L6995D

L6995 STEP DOWN CONTROLLER FOR HIGH DIFFERENTIAL INPUT-OUTPUT CONVERSION FEATURE s CONSTANT ON TIME TOPOLOGY ALLOWS OPERATION WITH LOWER DUTY THAN PWM TOPOLOGY s VERY FAST LOAD TRANSIENTS s 5V Vcc SUPPLY s 1.5V TO 28V INPUT VOLTAGE RANGE s 0.9V ±1% VREF s MINIMUM OUTPUT VOLTAGE AS LOW AS 0.9V s SELECTABLE SINKING MODE s LOSSLESS CURRENT LIMIT s REMOTE SENSING s OVP,UVP LATCHED PROTECTIONS s 600 µA TYP QUIESCENT CURRENT s POWER GOOD AND OVP SIGNALS s PULSE SKIPPING AT LIGHT LOADS APPLICATIONS s I/O BUS FOR CPU CORE SUPPLY s NOTEBOOK COMPUTERS s NETWORKING DC-DC s DISTRIBUTED POWER TSSOP20 ORDERING NUMBERS: L6995D L6995DTR DESCRIPTION The device is a step-down controller specifically designed to provide extremely high efficiency conversion, with losses current sensing tecnique. The "constant on-time" topology assures fast load transient response. The embedded "voltage feed-forward" provides nearly constant switching frequency operation. An integrator can be introduced in the control loop to reduce the static output voltage error. The available remote sensing improve the static and dynamic regulation recovering the wires voltage drop. Pulse skipping technique reduces power consumption at light load. Drivers current capability allows output current in excess of 20A. 28V MINIMUM COMPONENT COUNT APPLICATION Rin2 Rin1 5V CIN SHDN VCC VDR OSC BOOT HGATE 5V C HS D BOOT BOOT Vo L PHASE LGATE RILIM ILIM PGND LS 0.9V COUT DS L6995 SS GND NOSKIP VSENSE CSS INT VFB VREF CVREF December 2002 This is preliminary information on a new product now in development. Details are subject to change without notice. 1/25 L6995 ABSOLUTE MAXIMUM RATINGS Symbol VCC VDR VCC to GND VDR to GND HGATE and BOOT, to PHASE HGATE and BOOT, to PGND VPHASE PHASE LGATE to PGND ILIM, VFB, VSENSE, NOSKIP, SHDN, PGOOD, OVP, VREF, INT, GNDSENSE to GND Ptot Tstg Power dissipation at Tamb = 25°C Storage temperature range Parameter Value -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 36 -0.3-to 30 -0.3 to VDR+0.3 -0.3 to VCC+0.3 1 -40 to 150 Unit V V V V V V V W °C THERMAL DATA Symbol Rth j-amb Tj Parameter Thermal Resistance Junction to Ambient Junction operating temperature range Value 125 0 to 125 Unit °C/W °C PIN CONNECTION (Top View) NOSKIP GNDSENSE INT VSENSE VCC GND VREF VFB OSC SS 1 2 3 4 5 6 7 8 9 10 TSSOP20 20 19 18 17 16 15 14 13 12 11 BOOT HGATE PHASE VDR LGATE PGND PGOOD OVP SHDN ILIM PIN FUNCTION N° 1 2 3 4 5 6 7 Name NOSKIP GNDSE NSE INT VSENS E VCC GND VREF Remote ground sensing pin Integrator output. Short this pin to VFB pin and connect it via a capacitor to VOUT to insert the integrator in the control loop. If the integrator is not used, short this pin to VREF. This pin must be connected to the remote output voltage to detect overvoltage and undervoltage conditions and to provide integrator feedback input. Supply voltage for IC core. Connect to 5V bus. Signal ground 0.9 V voltage reference. Connect max. a 10nF ceramic capacitor between this pin and ground. This pin is capable to source or sink up to 250uA Description Connect to VCC to force continuous conduction mode and sink mode. 2/25 L6995 PIN FUNCTION (continued) N° 8 9 10 11 12 13 14 15 16 17 18 19 20 Name VFB OSC SS ILIM SHDN OVP PGOOD PGND LGATE VDR PHASE HGATE BOOT Description PWM comparator feedback input. Short this pin