APPLICATION NOTE AN9404 Rev.3.00 HIP4080A, 80V High Frequency H-Bridge Driver Dec 11, 2007 current reference with a signal proportional to load current Introduction through resistor, R , which comes from a differential 4 The HIP4080A is a member of the HIP408x family of High amplifier, A1. A bias voltage of 6V (represents half of the Frequency H-Bridge Driver ICs. A simplified application bias voltage and the maximum rail to rail voltage of the diagram of the HIP4080A IC is shown in Figure 1. The comparator and amplifier, A1) biases the comparators IN+ HIP408x family of H-Bridge driver ICs provide the ability to terminal through R and the amplifier, A1s, positive 2 operate from 10VDC to 80VDC busses for driving H-Bridges, summing junction. whose switch elements are comprised of power N-Channel 80V MOSFETs. The HIP408X family, packaged in both 20 Ld DIP and 20 Ld SOIC DIPs, provide peak gate current drive of 2.5A. The HIP4080A includes undervoltage protection, 12V which sends a continuous gate turn-off pulse to all gate outputs when the V voltage falls below a nominal 8.25V. DD The startup sequence of the HIP4080A is initiated when the V voltage returns above a nominal 8.75V. Of course, the DD DIS pin must be in the low state for the IC to be enabled. The startup sequence turns on both low side outputs, ALO and HIP4080A BLO, so that the bootstrap capacitors for both sides of the H-bridge can be fully charged. During this time the AHO and BHO gate outputs are held low continuously to insure that no shoot-through can occur during the nominal 400ns boot-strap refresh period. At the end of the boot strap refresh period the outputs respond normally to the state of the input control GND GND signals. FIGURE 1. HIP4080A SIMPLIFIED APPLICATION A combination of bootstrap and charge-pumping techniques DIAGRAM is used to power the circuitry which drives the upper halves of the H-Bridge. The bootstrap technique supplies the high instantaneous current needed for turning on the power +80V devices, while the charge pump provides enough current to maintain bias voltage on the upper driver sections and MOSFETs. Since voltages on the upper bias supply pin float along with the source terminals of the upper power switches, the design of this family provides voltage capability for the upper bias supply terminals to 95VDC. HIP408x The HIP4080A can drive lamp loads for automotive and industrial applications as shown in Figure 2. When inductive loads are switched, flyback diodes must be placed around the loads to protect the MOSFET switches. Many applications utilize the full bridge topology. These are voice coil motor drives, stepper and DC brush motors, audio GND amplifiers and even power supply inverters used in uninterruptable power supplies, just to name a few. Of the above, voice coil motor drives and audio amplifiers can take FIGURE 2. HIP4080A AS LAMP SWITCH DRIVER, DUAL advantage of the built-in comparator available in the HIGH/LOW SWITCHES FOR AUTOMOTIVE AND INDUSTRIAL CONTROLS HIP4080A. Using the output of the comparator to add some positive feedback, a hysteresis control, so popular with voice coil motor drivers, can be implemented as shown in Figure 1. In the figure, R is fed back from the comparator output, 3 OUT, to the positive input of the comparator, IN+. Capacitor, C1, integrates in a direction to satisfy the reference current signal at IN. The IN- input of the comparator sums this AN9404 Rev.3.00 Page 1 of 14 Dec 11, 2007HIP4080A, 80V High Frequency H-Bridge Driver When no current is flowing in either direction in the load, the switch only the lower H-bridge MOSFETs. When HEN is high output of A1 is exactly 6V. The reference input, IN, would both upper and lower MOSFETs of the also have to be 6V to request zero current from the bridge. H-bridge are switched. The HEN input can also be H-switched with the IN+ and IN- inputs used only for direction control, The bridge would still switch in this case, because of the thereby minimizing switching losses. positive feedback connection of the HIP4080A internal comparator. The frequency of oscillation of the output will be Description of the HIP4080A a function of the amount of dc hysteresis gain, R /R and the 3 1 The block diagram of the HIP4080A relating to driving the size of capacitor, C . As the capacitor, C , is made larger, 1 1 A-side of the H-Bridge is shown in Figure 4. The blocks the steady-state frequency of the bridge will become smaller. associated with each side of the H-Bridge are identical, so It is beyond the scope of this application note to provide a full the B-side is not shown for simplicity. analysis. A valuable characteristic of hysteresis control is that as the error becomes smaller (i.e. the reference and The two bias voltage terminals, V and V , on the CC DD feedback signals match) the frequency increases. Usually HIP4080A should be tied together. They were separated this occurs when the load current is small or at a minimum. within the HIP4080A to avoid possible ground loops internal When the error signal is large, the frequency becomes very to the IC. Tieing them together and providing a decoupling small, perhaps even DC. One advantage of this is that when capacitor from the common tie-point to V greatly improves SS currents are largest, switching losses are a minimum, and noise immunity. when switching losses are largest, the dc current component Input Logic is small. The HIP4080A accepts inputs which control the output state The HIP408x family of devices is fabricated using a of the power MOSFET H-bridge and provides a comparator proprietary Intersil IC process which allows this family to output pin, OUT, which can provide compensation or switch at frequencies of over 500kHz. Therefore the hysteresis. HIP408x family is ideal for use in Voice coil motor, switching The DIS, Disable, pin disables gate drive to all H-bridge power amplifier, DC/DC converters and high performance MOSFETs regardless of the command states of the input AC/DC and step-motor control applications. pins, IN+, IN and HEN. The state of the bias voltage, V , DD To provide accurate dead-time control for the twin purposes also can disable all gate drive as discussed in the of shoot-through avoidance and duty-cycle maximization, introduction. The HEN, High Enable, pin enables and two resistors tied to pins HDEL and LDEL provide precise disables gate drive to the two high side MOSFETs. A high delay matching of upper and lower propagation delays, level on the HEN pin enables high side gate drive as which are typically only 55ns. The HIP408x family of further determined by the states of the IN+ and IN H-bridge drivers has enough voltage margin to be applied to comparator input pins, since the IN+ and IN pins control all SELV (UL classification for operation at 42.0V) which diagonal pair of MOSFETs are gated. Upper drive can applications and most Automotive applications where load be modulated through use of the HEN pin while drive to dump capability over 65V is required. This capability makes diagonally opposing lower MOSFETs is continuous. To the HIP408x family a more cost-effective solution for driving simultaneously modulate both upper and lower drivers, HEN N-Channel power MOSFETs than either discrete solutions or is continuously held high while modulating the IN+ and IN other solutions relying on transformer- or opto-coupling gate- pins. drive techniques as shown in Figure 1. Modulating only the upper switches can nearly halve the The HIP4080A differs from the HIP4081A regarding the switching losses in both the driver IC and in the lower function of pins 2, 5, 6 and 7 of the IC and the truth table MOSFETs. The power dissipation saved at high switching which governs the switching function of the two ICs. In the frequencies can be significant. Table 1 summarizes the input HIP4080A, pins 2, 5, 6 and 7 are labeled HEN, OUT, IN+ control logic. and IN-, respectively. In the HIP4081A, pins 2, 5, 6 and 7 are labeled BHI (B-side high input), BLI (B-side low input), ALI (A-side low input) and AHI (A-side high input), respectively. The HIP4081As inputs individually control each of the four power MOSFETs, or in pairs (excepting the shoot-through case). The HIP4080A provides an internal comparator and a high enable...HEN pin. The comparator can be used to provide a PWM logic signal to switch the appropriate MOSFETs within the H-bridge, and can facilitate Hysteresis control to be illustrated later. The HEN pin enables (when HEN is high) or disables (when HEN is low) the A-side and B-side upper MOSFETs. With HEN held low, it is possible to AN9404 Rev.3.00 Page 2 of 14 Dec 11, 2007