Electronic Components Datasheet Search |
|
LTC1574CS Datasheet(PDF) 4 Page - Linear Technology |
|
LTC1574CS Datasheet(HTML) 4 Page - Linear Technology |
4 / 8 page 4 LTC1574 LTC1574-3.3/LTC1574-5 PIN FUNCTIONS VOUT or VFB (Pin 10): For the LTC1574, this pin connects to the main voltage comparator input. On the LTC1574-5 and LTC1574-3.3, this pin goes to an internal resistive divider which sets the output voltage. LBOUT (Pin 11): Open drain of an N-Channel Pull-Down. This pin will sink current when (Pin 12) LBIN goes below 1.25V. LBIN (Pin 12): The (–) Input of the Low-Battery Voltage Comparator. The (+) input is connected to a reference voltage of 1.25V. NC (Pins 1, 8, 9, 16): No Connection. GND (Pins 2, 4, 13, 15): Ground. SW (Pins 3, 14): Drain of P-Channel MOSFET Switch and Cathode of Schottky Diode. VIN (Pin 5): Input Supply Voltage. It must be decoupled close to ground (Pin 4). IPGM (Pin 6): This pin selects the current limit of the P-channel switch. With IPGM = VIN, the current trip point is 600mA and with IPGM = 0V, the current trip point is reduced to 340mA. SHDN (Pin 7): Pulling this pin to ground keeps the internal switch off and puts the LTC1574 in micropower shutdown. APPLICATIONS INFORMATION Operating Frequency and Inductor Since the LTC1574 utilizes a constant off-time architecture, its operating frequency is dependent on the value of VIN. The frequency of operation can be expressed as: f t VV VV Hz OFF IN OUT IN D = − + () 1 where tOFF = 4µs and VD is the voltage drop across the internal Schottky diode. Note that the operating frequency is a function of the input and output voltage. Although the size of the inductor does not affect the fre- quency or inductor peak current, it does affect the ripple current. The peak-to-peak ripple current is given by: I VV L RIPPLE OUT D =× + () − 410 6 AP-P By choosing a smaller inductor, a low ESR (Effective Series Resistance) output filter capacitor has to be used. Core loss will increase due to higher ripple current. Short-Circuit Protection The LTC1574 is protected from output short circuits by its internal current limit. Depending on the condition of the Low-Battery Detector The low-battery indicator senses the input voltage through an external resistive divider. This divided voltage connects to the “–” input of a voltage comparator (Pin 12) which is compared with a 1.25V reference voltage. With the current IPGM pin, the limit is either set to 340mA or 600mA. In addition, the off-time of the switch is increased to allow the inductor current to decay far enough to prevent any current build-up (see Figure 1). IPGM = VIN IPGM = 0 GND L = 100 µH VIN = 13.5V 20 µs/DIV 1574 • F01 Figure 1. Inductor Current with Output Shorted |
Similar Part No. - LTC1574CS |
|
Similar Description - LTC1574CS |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |