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X80203 Datasheet(PDF) 8 Page - Intersil Corporation |
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X80203 Datasheet(HTML) 8 Page - Intersil Corporation |
8 / 16 page 8 FN8154.0 The READY output pin reflects the condition of the VDDH input. READY is LOW as long as VDDH is below UVLOH and remains LOW for a period of tPURST after VDDH crosses UVLOH, see Figure 4. Once VDDH rises above UVLOH and remains stable for tPURST, the READY output turns ON. If READY connects directly to the GATEH_EN pin, then the GATE_H charge pump turns on immediately. The turn on of the Gate_H charge pump can be delayed by using an external filter (RC filter) connected between the READY and GATEH_EN pins. When VDDH drops below the UVLOH threshold, READY goes inactive immediately. For more details on this turn-off mechanism, See "Power Supply Failure Conditions" on page 9. SECONDARY VOLTAGES VDDM AND VDDL The VDDM and VDDL voltage inputs each have their own undervoltage lockout settings, UVLOM, and UVLOL, respectively. Each undervoltage lockout level is preset at the factory. For information on these settings, See Ordering Information. For custom programmed levels, contact Intersil. The GATE_M and GATE_ L charge pumps are OFF as long as VDDM, and VDDL are below their respective UVLO trip points. When READY is active and VDDM and VDDL go above their UVLO thresholds, the GATE_M and GATE_L charge pumps can be turned ON when activated as part of the power sequence desired. If VDDL or VDDM drop below the UVLO level the charge pumps turn off. For more details on this turn-off mechanism, See "Power Supply Failure Conditions" on page 9. Sequence Delay Logic. This block contains the logic circuits that implement the power-up and power-down sequencing of the VDDH (GATE_H), VDDM (GATE_M), and VDDL (GATE_L) voltages. The sequencing protocol has a built-in “core-first-up and core-down-last” algorithm. On power-up the GATE_L signal turns on first, followed by GATE_M signal. During the power-down, the GATE_M turns off first and the GATE_L signal follows. The sequencing of the power supplies is primarily controlled and regulated via the SETV and the ENS (enable sequence) pins. All charge pumps are designed to ramp up their respective gates at the same slew rate for the same load. Time Based Power Sequencing (ENS option) The ENS (Enable Sequence) pin controls the start of the ramp up/ramp down sequence for GATE_M and GATE_L in the time domain. (See Figure 3.) ENS is an edge-triggered input. A rising edge (LOW to HIGH) on the ENS input turns on the charge pump that drives the GATE_L output. The slew rate of the GATE_L output depends on the external MOSFET and any load connected to it. (See Electrical Table). After a tDELAY_UP time, the GATE_M charge pump turns ON. Again the slew rate is dependent on the load connected to GATE_M output. The falling edge transition on the ENS pin (HIGH to LOW) turns off the charge pump that drives the GATE_M output. After a tDELAY_DOWN time period, the GATE_L charge pump turns OFF. Voltage Based Power Sequencing (SETV Option) Using the SETV pin allows for a voltage based sequencing of the GATE_L and GATE_M outputs. SETV is an edge triggered input signal. A LOW to HIGH transition on SETV immediately turns ON the charge pump for GATE_L. The GATE_L output then starts ramping up. In this configuration, the drain of the MOSFET “L” connects to the VFB pin and this voltage is compared to an external reference applied to the REF pin. The comparator turns on the charge pump for GATE_M once the voltage on VFB exceeds the voltage on REF. (See Figure 5.) The voltage sequencing comparator has a 30mV hysteresis, so the GATE_M output does not oscillate as the core voltage powers up. A High to Low transition of SETV turns OFF charge pump M and GATE_M is pulled low. After a tDELAY_DOWN time period, charge pump L turns off and GATE_L is pulled low. tDELAY_UP ENS GATE_L GATE_M tDELAY_DOWN FIGURE 3. TIME BASED SEQUENCING OF GATE_M AND GATE_L tPURST UVLOH VDDH READY FIGURE 4. VDDH/READY SEQUENCING X80200, X80201, X80202, X80203, X80204 |
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