ISL6745 ® Data Sheet September 1, 2005 Bridge Controller with Precision Dead Time Control The ISL6745 is a low-cost double-ended voltage-mode PWM controller designed for half-bridge and full-bridge power supplies and line-regulated bus converters. It provides precise control of switching frequency, adjustable soft-start, and overcurrent shutdown. In addition, the ISL6745 allows for accurate adjustment of MOSFET nonoverlap time (“deadtime”) with deadtimes as low as 35ns, allowing power engineers to optimize the efficiency of openloop bus converters. The ISL6745 also includes a control voltage input for closed-loop PWM and line voltage feedforward functions. Low start-up and operating currents allow for easy biasing in both AC/DC and DC/DC applications. This advanced BiCMOS design also features adjustable switching frequency up to 1MHz, 1A FET drivers, and very low propagation delays for a fast response to overcurrent faults. The ISL6745 is available in a space-saving MSOP-10 package and is guaranteed to meet rated specifications over a wide -40°C to 105°C temperature range. Ordering Information PART NUMBER TEMP. RANGE (°C) Features • Precision Duty Cycle and Deadtime Control • 100µA Start-up Current • Adjustable Delayed Overcurrent Shutdown and Re-Start • Adjustable Oscillator Frequency Up to 2MHz • 1A MOSFET Gate Drivers • Adjustable Soft-Start • Internal Over Temperature Protection • 35ns Control to Output Propagation Delay • Small Size and Minimal External Component Count • Input Undervoltage Protection • Pb-Free Plus Anneal Available (RoHS Compliant) Applications • Half-bridge Converters • Full-bridge Converters • Line-regulated Bus Converters • AC/DC Power Supplies PKG. DWG. # PACKAGE ISL6745AU -40 to 105 10 Ld MSOP M10.118 ISL6745AUZ (See Note) -40 to 105 10 Ld MSOP (Pb-free) M10.118 Add -T suffix to part number for tape and reel packaging • Telecom, Datacom, and File Server Power Pinout ISL6745 (MSOP) TOP VIEW SS 1 NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. 1 FN9161.6 10 VDD RTD 2 9 VDDP VERR 3 8 OUTB CS 4 7 OUTA CT 5 6 GND CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2004-2005. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Internal Architecture VDDP FL VBIAS VBIAS 5.00 V VDD OUTA Q UVLO + BG T Q OUTB PWM TOGGLE VBIAS INTERNAL OT SHUTDOWN 130 - 150 C 70 uA ON SS VBIAS + - SS CLAMP RTD - 2.0 V IRTD + - + 15 uA SS CHARGED 3.9 V 4.0 V VBIAS S Q R Q ISL6745 160 uA OC LATCH ON - 2.8 V PEAK + CT 0.8 V I DCH= 55 x IRTD 2 GND S Q R Q CLK Q RESET DOMINANT VALLEY + SS LOW Q 50 µS RETRIGGERABLE ONE SHOT FAULT LATCH SET DOMINANT S Q IDCH R Q S Q R Q PWM LATCH SET DOMINANT ON VBIAS UV + BG 0.6 V + - OC DETECT PWM COMPARATOR VBIAS CT 15 uA VERR + - SS 0.8 0.8 SS FL VBIAS 4.65V ↓ 4.80V ↑ CS 0.27 V + - ISL6745 Absolute Maximum Ratings Thermal Information Supply Voltage, VDD . . . . . . . . . . . . . . . . . . . GND - 0.3V to +20.0V OUTA, OUTB . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to VDD Signal Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to 5V Peak GATE Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1A ESD Classification Human Body Model (Per JEDEC22 std. Method A114-B) . Class 2 Machine Model (Per JEDEC22 std. Method A115-A). . . . .Class A Thermal Resistance (Typical, Note 1) θJA (°C/W) 10 Lead MSOP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Maximum Junction Temperature . . . . . . . . . . . . . . . . -55°C to 150°C Maximum Storage Temperature Range . . . . . . . . . . . -65°C to 150°C Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300°C Operating Conditions Temperature Range ISL6745AU . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to 105°C Supply Voltage Range (Typical). . . . . . . . . . . . . . . . . . . . 9-16 VDC CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTES: 1. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details. 2. All voltages are to be measured with respect to GND, unless otherwise specified. Electrical Specifications Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application schematic. 