3862 G09 RUN Source Current vs Input Voltage 0 –1 –2 –3 – ...
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... LTC3862 TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency vs Input Voltage 320 315 310 305 300 295 290 285 280 INPUT VOLTAGE (V) 3862 G27 Frequency Voltage vs Temperature 1.235 1.233 1.231 1.229 1.227 1.225 1.223 1.221 1.219 1.217 1.215 1.213 1.211 ...
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... FB: Error Amplifi er Input. The FB pin should be connected through a resistive divider network to V output voltage. FREQ: A resistor from FREQ to SGND sets the operating frequency. GATE1, GATE2: Gate Drive Output. The LTC3862 provides a 5V gate drive referenced to PGND to drive a logic-level threshold MOSFET. INTV : Output of the Internal 5V Low Dropout Regulator CC (LDO). A low ESR 4.7μ ...
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... LTC3862 PIN FUNCTIONS + + SENSE1 , SENSE2 : Positive Inputs to the Current Comparators. The ITH pin voltage programs the current comparator offset in order to set the peak current trip threshold. This pin is normally connected to a sense resistor in the source of the power MOSFET. – – SENSE1 ...
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... MAX BLOGIC PWM LATCH + OV ITRIP R ICMP LOOP PSKIP – RUN EA – – 4.5μA + – 1.223V 1.345V 1.22V LTC3862 LDO INTV CC C VCC 3.8V LDO L 3V8 C 3V8 BIAS D GATE + M LOGIC C OUT PGND SENSE – ...
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... An undervoltage lockout (UVLO) circuit senses the INTV regulator output in order to protect the power MOSFETs from operating with inadequate gate drive. For the LTC3862 the rising UVLO threshold is typically 3.3V and the hyster- esis is typically 400mV. The LTC3862 was optimized for logic-level power MOSFETs and applications where the output voltage is less than 50V to 60V ...
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... IC pins. This LDO is not intended to be used as a supply for external circuitry. Thermal Considerations and Package Options The LTC3862 is offered in two package options. The 5mm × 5mm QFN package (UH24) has a thermal resistance R of 34°C/W, the 24-pin TSSOP (FE24) package has a TH(JA) thermal resistance of 38° ...
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... Operation at Low Supply Voltage The LTC3862 has a minimum input voltage of 4V, making it a good choice for applications that experience low sup- ply conditions. The gate driver for the LTC3862 consists ...
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... Figure 3. Using the LTC3862 with an External Bias Supply Power Supply Sequencing As shown in Figure 1, there are body diodes in parallel with the PMOS output transistors in the two LDO regula- tors in the LTC3862 result not possible to bias the INTV and V pins of the chip from separate power ...
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... LTC3862 OPERATION Operation of the RUN Pin The control circuitry in the LTC3862 is turned on and off using the RUN pin. Pulling the RUN pin below 1.22V forces shutdown mode and releasing it allows a 0.5μA current source to pull this pin up, allowing a “normally on” converter to be designed. Alternatively, the RUN pin can be externally pulled up or driven directly by logic ...
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... R = 5.5096E9(f ) FREQ OSC A phase-lock loop is available on the LTC3862 to syn- chronize the internal oscillator to an external clock source connected to the SYNC pin. Connect a series RC network from the PLLFLTR pin to SGND to compensate PLL’s feedback loop. Typical compensation components are a 0.01μF capacitor in series with a 10k resistor. The PLLFLTR pin is both the output of the phase detector and the input to the voltage controlled oscillator (VCO) ...
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... Soft-Start The start-up of the LTC3862 is controlled by the voltage on the SS pin. An internal PNP transistor clamps the current comparator sense threshold during soft-start, thereby limiting the peak switch current. The base of the PNP is ...
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... F09a used, the internal ramp compensation could be inadequate to prevent sub-harmonic oscillation. The LTC3862 contains a pin that allows the user to program the slope compensation gain in order to optimize perfor- mance for a wider range of inductance. With the SLOPE pin left fl oating, the normalized slope gain is 1.00. Con- necting the SLOPE pin to ground reduces the normalized gain to 0 ...
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... Figure 12. Effect of Slope Gain on the Peak SENSE Threshold 20 Programmable Blanking and the Minimum On-Time The BLANK pin on the LTC3862 allows the user to program the amount of leading edge blanking at the SENSE pins. Connecting the BLANK pin to SGND results in a minimum on-time of 180ns, fl oating the pin increases this time to 260ns, and connecting the BLANK pin to the 3V8 supply results in a minimum on-time of 340ns ...
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... Figure 13. Leading Edge Blanking Effects on the Minimum On-Time In order to satisfy these different applications require- ments, the LTC3862 has a simple way to program the maximum duty cycle. Connecting the D limits the maximum duty cycle to 96%. Floating this pin limits the duty cycle to 84% and connecting the D to the 3V8 supply limits it to 75% ...
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... SENSE and SENSE be less than 1μA. Since the LTC3862 contains leading edge blanking, an external RC fi lter is not required for proper operation. However external fi lter is used, the fi lter components should be placed close to the SENSE the IC, as shown in Figure 15. The positive and negative ...
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... Figure 17 illustrates the load step response of a properly compensated boost converter. I LOAD 5A/DIV I L1 5A/DIV I L2 5A/DIV V OUT V = 24V 500μs/DIV 48V OUT Figure 17. Load Step Response of a Properly Compensated Boost Converter LTC3862 and the bandwidth decreased, the C 3862 F17 . 3862fb 23 ...
