LT1945 LINER [Linear Technology], LT1945 Datasheet
LT1945
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LT1945 Summary of contents
Page 1
... DC/DC converter in a 10-pin MSOP package. Each converter is designed with a 350mA current limit and an input voltage range of 1.2V to 15V, making the LT1945 ideal for a wide variety of appli- cations. Both converters feature a quiescent current of only load, which further reduces to 0 shutdown ...
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... Switch Leakage Current Switch Off, V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1945 is guaranteed to meet performance specifications from Specifications over the – operating 2 U PACKAGE/ORDER I FOR ATIO ...
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... Input Supply Pin. Bypass this pin with a IN capacitor as close to the device as possible. SW1 (Pin 10): Switch Pin for Switcher 1. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to the pin to minimize EMI. LT1945 NFB1 Pin Voltage and Bias Current 50 –1.25 –1.24 ...
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... GND 3 (EXTERNAL) U OPERATIO The LT1945 uses a constant off-time control scheme to provide high efficiencies over a wide range of output current. Operation can be best understood by referring to the block diagram in Figure 1. Q1 and Q2 along with R3 and R4 form a bandgap reference used to regulate the output voltage. When the voltage at the NFB1 pin is slightly below – ...
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... Inductor Selection—Boost Regulator The formula below calculates the appropriate inductor value to be used for a boost regulator using the LT1945 (or at least provides a good starting point). This value pro- vides a good tradeoff in inductor size and system perfor- mance. Pick a standard inductor close to this value. A ...
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... Ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to the LT1945. A 4.7 F input capacitor is suffi- cient for most applications. Table 2 shows a list of several capacitor manufacturers. Consult the manufacturers for more detailed information and for their entire selection of related parts ...
Page 7
... To reduce the output ripple, increase the output capacitor value or add a 4.7pF feed-forward capaci- tor in the feedback network of the LT1945 (see the circuits in the Typical Applications section). Adding this small, inexpensive 4.7pF capacitor will greatly reduce the output voltage ripple ...
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... LT1945 U TYPICAL APPLICATIO Dual Output ( 32V) Converter SW1 SHDN1 NFB1 C1 LT1945 D2 4 SHDN2 FB2 GND PGND PGND SW2 4.7pF C1: TAIYO YUDEN JMK212BJ475 (408)573-4150 (408)573-4150 C2, C3: TAIYO YUDEN GMK316BJ105 C4: TAIYO YUDEN UMK212BJ104 ...