9V < VDD< 16V, RTD = 51.1kΩ, CT = 470pF, TA = -40°C to 105°C (Note 4), Typical values are at TA = 25°C PARAMETER TEST CONDITIONS MIN TYP MAX UNITS SUPPLY VOLTAGE Start-Up Current, IDD VDD< START Threshold - - 175 µA Operating Current, IDD COUTA,B = 1nF - 5 8.5 mA UVLO START Threshold 5.9 6.3 6.6 V UVLO STOP Threshold 5.3 5.7 6.3 V - 0.6 - V 0.55 0.6 0.65 V - 35 - ns CS Sink Current 8 10 - mA Input Bias Current -1 - 1 µA Hysteresis CURRENT SENSE Current Limit Threshold CS to OUT Delay (Note 4) PULSE WIDTH MODULATOR Minimum Duty Cycle VERROR < CT Offset - - 0 % Maximum Duty Cycle CT = 470pF, RTD = 51.1kΩ - 94 - % CT = 470pF, RTD = 1.1kΩ (Note 4) - 99 - % - 0.8 - V/V VERR to PWM Comparator Input Gain CT to PWM Comparator Input Gain (Note 4) - 1 - V/V SS to PWM Comparator Input Gain (Note 4) - 0.8 - V/V 3 ISL6745 Electrical Specifications Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application schematic. 9V < VDD< 16V, RTD = 51.1kΩ, CT = 470pF, TA = -40°C to 105°C (Note 4), Typical values are at TA = 25°C (Continued) PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 143 156 170 µA 1.925 2 2.075 V 45 - 65 µA/µA CT Valley Voltage 0.75 0.8 0.85 V CT Peak Voltage 2.70 2.80 2.90 V Net Charging Current 45 - 68 µA SS Clamp Voltage 3.8 4.0 4.2 V - 3.9 - V 12 15 23 µA 0.25 0.27 0.30 V OSCILLATOR Charge Current TA = 25°C RTD Voltage Discharge Current Gain SOFT-START Overcurrent Shutdown Threshold Voltage (Note 4) Overcurrent Discharge Current Reset Threshold Voltage (Note 4) OUTPUT High Level Output Voltage (VOH) VDD - VOUTA or VOUTB, IOUT = -100mA - 0.5 2.0 V Low Level Output Voltage (VOL) IOUT = 100mA - 0.5 1.0 V Rise Time CGATE = 1nF, VDD = 12V - 17 60 ns Fall Time CGATE = 1nF, VDD = 12V - 20 60 ns Thermal Shutdown (Note 4) - 145 - °C Thermal Shutdown Clear (Note 4) - 130 - °C Hysteresis, Internal Protection (Note 4) - 15 - °C THERMAL PROTECTION NOTES: 3. Specifications at -40°C are guaranteed by design, not production tested. 4. Guaranteed by design, not 100% tested in production. 4 ISL6745 Typical Performance Curves 1-104 CT = 1000pF 680pF 470pF 60 DEADTIME (ns) CT DISCHARGE CURRENT GAIN 65 55 50 1-103 CT = 270pF CT = 100pF 100 45 40 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 10 RTD CURRENT (mA) 10 FIGURE 1. OSCILLATOR CT DISCHARGE CURRENT GAIN 40 50 60 RTD (kΩ) 70 80 90 100 1.03 NORMALIZED CHARGING CURRENT OSCILLATOR FREQUENCY (kHz) 30 FIGURE 2. DEADTIME vs CAPACITANCE 600 500 400 300 200 100 0 100 20 200 300 400 500 600 CT (pF) 700 800 900 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95 -40 1000 -25 -10 5 20 FIGURE 3. CAPACITANCE vs OSCILLATOR FREQUENCY (RTD = 49.9kΩ) 1.06 NORMALIZED VOLTAGE 50 65 80 95 FIGURE 4. CHARGE CURRENT vs TEMPERATURE 1.07 1.05 1.04 1.03 1.02 1.01 1.00 0.99 0.98 0 10 20 30 40 50 60 70 80 RTD (kΩ) FIGURE 5. TIMING CAPACITOR VOLTAGE vs RTD 5 35 TEMPERATURE (°C) 90 100 110 ISL6745 Pin Descriptions VDD - VDD is the power connection for the IC. To optimize noise immunity, bypass VDD to GND with a ceramic capacitor as close to the VDD and GND pins as possible. The total supply current, IDD, will be dependent on the load applied to outputs OUTA and OUTB. Total IDD current is the sum of the quiescent current and the average output current. Knowing the operating frequency, FSW, and the output loading capacitance charge, Q, per output, the average output current can be calculated from: I OUT = 2 • Q • F SW A (EQ. 1) RTD - This is the oscillator timing capacitor discharge current control pin. A resistor is connected between this pin and GND. The current flowing through the resistor determines the magnitude of the discharge current. The discharge current is nominally 55x this current. The PWM deadtime is determined by the timing capacitor discharge duration. CT - The oscillator timing capacitor is connected between this pin and GND. CS - This is the input to the overcurrent protection comparator. The overcurrent comparator threshold is set at 0.600V nominal. The CS pin is shorted to GND at the end of each switching cycle. Depending on the current sensing source impedance, a series input resistor may be required due to the delay between the internal clock and the external power switch. Exceeding the overcurrent threshold will start a delayed shutdown sequence. Once an overcurrent condition is detected, the soft-start charge current source is disabled. The soft-start capacitor begins discharging through a 15µA