Electronic Components Datasheet Search |
|
ISL6174IRZ Datasheet(PDF) 11 Page - Intersil Corporation |
|
ISL6174IRZ Datasheet(HTML) 11 Page - Intersil Corporation |
11 / 16 page 11 FN6830.0 December 19, 2008 Current Set Resistor (RSET) This resistor sets the threshold for the Circuit Breaker comparator in conjunction with RSNS. Once RSNS has been selected, use Equation 1 to calculate RSET. Use 20µA for ISET in a typical application. Reference Current Set Resistor (RREF) This resistor sets up the current in the internal current source, IREF/4, shown in Figure 2 for the comparators. The voltage at the OCREF pin is the same as the internal bandgap reference. The current (IREF) flowing through this resistor is simply: IREF = 1.178/RREF This current, IREF, should be set at 80µA to force 20µA in the internal current source as shown in Figure 2, because of the 4:1 current mirror. This equates to the resistor value of 14.7k. Selection of Rs1 and Rs2 These resistors set the UV detect point. The UV comparator detects the undervoltage condition when it sees the voltage at UV pin drop below 0.633V. The resistor divider values should be selected accordingly. Charge Pump Capacitor Selection (CP and CV) CP is the “flying cap” and CV is the smoothing cap of the charge pump, which operates at 450kHz set internally. The output resistance of the charge pump, which affects the regulation, is dependent on the CP value and its ESR, charge-pump switch resistance, and the frequency and ESR of the smoothing cap, CV. It is recommended that CP be kept within 0.022µF (minimum) to 0.1µF (maximum) range. Only ceramic capacitors are recommended. Use 0.1µF cap if CPVDD output is expected to power an external circuit, in which case the current draw from CPVDD must be kept below 10mA. CV should at least be 0.47µF (ceramic only). Higher values may be used if low ripple performance is desired. Time-out Capacitor Selection (CT) This capacitor determines the current regulation delay period. As shown in Figure 2, when the voltage across this capacitor exceeds 1.178V, the time-out comparator detects it and the gate voltage is pulled to 0V thus shutting down the channel. An internal 10µA current source charges this capacitor. Hence, the value of this capacitor is determined by Equation 2. Where, TOUT = Desired time-out period. Soft-Start Capacitor Selection (CSS) The rate of change of voltage (dv/dt) on this capacitor, which is determined by the internal 10µA current source, is the same as that on the output load capacitance. Hence, the value of this capacitor directly controls the inrush current amplitude during hot swap operation. Where, CO = Load Capacitance IINRUSH = Desired Inrush Current IINRUSH is the sum of the DC steady-state load current and the load capacitance charging current. If the DC steady-state load remains disabled until after the soft-start period expires (PGx could be used as a load enable signal, for example), then only the capacitor charging current should be used as IINRUSH. The Css value should always be more than (1/2.4) of that of Ciss of the MOSFET to ensure proper soft-start operation. This is because the Ciss is charged from 24µA current source, whereas the Css gets charged from a 10µA current source (Figure 15). In order to make sure both VSS and VO track during the soft-start, this condition is necessary. ISL6174 Evaluation Platform The ISL617XEVAL1Z is the primary evaluation board for this IC. For the BOM, schematic and photograph, see the “BOM for ISL617XEVAL1Z Board and Schematic” on page 15. The evaluation board has been designed with a typical application in mind and with accessibility to all the featured pins to enable a user to understand and verify these features of the IC. The two circuit breaker levels are programmed to 2.2A for each input rail but they can easily be scaled up or down by adjusting some component values. There are two input voltages, one for each channel that are switched by a dual N-Channel MOSFET (Q1) to the output connectors. LOAD CURRENT CARRYING TRACES RSNS CURRENT SENSE TRACES FIGURE 17. RECOMMENDED CURRENT SENSE RESISTOR PCB LAYOUT C T 10 μAT OUT • () 1.178 ⁄ = (EQ. 2) C SS C O 10 μAI INRUSH ⁄ () • = (EQ. 3) ISL6174 |
Similar Part No. - ISL6174IRZ |
|
Similar Description - ISL6174IRZ |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |