L6699 Enhanced high voltage resonant controller Datasheet − production data Features ■ Symmetrical duty cycle, variable frequency control of resonant half bridge ■ Self-adjusting adaptive deadtime ■ High-accuracy oscillator ■ 2-level OCP: frequency-shift and immediate shutdown ■ Interface with PFC controller ■ Anti-capacitive-mode protection ■ Burst-mode operation at light load ■ Input for brownout protection or power-on/off sequencing ■ “Safe-start” procedure prevents hard switching at st
Contents L6699 Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 Electrical ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Electrical data . . . . . . .
L6699 List of figures List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. Figure 24. Figure 25. Figure 26. Figure 27. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Pin connections (top view) . . . . . . . . . .
Description 1 L6699 Description The L6699 is a double-ended controller specific to series-resonant half bridge topology. Both LLC and LCC configurations are supported. It provides symmetrical complementary duty cycle: the high-side switch and the low-side switch are driven ON/OFF 180° out-ofphase for exactly the same time. Output voltage regulation is obtained by modulating the operating frequency.
L6699 2 Electrical ratings Electrical ratings Table 2. 3 Absolute maximum ratings Symbol Pin Parameter Value Unit VBOOT 16 Floating supply voltage (Ileak ≤ 5µA) -1 to 618 V HVG 15 HVG voltage VOUT -0.3 to VBOOT +0.3 V VOUT 14 Floating ground voltage -3 up to a value included in the range VBOOT -18 and VBOOT V dVOUT /dt 14 Floating ground max. slew rate 50 V/ns VCC 12 IC supply voltage (Icc ≤ 25 mA) Self-limited V LVG 11 LVG voltage -0.3 to VCC +0.
Pin connections 4 L6699 Pin connections Figure 2. Pin connections (top view) &VV 9%227 '(/$< +9* &) 287 5)PLQ 1 & 67%< 9FF ,6(1 /9* /,1( *1' ',6 3)&B6723 !- V Table 4. N. 1 2 3 6/38 Pin functions Name Function CSS Soft-start.
L6699 Pin connections Table 4. N. 4 5 6 7 8 9 Pin functions (continued) Name Function RFmin Minimum oscillator frequency setting. This pin provides an accurate 2 V reference, and a resistor connected from this pin to GND defines a current that is used to set the minimum oscillator frequency. To close the feedback loop that regulates the converter output voltage by modulating the oscillator frequency, the phototransistor of an optocoupler is connected to this pin through a resistor.
Pin connections L6699 Table 4. Pin functions (continued) N. Name Function 10 GND Chip ground. Current return for both the low-side gate-drive current and the bias current of the IC. All of the ground connections of the bias components should be tied to a track going to this pin and kept separate from any pulsed current return. 11 LVG Low-side gate-drive output. The driver is capable of 0.3 A min. source and 0.8 A min. sink peak current to drive the lower MOSFET of the half bridge leg.
L6699 5 Electrical data Electrical data Tj = -25 to +125 °C, VCC = 15 V, VBOOT = 15 V, CHVG = CLVG = 1 nF; CF = 470 pF; RFmin = 12 KΩ; unless otherwise specified. Table 5. Electrical characteristics Symbol Parameter Test condition Min. Typ. Max. Unit 16 V Ic supply voltage VCC Operating range After device turn-on VCCOn Turn-on threshold Voltage rising 10 10.7 11.4 V VCCOff Turn-off threshold Voltage falling 7.45 8.15 8.85 V Hys Hysteresis VZ VCC clamp voltage 8.85 2.
Electrical data Table 5. L6699 Electrical characteristics (continued) Symbol Parameter TD (2) Deadtime self-adjustment range VCFp Peak value VCFv Valley value Test condition Voltage reference on pin 4 KM Current mirroring ratio RFmin Timing resistor range Typ. Minimum value 0.23 Maximum value 0.7 Max. Unit µs (1) VREF Min. IREF = -2 mA (1) 3.9 V 0.9 V 1.93 2 2.07 1.8 2 2.
L6699 Table 5. Electrical data Electrical characteristics (continued) Symbol Isourcepk Isinkpk Parameter Test condition Min. Typ. Max. Unit Peak source current -0.3 A Peak sink current 0.8 A tf Fall time 30 ns tr Rise time 60 ns UVLO saturation VCC = 0 to VCCOn, Isink = 2 mA 1.1 V 1.5 V High-side gate driver (voltages referred to out) VLVGL Output low voltage Isink = 200 mA VLVGH Output high voltage Isource = 5 mA Isourcepk Peak source current -0.
Application information 6 L6699 Application information The L6699 is an advanced double-ended controller specific to resonant half bridge topology. In these converters the MOSFETs of the half bridge leg are alternately switched on and off (180° out-of-phase) for exactly the same time. This is commonly referred to as symmetrical operation at “50% duty cycle”, although the real duty cycle, i.e. the ratio of the ON-time of either switch to the switching period, is actually less than 50%.
L6699 6.1 Application information Oscillator The oscillator is programmed externally by means of a capacitor (CF), connected from pin 3 (CF) to ground, that is alternately charged and discharged by the current defined with the network connected to pin 4 (RFmin). The pin provides an accurate 2 V reference with about 2 mA source capability; the higher the current sourced by the pin, the higher the oscillator frequency.
Application information L6699 After fixing CF according toTable 6: Table 6.
L6699 6.2 Application information Adaptive deadtime A deadtime TD inserted between the turn-off of either switch and the turn-on of the complementary one, where both switches are in the OFF-state, is essential to achieve softswitching. Its value must be larger than the time TT needed for the rail-to-rail swing of the half bridge midpoint.
Application information L6699 Figure 7. Adaptive deadtime: principle Figure 8. schematic 6BOO T MON O $4 END (3 ,3 " \D DT\ (6' $2)6).' ,/')# 7)4( !$!04)6% $%!$ 4)-% Relevant timing diagrams ,%6%, 3()&4%2 #BOO T /54 ,6' !- V Note that the “Driving logic…” block sets a minimum deadtime TD_MIN (≈ 230 ns) below which TD cannot go, to prevent simultaneous conduction of the high-side and the low-side switch, and also a maximum deadtime TD_MAX to guarantee proper operation of the half bridge.
L6699 Application information There are three contributors to TD: ● The turn-off delay tOFF of the Power MOSFET, which depends on the input characteristics of the specific MOSFET and the speed its gate is driven ● The transition time TT the half bridge midpoint takes for a rail-to-rail swing ● The detection time tdet that elapses from the end of the half bridge midpoint swing to the gate-drive signal of the other MOSFET going high; this includes the detection time as well as the propagation delay alon
Application information L6699 Figure 10. Comparison startup behavior: traditional controller (left), with L6699 (right) A non-zero initial voltage on the resonant capacitor may cause the very first turn-on of the high-side MOSFET to occur with non-zero drain-to-source voltage while the body diode of the low-side MOSFET is conducting, therefore invoking its reverse recovery. More hardswitching cycles may follow (see the left-hand image in Figure 10).
L6699 Application information Figure 11. Comparison of initial cycles after startup: traditional controller (left), with L6699 (right) It goes without saying that when either MOSFET is turned on for the very first time, this occurs with a non-zero drain-to-source voltage. Therefore, strictly speaking, hard-switching is still there. However, this type of one-shot hard-switching, where the body diode of the other MOSFET is not reverse recovered, is of little concern.
Application information L6699 the operating frequency is essentially determined by the current sunk by the optocoupler's phototransistor. During this frequency sweep phase the operating frequency decays following the exponential charge of CSS: then, it initially changes relatively quickly but the rate of change gets slower and slower.
L6699 7 Operation at no load or very light load Operation at no load or very light load When the resonant half bridge is lightly loaded or totally unloaded, its switching frequency reaches its maximum value. To keep the output voltage under control and avoid losing softswitching in these conditions, there must be some current flowing through the transformer's magnetizing inductance.
Operation at no load or very light load L6699 Equation 6 RFmin RFmax = 3 · 8 fmax - 1 fmin Note that, unlike the fmax considered in the Section 6.1: Oscillator, here fmax is associated to some load PoutB greater than the minimum one. PoutB is normally such that the transformer's peak currents are low enough not to cause audible noise.
L6699 Operation at no load or very light load Figure 17.