current source, and if it discharges to less than 3.9V (Sustained Overcurrent Threshold), a shutdown condition occurs and the OUTA and OUTB outputs are forced low. When the soft-start voltage reaches 0.27V (Reset Threshold) a soft-start cycle begins. If the overcurrent condition ceases, and then an additional 50µs period elapses before the shutdown threshold is reached, no shutdown occurs. The SS charging current is reenabled and the soft-start voltage is allowed to recover. GND - Reference and power ground for all functions on this device. Due to high peak currents and high frequency operation, a low impedance layout is necessary. Ground planes and short traces are highly recommended. OUTA and OUTB - Alternate half cycle output stages. Each output is capable of 1A peak currents for driving power MOSFETs or MOSFET drivers. Each output provides very low impedance to overshoot and undershoot. SS - Connect the soft-start timing capacitor between this pin and GND to control the duration of soft-start. The value of the capacitor determines the rate of increase of the duty cycle during start-up, controls the overcurrent shutdown delay, and the overcurrent and short circuit hiccup restart period. VERR - The inverting input of the PWM comparator. The error voltage is applied to this pin to control the duty cycle. Increasing the signal level increases the duty cycle. The node may be driven with an external error amplifier or an opto-coupler. VDDP - VDDP is the separate collector supply to the gate drive. Having a separate VDDP pin helps isolate the analog circuitry from the high power gate drive noise. Functional Description Features The ISL6745 PWM is an excellent choice for low cost bridge topologies for applications requiring accurate frequency and deadtime control. Among its many features are 1A FET drivers, adjustable soft-start, overcurrent protection and internal thermal protection, allowing a highly flexible design with minimal external components. Oscillator The ISL6745 has an oscillator with a frequency range to 2MHz, programmable using a resistor RTD and capacitor CT. The switching period may be considered to be the sum of the timing capacitor charge and discharge durations. The charge duration is determined by CT and the internal current source (assumed to be 160µA in the formula). The discharge duration is determined by RTD and CT. 4 T C ≈ 1.25 ×10 • C T s (EQ. 2) 1 T D ≈ ----------------------------------------------------------------------------- • R TD • C T CTDisch arg eCurrentGain 1 T OSC = T C + T D = ---------------F OSC s (EQ. 3) (EQ. 4) where TC and TD are the approximate charge and discharge times, respectively, TOSC is the oscillator free running period, and FOSC is the oscillator frequency. One output switching cycle requires two oscillator cycles. The actual times will be slightly longer than calculated due to internal propagation delays of approximately 5ns/transition. This delay adds directly to the switching duration, and also causes overshoot of the timing capacitor peak and valley voltage thresholds, effectively increasing the peak-to-peak voltage on the timing capacitor. Additionally, if very low charge and discharge currents are used, there will be an increased error due to the input impedance at the CT pin. The above formulae help with the estimation of the frequency. Practically, effects like stray capacitances that affect the overall CT capacitance, variation in RTD voltage and charge current over temperature, etc. exist, and are best evaluated in-circuit. Equation 2 follows from the basic dV capacitor current equation, i = C × . In this case, with dt 6 s ISL6745 variation in dV with RTD (Figure 5), and in charge current (Figure 4), results from Equation 2 would differ from the calculated frequency. The typical performance curves may be used as a tool along with the previous equations as a more accurate tool to estimate the operating frequency more accurately. The maximum duty cycle, D, and deadtime, DT, can be calculated from: D = T C ⁄ T OSC DT = ( 1 – D ) ⋅ T OSC (EQ. 5) s (EQ. 6) Soft-Start Operation The ISL6745 features a soft-start using an external capacitor in conjunction with an internal current source. Soft-start reduces stresses and