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... LTC3862 APPLICATIONS INFORMATION Typical Boost Applications Circuit A basic 2-phase, single output LTC3862 application circuit is shown in Figure 18. External component selection is driven by the characteristics of the load and the input supply. Duty Cycle Considerations For a boost converter operating in a continuous conduction mode (CCM), the duty cycle of the main switch is: ⎛ ...
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... Peak and Average Input Currents The control circuit in the LTC3862 measures the input current (by means of resistors in the sources of the power MOSFETs), so the output current needs to be refl ected back to the input in order to dimension the power MOSFETs properly ...
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... R is specifi ed for a voltage less than or equal to the nominal INTV voltage of 5V. For applications that require a power CC MOSFET rated 10V, please refer to the LTC3862-1 ) data sheet. Also pay close attention to the BV the MOSFETs relative to the maximum actual switch volt- age in the application ...
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... MOSFETs. DS(ON) Programming the Current Limit The peak sense voltage threshold for the LTC3862 is 75mV at low duty cycle and with a normalized slope gain of 1.00, and is measured from SENSE illustrates the change in the sense threshold with varying duty cycle and slope gain ...
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... LTC3862 APPLICATIONS INFORMATION For a boost converter where the current limit value is chosen to be 30% higher than the maximum load current, the peak current in the MOSFET and sense resistor is: ⎛ • 1 ⎝ ⎜ SW MAX ( ) R SENSE ( ) n The sense resistor value is then • • – ...
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... SW1 50V/DIV SW2 50V/DIV I 2A/DIV L1 I 2A/DIV L2 V OUT 50mV/DIV V = 10V 1μs/DIV 48V OUT 500mA LOAD Figure 22. Switching Waveforms for a Boost Converter LTC3862 • V ≤ OUT I D PEAK ( ) ⎛ χ ⎞ MAX ( ) = + • 1 • ...
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... LTC3862 APPLICATIONS INFORMATION For the bulk capacitance, which we assume contributes 1% to the total output ripple, the minimum required ca- pacitance is approximately MAX ( ) ≥ C OUT • • • f OUT For many designs it will be necessary to use one type of capacitor to obtain the required ESR, and another type to satisfy the bulk capacitance ...
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... DUTY CYCLE Figure 24. Normalized Input Peak-to-Peak Ripple Current A Design Example Consider the LTC3862 application circuit is shown in Fig- ure 25a. The output voltage is 48V and the input voltage range 36V. The maximum output current is 5A when the input voltage is 24V to 36V. Below 24V, current limit will linearly reduce the maximum load (see Figure 25b) ...
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... LTC3862 APPLICATIONS INFORMATION D MAX SLOPE BLANK PHASEMODE 45.3k FREQ 10nF SS 4.7nF LTC3862 30.1k ITH 100pF FB 12.4k SGND 475k V OUT CLKOUT SYNC PLLFLTR Figure 25a 36V Input, 48V/5A Output 2-Phase Boost Converter Application Circuit INPUT VOLTAGE (V) Figure 25b. Output Current vs Input Voltage 4 ...
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... The maximum current sense threshold for the LTC3862 is 75mV at low duty cycle and a normalized slope gain of 1.0. Using Figure 20, the maximum sense voltage drops to 73mV at a duty cycle of 51% with a normal- ized slope gain the sense resistor is calculated ...
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... F26 7. Place the small-signal components away from high frequency switching nodes on the board. The pinout of the LTC3862 was carefully designed in order to make component placement easy. All of the power components can be placed on one side of the IC, away from all of the small-signal components. ...
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... MOSFET. If this ringing cannot be avoided and exceeds the maximum rating of the device, choose a higher voltage rated MOSFET or consider using a snubber. 16. When synchronizing the LTC3862 to an external clock, use a low impedance source such as a logic gate to drive the SYNC pin and keep the lead as short as possible. ...
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... LTC3862 TYPICAL APPLICATIONS A 12V Input, 24V/5A Output 2-Phase Boost Converter Application Circuit D MAX SLOPE BLANK PHASEMODE 45.3k FREQ 10nF SS 1nF LTC3862 26.7k ITH 100pF FB 6.98k SGND 130k V OUT CLKOUT SYNC PLLFLTR Start-Up RUN 5V/DIV I L1 5A/DIV I L2 5A/DIV V OUT 20V/DIV V = 12V 1ms/DIV 24V ...
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... I MASTER L2 5A/DIV I SLAVE L1 5A/DIV I SLAVE L2 5A/DIV V OUT 200mV/DIV 250μs/DIV 12V OUT LTC3862 L1 D1 2.7μH MBRB2515LT41 Q1 HAT2165H 0.005Ω 220μF 1W 16V + V + 33μF 10V OUT 12V 15A 33μF 10V 220μF 15μF 25V 16V 15μF 25V 0.005Ω ...
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... LTC3862 PACKAGE DESCRIPTION 6.60 0.10 4.50 0.10 RECOMMENDED SOLDER PAD LAYOUT (.169 – .177) 0.09 – 0.20 (.0035 – .0079) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE .254 MIN .0165 .0015 RECOMMENDED SOLDER PAD LAYOUT .0075 – .0098 (0.19 – 0.25) .016 – .050 (0.406 – 1.270) NOTE: 1 ...
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... UH Package 24-Lead Plastic QFN (5mm × 5mm) (Reference LTC DWG # 05-08-1747 Rev A) 0.75 0.05 PACKAGE OUTLINE 0.30 0.05 0.65 BSC R = 0.05 TYP 0.75 0.05 0.00 – 0.05 3.25 REF 0.200 REF LTC3862 PIN 1 NOTCH R = 0.30 TYP BOTTOM VIEW—EXPOSED PAD OR 0.35 45 CHAMFER R = 0.150 TYP 23 24 0.55 0. 3.20 0.10 3 ...
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