LTC3836 LINER [Linear Technology], LTC3836 Datasheet
LTC3836
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LTC3836 Summary of contents
Page 1
... The LTC3836 features an internal 1ms soft-start that can be extended with an external capacitor. A tracking input al- lows the second output to track the fi rst during start-up. The LTC3836 is available in the tiny thermally enhanced (4mm × 5mm) QFN and 28-lead narrow SSOP packages. SENSE ...
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... TAPE AND REEL LTC3836EGN#PBF LTC3836EGN#TRPBF LTC3836EUFD#PBF LTC3836EUFD#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi ...
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... D Note 4: Dynamic supply current is higher due to gate charge being delivered at the switching frequency. Note 5: The LTC3836 is tested in a feedback loop that servos I specifi ed voltage and measures the resultant V Note 6: Peak current sense voltage is reduced dependent on duty cycle to a percentage of value as shown in Figure 1. ...
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... LTC3836 TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency vs Load Current 100 90 80 PULSE-SKIPPING 70 MODE 60 FORCED 50 CONTINUOUS MODE 40 30 SYNC/FCB = V SYNC/FCB = 100 1000 LOAD CURRENT (mA 3.3V IN 3836 G01 V = 1.5V OUT CIRCUIT OF FIGURE 15 Light Load (Pulse-Skipping Mode 2V/DIV V OUT 20mV/DIV AC COUPLED INDUCTOR CURRENT ...
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... TEMPERATURE (°C) Shutdown Quiescent Current vs Input Voltage 2.5 3.0 3.5 4.0 100 INPUT VOLTAGE (V) LTC3836 T = 25°C unless otherwise noted. A Shutdown (RUN/SS) Threshold vs Temperature 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 –60 –40 – 100 TEMPERATURE (°C) 3836 G11 ...
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... A capacitor to ground at this pin sets the ramp time to fi nal regulated output voltage. Alternatively, a resistor divider on another voltage supply connected to this pin allows the LTC3836 output to track the other supply dur- ing start-up. PGOOD (Pin 13)/(Pin 10): Power-Good Output Voltage Monitor Open-Drain Logic Output. This pin is pulled to ...
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... VIN VOLTAGE 0.6V REFERENCE V REF SHDN + t = 1ms SEC EXTSS – PHASE DETECTOR CLK1 VOLTAGE SLOPE CLK2 COMP – V FB1 FCB FCB + 0.54V + – V FB2 LTC3836 + /SENSE2 (Pins 28, 5)/(Pins 25, 12): Positive INTSS SLOPE1 SLOPE2 UV1 PGOOD OV1 SHDN 37362 FD OV2 UV2 3836fa 7 ...
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... LTC3836 FUNCTIONAL DIAGRAM CLK1 – ICMP + IPRG1 OV1 8 (Controller 1) RS1 SWITCHING LOGIC ANTISHOOT AND THROUGH OV1 BLANKING SC1 CIRCUIT FCB IREV1 SLOPE1 SW1 + SENSE1 SHDN + EAMP – SC1 SCP + V FB1 OVP IREV1 RICMP – 0.68V IPROG1 BOOST1 SENSE1 C CB ...
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... THROUGH OV2 BLANKING CIRCUIT SC2 FCB IREV2 SLOPE2 SW2 + SENSE2 SHDN + EAMP – SC2 SCP TRACK + V FB2 OVP IREV2 – 0.68V FCB LTC3836 BOOST2 SENSE2 TG2 PGND SW2 L2 V OUT2 BOOST2 C BG2 OUT2 PGND – R2B V FB2 + 0.60V R2A ...
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... MOSFETs are held off. Light Load Operation (Pulse-Skipping or Continuous Conduction) (SYNC/FCB Pin) The LTC3836 can be enabled to enter high effi ciency pulse- skipping operation or forced continuous conduction mode at low load currents. To select pulse-skipping operation, tie the SYNC/FCB pin voltage above 0.6V (e.g., V ...
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... SYNC/FCB pin. In this case, a series RC should be connected between the PLLLPF pin and SGND to serve as the PLL’s loop fi lter. The LTC3836 phase detector adjusts the voltage on the PLLLPF pin to < 0.12V), the FB align the turn-on of controller 1’ ...
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... Undervoltage Lockout To prevent operation of the external MOSFETs below safe input voltage levels, an undervoltage lockout is incorpo- rated in the LTC3836. When the input supply voltage (V drops below 2.25V, the external MOSFETs and all internal circuitry are turned off except for the undervoltage block, which draws only a few microamperes ...
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... OPERATION (Refer to Functional Diagram) Figure 2 shows example waveforms for a single phase dual controller versus a 2-phase LTC3836 system. In this case, two outputs of different voltage, each drawing the same load current are derived from a single input supply. In this example, 2-phase operation could halve the RMS input capacitor current ...
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... DS(ON) t and the total gate charge Q D(OFF) G The gate drive voltage is the input supply voltage. Since the LTC3836 is designed for operation down to low input voltages, a sublogic level MOSFET ( 2.5V) is required for applications that work close GS to this voltage. The main MOSFET’s on-resistance is chosen based on the required load current ...
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... SYNC/FCB pin low or high. Pulling the PLLLPF to V pulling the PLLLPF to GND selects 300kHz operation. Alternatively, the LTC3836 will phase-lock to a clock signal applied to the SYNC/FCB pin with a frequency between 250kHz and 850kHz (see Phase-Locked Loop and Fre- quency Synchronization) ...
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... Always consult the manufacturer IN if there is any question. The benefi the LTC3836 2-phase operation can be cal- culated by using the equation above for the higher power controller and then calculating the loss that would have resulted if both controller channels switched on at the same time ...
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... APPLICATIONS INFORMATION A small (0.1μF to 1μF) bypass capacitor between the chip V pin and ground, placed close to the LTC3836, is also IN suggested. A 10Ω resistor placed between C the V pin provides further isolation between the two IN channels. The selection driven by the effective series OUT resistance (ESR) ...
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... TRACK/SS2 pin. Normally this pin is used to allow the start track that shown qualitatively OUT2 OUT1 in Figures 7a and 7b. When the voltage on the TRACK/SS2 pin is less than the internal 0.6V reference, the LTC3836 TIME (7b) Coincident Tracking Figures 7b and 7c. Two Different Modes of Output Voltage Tracking 18 is controlled by regulates the V OUT1 instead of 0 ...
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... FCB, is shown in Figure 8 and specifi the Electrical Characteristics table. Note that the LTC3836 can only be synchronized to an external clock whose frequency is within range of the LTC3836’s internal VCO, which is nominally 200kHz to 1MHz. This is guaranteed, over temperature and variations between 300kHz and 750kHz. A simplifi ...
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... Current Reversal Allowed Pulse-Skipping Operation Enabled No Current Reversal Allowed Enable Phase-Locked Loop (Synchronize to External CLK) Pulse-Skipping at Light Loads No Current Reversal Allowed and D between the output and the I FB1 FB2 V OUT 1/2 LTC3836 FB1 FB2 3836 F11 Figure 11. Foldback Current Limiting ...
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... However the sense resistor causes extra losses in addition to those of the MOSFET. Therefore, using a sense resistor lowers the effi ciency of LTC3836, especially at high load currents. Low Supply Operation Although the LTC3836 can function down to below 2.4V, the maximum allowable output current is reduced as V decreases below 3V ...
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... L1, L2, etc. are the individual losses as a percent- age of input power. Although all dissipative elements in the circuit produce losses, fi ve main sources usually account for most of the losses in LTC3836 circuits: 1) LTC3836 DC bias cur- rent, 2) MOSFET gate charge current transition losses. 1) The V ...
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... PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3836. These items are illustrated in the layout diagram of Figure 13. Figure 14 depicts the current waveforms present in the various branches of the 2-phase dual regulator. ...
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... L1, L2: VISHAY IHLP2525CZERR 47M01 C : 22μF X2, 6.3V, X5R TAIYO YUDEN JMK235BJ107MM X2 OUT1 OUT2 M1-M4: VISHAY Si7882DP Figure 15. 2-Phase, 550kHz, Dual Output Synchronous DC/DC Converter with Ceramic Output Capacitors Figure 14. Branch Current Waveforms D LTC3836EUFD R , 59k 1 FB1A 24 V BOOST1 FB1 R , 11.8k TRACKA 26 7 SW1 TRACK/SS2 , 82pF 25 + ...
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... BG2 TG2 10Ω 10 VIN PGOOD SENSE2 IPRG2 SW2 TH2 , 64.9k ITH2 13 BOOST2 N/C N/C FB2 16 28 10000 3836 F16b LTC3836 C , 82pF FFW1 R , 88.7k, 1% FB1B C , 0.22μ 0.22μ FB2B 49.9k, 1% 3836 F16 C , 82pF FFW2 V OUT 200mV/DIV AC COUPLED I ...
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... Figure 17a. Single Output, High Current Application with External Frequency Synchronization 100 100 1000 LOAD CURRENT (mA) Figure 17b. Effi ciency vs Load Current 26 LTC3836EUFD R , 61.9k FB1A BOOST1 FB1 , 61.9k TRACKA 26 7 SW1 TRACK/SS2 25 + SENSE1 , 1.37k TG1 TH1 22 ...
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... DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE LTC3836 .386 – .393* .033 (9.804 – 9.982) (0.838) ...
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... LTC3836 RELATED PARTS PART NUMBER DESCRIPTION LTC1735 High Effi ciency Synchronous Step-Down Controller TM LTC1778 No R Synchronous Step-Down Controller SENSE LTC2923 Power Supply Tracking Controller LTC3411 1.25A (I ), 4MHz, Synchronous Step-Down DC/DC Converter 95% Effi ciency, V OUT LTC3412A 4MHz, Synchronous Step-Down DC/DC Converter OUT ...