LTC1872 Linear Technology, LTC1872 Datasheet
LTC1872
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LTC1872 Summary of contents
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... FB 422k C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT C2: MURATA GRM42-2X5R226K6.3 D1: IR10BQ015 L1: MURATA LQN6C4R7M04 M1: IRLMS2002 R1: DALE 0.25W Figure 1. LTC1872 High Output Current 3. Boost Converter Constant Frequency Current Mode Step-Up DC/DC Controller in SOT-23 DESCRIPTIO ® The LTC 1872 is a constant frequency current mode step- up DC/DC controller providing excellent AC and DC load and line regulation ...
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... LOAD (Note 6) Note 4: Dynamic supply current is higher due to the gate charge being delivered at the switching frequency. Note 5: The LTC1872 is tested in a feedback loop that servos V output of the error amplifier. Note 6: Guaranteed by design at duty cycle = 30%. Peak current sense voltage is V and power increases due to slope compensation as shown in Figure 2 ...
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... G04 – SENSE (Pin 4): The Negative Input to the Current Com- parator. V (Pin 5): Supply Pin. Must be closely decoupled to GND IN Pin 2. NGATE (Pin 6): Gate Drive for the External N-Channel MOSFET. This pin swings from LTC1872 Undervoltage Lockout Trip Voltage vs Temperature 2.24 V FALLING IN 2.20 2.16 2.12 2.08 2 ...
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... U OPERATIO (Refer to Functional Diagram) Main Control Loop The LTC1872 is a constant frequency current mode switch- ing regulator. During normal operation, the external N-channel power MOSFET is turned on each cycle by the oscillator and turned off when the current comparator (ICMP) resets the RS latch. The peak inductor current at ...
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... The inductor’s peak current is determined by: V ITH when the LTC1872 is operating below 40% duty cycle. However, once the duty cycle exceeds 40%, slope com- pensation begins and effectively reduces the peak induc- tor current. The amount of reduction is given by the curves in Figure 2. Short-Circuit Protection ...
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... SENSE With the current comparator monitoring the voltage devel- oped across R , the threshold of the comparator SENSE determines the inductor’s peak current. The output cur- rent the LTC1872 can provide is given by RIPPLE I OUT ...
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... MOSFET (R guaranteed 2.5V) is required for applications that GS work close to this voltage. When these MOSFETs are used, make sure that the input supply to the LTC1872 is less than the absolute maximum V rating, typically 8V. GS The required minimum R of the MOSFET is gov- ...
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... U is the output Setting Output Voltage OUT The LTC1872 develops a 0.8V reference voltage between the feedback (Pin 3) terminal and ground (see Figure 4). By selecting resistor R1, a constant current is caused to flow through R1 and R2 to set the overall output voltage. The regulated output voltage is determined by: ...
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... Although all dissipative elements in the circuit produce losses, four main sources usually account for most of the losses in LTC1872 circuits: 1) LTC1872 DC bias current, 2) MOSFET gate charge current voltage drop of the output diode. 1. The V ...
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... V IN (Pin 2). R ITH C ITH BOLD LINES INDICATE HIGH CURRENT PATHS Figure 5. LTC1872 Layout Diagram (See PC Board Layout Checklist Connect the end of R possible. The V comparator. 5. The trace from SENSE should be kept short. The trace should connect close ...
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... L1 I /RUN LTC1872 2 4 – GND SENSE + NGATE M1 FB 1.1M 78.7k L1: COILTRONICS UP2B-100 M1: Si9804DV R1: DALE 0.25W LTC1872 Three-Cell White LED Driver R1 0. /RUN 150 H LTC1872 2 4 – GND SENSE + NGATE M1 FB L1: COILCRAFT DO1608C-154 M1: Si9804 R1: DALE 0 ...
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... LTC1872 U TYPICAL APPLICATIO LTC1872 – 2.5V to 3.3V/0.5A Boost Converter /RUN LTC1872 10k 2 4 – GND SENSE 3 6 220pF V NGATE 0.1 F 100 F CERAMIC 10V V IN –2.5V C1, C2: AVX TPSE107M010R0100 M1: Si9804DV D1: MOTOROLA MBR2045CT R1: DALE 0.25W L1: COILTRONICS UP2B-4R7 U1: PANASONIC 2SB709A PACKAGE DESCRIPTION 2.6 – 3.0 (0.110 – 0.118) 1.50 – ...