to INT pin when using the integrator function, or to VSENSE pin without integrator. Connect this pin to the input voltage through a voltage divider in order to provide the feedforward function. It cannot be left floating. Soft start pin. A 5µA constant current charges an external capacitor which value sets the softstart time. An external resistor connected between this pin and GND sets the current limit threshold. Shutdown. When shorted to GND the device stops working; when high, it enables the normal operation. It cannot be left floating. Open drain output. When in OVP condition, the internal transistor goes off. Connect this pin to VCC through a resistor. Open drain output. The internal transistor is on during soft-start or in case of output voltage faults. Connect this pin to VCC through a resistor. Low Side driver ground. Low Side driver output. Low Side driver supply. Return path of the High Side driver. High side MOSFETS driver output. Bootstrap capacitor pin. High Side driver is supplied through this pin. ELECTRICAL CHARACTERISTICS (VCC = VDR = 5V; Tamb = 0°C to 85°C unless otherwise specified) Symbol SUPPLY SECTION Vin VCC, VDR VCC Iqcc (VDR) Iqcc (Vcc) SHDN ISH (VDR) ISH (VCC) ISS ON TIME Ton On time duration VREF=VSENSE OSC=250mV 850 950 1050 ns Turn-onvoltage Turn-off voltage Driver quiescent current Quiescent current VFB > VREF VFB > VREF Input voltage range Vout=Vref Fsw=110Khz Iout=1A 1.5 4.5 4.2 4.1 28 5.5 4.4 4.3 20 600 V V V V µA µA Parameter Test Condition Min. Typ. Max. Unit SHUTDOWN SECTION Device On Device Off Driver quiescent current in shutdown Shut down current SHDN to GND SHDN to GND 1.2 0.6 5 15 V V µA µA SOFT START SECTION Soft Start current SS Clamp Voltage 4 4 6 µA V 3/25 L6995 ELECTRICAL CHARACTERISTICS (continued) (VCC = VDR = 5V; Tamb = 0°C to 85°C unless otherwise specified) Symbol Parameter Test Condition VREF=VSENSE OSC=500mV VREF=VSENSE OSC=1V VREF=VSENSE OSC=2V OFF TIME TOFFMIN Minimum off time KOSC/TOFFMIN VOLTAGE REFERENCE VREF Voltage Accuracy Input voltage offset IFB Input Bias Current ILIM input bias current KC PHASEGND Current Limit factor Zero Crossing Comparator offset ILIM to GND = 120KΩ RILIM=120 KΩ 0.85 -2 CURRENT LIMIT AND ZERO CURRENT COMPARATOR 5 1 1.15 2 µA µA mV 0µA < IREF < 100µA 0.891 -2 0.1 0.9 0.909 +2 V mV µA PWM COMPARATOR OSC=250mV 0.4 580 0.45 ns Min. 380 220 120 Typ. 430 250 150 Max. 480 280 180 Unit ns ns ns GATE DRIVERS High side rise time High side fall time Low side rise time Low side fall time PGOOD UVP/OVP PROTECTIONS OVP UVP PGOOD PGOOD VPGOOD INTEGRATOR INT INT VSENSEVREF IVSENSE Over Voltage Clamp Under Voltage Clamp Integrator Input Offset Voltage Input Bias Current VSENSE = VCC VSENSE = GND 1.04 0.82 -5 0.1 1.07 0.84 1.1 0.86 5 V V mV µA Over voltage trip Under voltage trip Upper threshold (VSENSE/VREF) Lower threshold (VSENSE/VREF) VSENSE rising VSENSE falling ISOURCE=2mA with respect to VREF 112 66 107 86 115 69 110 89 0.14 118 72 113 92 0.2 % % % % V VDR=5V; C=7nF HGATE - PHASE from 2 to 4.5V VDR=5V; C=7nF HGATE - PHASE from 2 to 4.5V VDR=5V; C=14nF LGATE from 2 to 4.5V VDR=5V; C=14nF LGATE from 2 to 4.5V 50 50 50 50 70 70 70 70 ns ns ns ns 4/25 5V SHDN + VSENSE 1.15 VREF undervoltage comparator VSENSE 0.69 VREF IC enable pgood comparators + VSENSE VCC VSENSE 0.89 VREF HGATE BOOT V(LGATE)