Current sensing, OCP and OLP 8 L6699 Current sensing, OCP and OLP In the L6699 the current sense input ISEN (pin 6) senses the current flowing in the resonant tank to perform multiple tasks: 1. Primary overcurrent protection (OCP function). 2. Hard-switching cycles prevention at startup (see Section 6.3: Safe-start procedure). 3. Capacitive-mode detection during operation (see Section 9: Capacitive-mode detection function). In this section the discussion is concentrated on the OCP function.
L6699 Current sensing, OCP and OLP The ISEN pin, which is also able to withstand negative voltages, is internally connected to the input of a first comparator, referenced to VISENx (0.8 V typ. 0.76 V min.), and to that of a second comparator referenced to 1.5 V. The operation of the second comparator is described later. If the voltage externally applied to the pin by either circuit in Figure 18 and 19 exceeds 0.
Current sensing, OCP and OLP L6699 therefore providing the system with immunity to short duration phenomena. If, instead, TSH is exceeded, an overload protection (OLP) procedure is activated that shuts down the L6699 and, in case of continuous overload/short-circuit, results in continuous intermittent operation with a user-defined duty cycle. This function is realized on pin 2 (DELAY), with a capacitor CDelay and a parallel resistor RDelay connected to ground. As the voltage on the ISEN pin exceeds 0.
L6699 Current sensing, OCP and OLP Figure 20. Soft-start and delayed shutdown upon overcurrent timing diagram (safestart details are not shown) ). #!3% , )3 3%,& 3500,)%$ 6CC 4 3( #SS )3%. 6 4 -0 4 34/0 T 4 SS T 6 6 $%,!9 T 6 6 6 T 6OUT T 0&#?34/0 34!24 50 3/&4 34!24 ./2-!, /0%2!4)/. /6%2 ,/!$ ./2-!, /0%2!4)/. /6%2,/!$ 3(54$/7. 3/&4 34!24 T -).
Capacitive-mode detection function 9 L6699 Capacitive-mode detection function Normally, the resonant half bridge converter operates with the resonant tank current lagging behind the square-wave voltage applied by the half bridge leg, like a circuit having a reactance of an inductive nature.
L6699 Capacitive-mode detection function 4. When either MOSFET is turned on, the other one can be parasitically turned on too, if the current injected through its Cgd and flowing through the gate driver's pull-down is large enough to raise the gate voltage close to the turn-on threshold This would be a lethal shoot-through condition for the half bridge leg. 5.
Line sensing function 10 L6699 Line sensing function This function basically stops the IC as the input voltage to the converter falls below the specified range and lets it restart as the voltage goes back within the range.
L6699 Line sensing function Figure 22. Line sensing function: internal block diagram and timing diagram (6 )NP UT BUS 6IN/. 6IN/&& ,).% T 6 (6 )NP UT BUS T 6CC 6IN/+ ) (93 2( ,).
Latched shutdown 11 L6699 Latched shutdown The L6699 is equipped with a comparator having the non-inverting input externally available on pin 8 (DIS) and with the inverting input internally referenced to 1.85 V. As the voltage on the pin exceeds the internal threshold, the IC is immediately shut down, the PFC_STOP pin is asserted low and the quiescent consumption reduced to a low value.
L6699 Bootstrap section Figure 23. Bootstrap supply: standard circuit Figure 24. Bootstrap supply: internal bootstrap synchronous diode $"//4 , 6CC 6CC 6"//4 6"//4 #"//4 #"//4 ,6' /54 /54 !- V !- V This concern applies to converters designed with a high resonance frequency (indicatively, > 150 kHz), so that they run at high frequency also at full load.
Package information 13 L6699 Package information In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com. ECOPACK is an ST trademark. Figure 25. SO16N dimensions mm Dim. Min. Typ. A 1.75 A1 0.10 0.25 A2 1.25 b 0.31 0.51 c 0.17 0.25 D 9.80 9.90 10.00 E 5.80 6.00 6.20 E1 3.80 3.90 4.
L6699 Package information Figure 26.
Package information L6699 Figure 27.
L6699 14 Revision history Revision history Table 7. Document revision history Date Revision Changes 12-Apr-2012 1 Initial release. 16-Jan-2013 2 Updated Table 2: Absolute maximum ratings on page 5.
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