surge currents during start-up. The oscillator capacitor signal, CT, is compared to the softstart voltage, SS, in the SS comparator which drives the PWM latch. While the SS voltage is less than 3.5V, duty cycle is limited. The output pulse width increases as the softstart capacitor voltage increases up to 3.5V. This has the effect of increasing the duty cycle from zero to the maximum pulse width during the soft-start period. When the soft-start voltage exceeds 3.5V, soft-start is completed. Soft-start occurs during start-up and after recovery from an overcurrent shutdown. The soft-start voltage is clamped to 4V. Gate Drive The ISL6745 is capable of sourcing and sinking 1A peak current, and may also be used in conjunction with a MOSFET driver such as the ISL6700 for level shifting. To limit the peak current through the IC, an external resistor may be placed between the totem-pole output of the IC (OUTA or OUTB pin) and the gate of the MOSFET. This small series resistor also damps any oscillations caused by the resonant tank of the parasitic inductances in the traces of the board and the FET’s input capacitance. 7 Overcurrent Operation Overcurrent delayed shutdown is enabled once the soft-start cycle is complete. If an overcurrent condition is detected, the soft-start charging current source is disabled and the softstart capacitor is allowed to discharge through a 15µA source. At the same time a 50µs retriggerable one-shot timer is activated. It remains active for 50µs after the overcurrent condition ceases. If the soft-start capacitor discharges to 3.9V, the output is disabled. This state continues until the soft-start voltage reaches 270mV, at which time a new softstart cycle is initiated. If the overcurrent condition stops at least 50µs prior to the soft-start voltage reaching 3.9V, the soft-start charging currents revert to normal operation and the soft-start voltage is allowed to recover. Thermal Protection An internal temperature sensor protects the device should the junction temperature exceed 145°C. There is approximately 15°C of hysteresis. Ground Plane Requirements Careful layout is essential for satisfactory operation of the device. A good ground plane must be employed. VDD should be bypassed directly to GND with good high frequency capacitance. ISL6745 Mini Small Outline Plastic Packages (MSOP) N M10.118 (JEDEC MO-187BA) 10 LEAD MINI SMALL OUTLINE PLASTIC PACKAGE E1 INCHES E -B- INDEX AREA 1 2 0.20 (0.008) A B C TOP VIEW 4X θ 0.25 (0.010) R1 R GAUGE PLANE SEATING PLANE -CA 4X θ A2 A1 b -H- 0.10 (0.004) L SEATING PLANE C MIN MAX MIN MAX NOTES A 0.037 0.043 0.94 1.10 - A1 0.002 0.006 0.05 0.15 - A2 0.030 0.037 0.75 0.95 - b 0.007 0.011 0.18 0.27 9 c 0.004 0.008 0.09 0.20 - D 0.116 0.120 2.95 3.05 3 E1 0.116 0.120 2.95 3.05 4 0.020 BSC 0.20 (0.008) C C a SIDE VIEW CL E1 0.20 (0.008) C D - 0.187 0.199 4.75 5.05 - L 0.016 0.028 0.40 0.70 6 0.037 REF N -A- 0.50 BSC E L1 e D SYMBOL e L1 MILLIMETERS 0.95 REF 10 R 0.003 R1 - 10 - 0.07 0.003 - θ 5o 15o α 0o 6o 7 - - 0.07 - - 5o 15o - 0o 6o -B- Rev. 0 12/02 END VIEW NOTES: 1. These package dimensions are within allowable dimensions of JEDEC MO-187BA. 2. Dimensioning and tolerancing per ANSI Y14.5M-1994. 3. Dimension “D” does not include mold flash, protrusions or gate burrs and are measured at Datum Plane. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension “E1” does not include interlead flash or protrusions and are measured at Datum Plane. - H - Interlead flash and protrusions shall not exceed 0.15mm (0.006 inch) per side. 5. Formed leads shall be planar with respect to one another within 0.10mm (.004) at seating Plane. 6. “L” is the length of terminal for soldering to a substrate. 7. “N” is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. Dimension “b” does not include dambar protrusion. Allowable dambar protrusion shall be 0.08mm (0.003 inch) total in excess of “b” dimension at maximum material condition. Minimum space between protrusion and adjacent lead is 0.07mm (0.0027 inch). 10. Datums -A -H- . and - B - to be determined at Datum plane 11. Controlling dimension: MILLIMETER. Converted inch dimensions are for reference only All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see www.intersil.com 8