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LTC1174CS8-5 Datasheet(PDF) 9 Page - Linear Technology |
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LTC1174CS8-5 Datasheet(HTML) 9 Page - Linear Technology |
9 / 16 page 9 LTC1174 LTC1174-3.3/LTC1174-5 S APPLICATI I FOR ATIO Figure 3. Low-Battery Comparator LTC1174 – + 1.25V REFERENCE R4 R3 3 VIN 1174 F03 LTC1174 Adjustable Applications The LTC1174 develops a 1.25V reference voltage between the feedback (pin 1) 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: V R R OUT =+ 125 1 2 1 . For most applications, a 30k resistor is suggested for R1. To prevent stray pickup, a 100pF capacitor is suggested across R1 located close to the LTC1174. Figure 4. LTC1174 Adjustable Configuration LTC1174 VFB R2 R1 1 VOUT 1174 F04 100pF Inverting Applications The LTC1174 can easily be set up for a negative output voltage. If – 5V is desired, the LTC1174-5 is ideal for this application as it requires the least components. Figure 5 shows the schematic for this application. Note that the output voltage is now taken off the GND pin. Therefore, the maximum input voltage is now determined by the difference between the absolute maximum voltage rating and the output voltage. A maximum of 12V is specified in + + 3 LTC1174HV-5 LBIN LBOUT IPGM GND VIN SHUTDOWN VOUT SW 2 7 6 8 1 5 4 50 µH** VOUT –5V 45mA 2 × 47µF* 16V MBRS140T3 1174 F05 * ** AVX TPSD476K016 COILTRONICS CTX50-4 INPUT VOLTAGE 4V TO 12V 0.1 µF + 2 × 47µF* 16V Figure 5. Positive-to-Negative 5V Converter Figure 5, giving the circuit a 1.5V of headroom for VIN. Note that the circuit can operate from a minimum of 4V, making it ideal for a 4 NiCad cell application. For a higher output current circuit, please refer to the Typical Applica- tions section. Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC1174. These items are also illustrated graphically in the layout diagram in Figure 6. Check the following in your layout: 1. Is the Schottky catch diode closely connected between ground (pin 4) and switch (pin 5)? 2. Is the “+” plate of CIN closely connected to VIN (pin 6)? This capacitor provides the AC current to the internal P-channel MOSFET. 3. Is the 0.1 µF VIN decoupling capacitor closely conected between VIN (pin 6) and ground (pin 4)? This capacitor carries the high frequency peak currents. 4. Is the SHUTDOWN (pin 8) actively pulled to VIN during normal operation? The SHUTDOWN pin is high imped- ance and must not be allowed to float. 5. Is the IPGM (pin 7) pulled either to VIN or ground? The IPGM pin is high impedance and must not be allowed to float. |
Similar Part No. - LTC1174CS8-5 |
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Similar Description - LTC1174CS8-5 |
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