E-L6911C STMicroelectronics, E-L6911C Datasheet
E-L6911C
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E-L6911C Summary of contents
Page 1
... An external SCR is triggered to crowbar the input supply in case of hard over-voltage. An internal crowbar is also provided turning on the low side mosfet as long as the over- voltage is detected. In case of over-current detection, the soft start capacitor is discharged and the system works in HICCUP mode. ...
Page 2
... Symbol GND, PGND Boot Voltage BOOT PHASE V -V HGATE PHASE OCSET, LGATE, PHASE RT, SS, FB, PGOOD, VSEN, VID0-4 OVP, COMP THERMAL DATA Symbol R Thermal Resistance Junction to Ambient th j-amb T Maximum junction temperature j T Storage temperature range stg T Junction temperature range J PIN CONNECTION (Top view) ...
Page 3
... GND All the internal references are referred to this pin. Connect it to the PCB signal ground. 12 PGOOD This pin is an open collector output and is pulled low if the output voltage is not within the above specified thresholds. If not used may be left floating. 13 PHASE This pin is connected to the source of the upper mosfet and provides the return path for the high side driver ...
Page 4
... PGOOD Voltage Low PGOOD 4/20 = 12V 25°C unless otherwise specified) CC amb Test Condition UGATE and LGATE open VOCSET=4.5V VOCSET=4. OPEN < GND < 200 OPEN T VID0, VID1, VID2, VID3, VID4 see Table1; Tamb = COMP=10pF =12V, BOOT PHASE UGATE PHASE V -V =12V, BOOT PHASE I = 300mA UGATE ...
Page 5
... PWM charging and discharging with a constant current an internal capacitor. The current delivered to the oscillator is typically 50 A (Fsw=200KHz) and may be varied using an external resistor (R RT pin and GND or VCC. Since the RT pin is maintained at fixed voltage (typ. 1.235V), the frequency is varied proportionally to the current sunk (forced) from (into) the pin. ...
Page 6
... The DAC output is delivered to an amplifier obtaining the V set-point of the error amplifier). Internal pull-ups are provided (realized with current generator); in this way, to program a logic "1" enough to leave the pin floating, while to program a logic "0" enough to short the pin to GND. ...
Page 7
... PHASE pin is over about 500mV. The upper mos is in any case turned-on after 200nS from the low side turn-off. The peak current is shown for both the upper (fig. 3) and the lower (fig. 4) driver at 5V and 12V. A 4nF capacitive load has been used in these measurements. ...
Page 8
... CH1 = Low Side Gate Monitoring and Protections The output voltage is monitored by means of pin 1 (VSEN not within ±12% (typ.) of the programmed value, the powergood output is forced low. The device provides overvoltage protection, when the output voltage reaches a value 17% (typ.) grater than the nominal one ...
Page 9
... If the compensation network is well designed, the device is able to open or close the duty cycle up to 100% or down to 0%. The response time is now the time required by the inductor to change its current from initial to final value. Since the inductor has not finished its charging time, the output cur- rent is supplied by the output capacitors ...
Page 10
... Input Capacitor The input capacitor has to sustain the ripple current produced during the on time of the upper MOS must have a low ESR to minimize the losses. The rms value of this ripple is: Where D is the duty cycle ...
Page 11
... NOM (a) As shown in figure 6, the ESR drop is present in any case, but using the droop function the total deviation of the output voltage is minimized. In practice the droop function introduces a static error (Vdroop in figure 6) propor- tional to the output current. Since a sense resistor is not present, the output DC current is measured by using the intrinsic resistance of the inductance (a few m ) ...
Page 12
... R sient is minimum when the output impedance is constant with frequency. To choose the other components of the compensation network, the transfer function of the voltage loop is con- sidered. To simplify the analysis is supposed that R3 << Rd, where Rd = (R8//R9). Figure 8. Compensation network definition ...
Page 13
... To understand the reason of the previous assumption, the scheme in figure 9 must be considered. In this scheme, the inductor current has been substituted by the load current, because in the frequencies range of interest for the Droop function these current are substantially the same and it was supposed that the droop network don't represent a charge for the inductor. ...
Page 14
... The device is supplied by the 12V input rail while the power conversion starts from the 5V input rail. The device is also able to operate with a 5V supply voltage; in this case 12V input can be directly connected to the 5V power source. The four layers demo board's copper thickness order to minimize conduction losses considering the high current that the circuit is able to deliver ...
Page 15
... IC supply voltage of 5V and 12V. In the application two mosfets STS12NF30L (30V, 10m both the low and the high side. The board has been layed out with the possibility to use up to three SO8 mosfets for both high and low side 2 switch. Two D PACK mosfets (one for each high and low side) may also be used in order to allow the maximum flexibility in meeting different requirements ...
Page 16
... L6911C Inductor selection Since the maximum output current is equal to 14A, to have a 30% ripple (4A) in worst case inductor has been chosen. So the ripple is 4.1A @ 3.5V with V In worst case the peak is equal to 18.1A. Output Capacitor In the demo ten Sanyo capacitors, model 6MV1000GX are used, with a maximum ESR equal to 69m . There- fore, the resultant ESR is 69m / ...
Page 17
... PCB AND COMPONENTS LAYOUTS Figure 14. PCB and Components Layouts Component Side Figure 15. PCB and Components Layouts Internal Layer Internal Ground Plane Solder Side L6911C 17/20 ...
Page 18
... L6911C Application Circuit Examples Figure 16 reports the schematic circuit for a motherboard chipset power supply. This application works from a single 5V power supply and is able to deliver up to 10A with a 300KHz switching frequency. Figure 16. Motherboard chipset power supply; 2.5Vout, 10A CoilCraft DO3316P 1uH 10A fuse ...
Page 19
... E 7.4 7.6 0.291 e 1. 10.65 0.394 h 0.25 0.75 0.010 L 0.4 1.27 0.016 K 0˚ (min.)8˚ (max inch MECHANICAL DATA TYP. MAX. 0.104 0.012 0.020 0.013 0.512 0.299 0.050 0.419 0.030 0.050 L6911C OUTLINE AND SO20 h x 45˚ SO20MEC 19/20 ...
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