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SIC789 Datasheet(PDF) 5 Page - Vishay Siliconix |
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SIC789 Datasheet(HTML) 5 Page - Vishay Siliconix |
5 / 19 page SiC789, SiC789A www.vishay.com Vishay Siliconix S14-2287-Rev. B, 08-Dec-14 5 Document Number: 62972 For technical questions, contact: powerictechsupport@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Notes (1) Typical limits are established by characterization and are not production tested. (2) Guaranteed by design. DETAILED OPERATIONAL DESCRIPTION PWM Input with Tri-state Function The PWM input receives the PWM control signal from the VR controller IC. The PWM input is designed to be compatible with standard controllers using two state logic (H and L) and advanced controllers that incorporate tri-state logic (H, L and tri-state) on the PWM output. For two state logic, the PWM input operates as follows. When PWM is driven above VPWM_TH_R the low-side is turned OFF and the high-side is turned ON. When PWM input is driven below VPWM_TH_F the high-side is turned OFF and the low-side is turned ON. For tri-state logic, the PWM input operates as previously stated for driving the MOSFETs when PWM is logic high and logic low. However, there is a third state that is entered as the PWM output of tri-state compatible controller enters its high impedance state during shut-down. The high impedance state of the controller’s PWM output allows the SiC789 and SiC789A to pull the PWM input into the tri-state region (see definition of PWM logic and Tri-State, fig. 4). If the PWM input stays in this region for the Tri-state Hold-Off Period, tTSHO, both high-side and low-side MOSFETs are turned OFF. The function allows the VR phase to be disabled without negative output voltage swing caused by inductor ringing and saves a Schottky diode clamp. The PWM and tri-state regions are separated by hysteresis to prevent false triggering. The SiC789A incorporates PWM voltage thresholds that are compatible with 3.3 V logic and the SiC789 thresholds are compatible with 5 V logic. Disable (DSBL#) In the low state, the DSBL# pin shuts down the driver IC and disables both high-side and low-side MOSFETs. In this state, standby current is minimized. If DSBL# is left unconnected, an internal pull-down resistor will pull the pin to CGND and shut down the IC. Pre-Charger Function When DSBL# is driven from below VIL_DSBL# to above VIH_DSBL# the low-side is turned ON for a short duration (60 ns typical) to refresh the BOOT capacitor in case it has been discharged due to the driver being in standby for a long period of time. Diode Emulation Mode (SMOD#) When SMOD# is logic low diode emulation mode is enabled and the low-side is turned OFF. This is a non-synchronous conversion mode that improves light load efficiency by reducing switching losses. Conducted losses that occur in synchronous buck regulators when inductor current is negative can also be reduced. Circuitry in the external controller IC detects when inductor current crosses zero and drives SMOD# below VIL_SMOD# turning the low-side MOSFET OFF. The function can be also be used for a pre-biased output voltage. If SMOD# is left unconnected, an internal pull up resistor will pull the pin to VCIN (logic high) to disable the SMOD# function. Thermal Shutdown Warning (THWn) The THWn pin is an open drain signal that flags the presence of excessive junction temperature. Connect, with a maximum of 20 k Ω, to VCIN. An internal temperature sensor detects the junction temperature. The temperature threshold is 160 °C. When this junction temperature is exceeded the THWn flag is set. When the junction temperature drops below 135 °C the device will clear the THWn signal. The SiC789 and SiC789A do not stop operation when the flag is set. The decision to shutdown must be made by an external thermal control function. DSBL# SMOD# INPUT DSBL# Logic Input Voltage VIH_DSBL# Input logic high 2 - - V VIL_DSBL# Input logic low - - 0.8 SMOD# Logic Input Voltage VIH_SMOD# Input logic high 2 - - VIL_SMOD# Input logic low - - 0.8 PROTECTION Under Voltage Lockout VUVLO VCIN rising, on threshold - 3.7 4.1 V VCIN falling, off threshold 2.7 3.1 - Under Voltage Lockout Hysteresis VUVLO_HYST - 575 - mV THWn Flag Set (2) TTHWn_SET - 160 - °C THWn Flag Clear (2) TTHWn_CLEAR - 135 - THWn Flag Hysteresis (2) TTHWn_HYST -25- THWn Output Low VOL_THWn ITHWn = 2 mA - 0.02 - V ELECTRICAL SPECIFICATIONS (DSBL# = SMOD# = 5 V, VIN = 12 V, VDRV and VCIN = 5 V, TA = 25 °C) PARAMETER SYMBOL TEST CONDITION LIMITS UNIT MIN. TYP. MAX. |
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