ISL8240M: Dual 20A+20A and Single 40A Analog Power Module
The ISL8240M, a dual 20A/single 40A step-down power module that sets a new standard for efficiency and power density in infrastructure and embedded computing applications. Capable of delivering up to 100W of output power in a 2.9 cm2 footprint, greater than 90 percent power efficiency, and industry-leading thermal performance, the ISL8240M provides designers with a turnkey DC/DC converter solution for high current applications.
ISL8240M – Dual 20A/Single 40A Power Module
The ISL8240M is a fully-encapsulated step-down switching supply that can deliver up to 100W from a small 17mm x 17mm footprint. Operating over a wide input voltage range of 4.5V to 20V, the ISL8240M is a non-isolated module that can deliver dual 20A+20A output or a single 40A output. The ISL8240M is targeted at high current applications.
The ISL8240M is pin-to-pin compatible with the company’s popular ISL8225M 30A power module, expanding the output current to 40A and delivering up to 100W output power. This offers designers a high level of flexibility, enabling a single PCB design across platforms. The ISL8240M is also capable of delivering up to 240A output when six modules in parallel operation are current shared, enabling the industry’s highest total output current. The ISL8240M provides over-voltage protection (OVP), over-temperature protection (OTP) and over-current protection (OCP).
The wide input voltage range and high current capability make the ISL8240M an excellent choice for many infrastructure systems. The target applications are networking, telecom, data communication, wireless networking, base stations, servers, storage, and workstations that use the latest DSPs, ASICs and FPGAs. The ISL8240M can also be sold into high current ATE test equipment and industrial systems that use high current ASICs and FPGAs.
The ISL8240M module requires few external components for a complete design. External components required are input capacitors, output capacitors and resistors to program output voltage. An optional resistor can be used to change the switching frequency. The ISL8240M provides the highest output current for an encapsulated module.
The ISL8240M offers 1.5% output voltage accuracy with differential voltage remote sensing and fast transient response.
ISL8240M – Dual 20A/20A Output Application Circuit
This circuit shows a dual 20A/20A output. VOUT1 is set to 1.0V and VOUT2 is set to 1.5V. COUT2 and COUT4 are the output capacitors; they can be ceramic or electrolytic. It depends on the application. An electrolytic capacitor has larger capacitance but it has large equivalent series resistance (ESR). Electrolytic is smaller based on overall capacitance.
CIN1 and CIN2 are input capacitors. CIN1 is electrolytic and CIN2 is ceramic. CIN1 is an optional decoupling capacitor that can be used to suppress noise due to long input cables. CIN2 is a ceramic capacitor that is required for filtering. See the design guide matrix in the next slide for recommended component values.
ISL8240M – Design Guide Matrix
Note 11: EN/FF resistor is tied directly to VIN. The resistors listed here are for two channels’ EN/FF pins tied together. If separate resistor divider is used for each channel, the resistor value needs to be doubled.
Note 12: The maximum load current listed in the table is for conditions at +25°C and no air flow on a typical 4-layer evaluation board.
ISL8240M – Recommended Input/Output Capacitors
These are the recommended capacitors for the design guide matrix shown in the previous slide
ISL8240M – Single 40A Output Application Circuit
This is a single 40A output design. The output voltage is set to 1.2V and the output current is 40A.
Selection of input filter capacitors (CIN1 and CIN2) is based on how much ripple the supply can tolerate on the DC input line. The larger the capacitor, the less ripple expected; however, consideration should be given to the higher surge current.
The ISL8240M is designed for low-output voltage ripple. The output voltage ripple and transient requirements can be met with bulk output capacitors (COUT) that have adequately low ESR. COUT can be a lower ESR tantalum capacitor, a lower ESR polymer capacitor or a ceramic capacitor. The typical capacitance is 330.F. See the “Selection of Output Capacitor” section of the ISL8240M datasheet for additional information.
The remote sense lines are needed to accurately measure the output voltage. Without remote sense, there is a voltage drop in the output caused by the output trace resistance. The ISL8240M achieves 1.5% output voltage accuracy with differential remote sensing. See the recommended layout guidelines in the ISL8240M datasheet. Also, placement of output capacitors is described in the ISL8240M datasheet.
An optional snubber circuit is shown. The snubber circuit can be used for noise attenuation but it may impact efficiency.
ISL8240M – 6 Phase, 1.0V at 120A Output
This design is a 1.0V output at 120A. You can parallel three ISL8240M modules running at 40A and get 120A out. In fact, you can scale up to six modules and get up to 240A.
ISL8240M – Efficiency at VIN = 12V
This plot shows the efficiency of ISL8240M with 12V and various output voltages and load currents. The ISL8240M achieves peak efficiency above 90% for 2.5V output. The efficiency ranges anywhere from 85% for a 1V output and up to over 90% for a 2.5V output. The module can be used to generate output voltages 2.5, 1.8, 1.5, 1.2, or 1 volt very efficiently.
These are plots of derating curves. The plot on the left is a derating curve with a 5V input and the output is 1V. You can see that without any air flow the module starts derating at close to 55°C. With air flow, it is about 75°C. With 400LFM air flow it is about 85°C. There is very little IOUT output current derating at high temperatures. The curve on the right side is an example of a 12V input to 1V output. Without any air flow in this example, the module starts derating close to 50°C. With a little bit of airflow at 200LFM, it is close to about 75°C. And with 400LFM, current starts derating close to 85°C.
ISL8240M – Dual 20A/Optional 40A Evaluation Kit
The evaluation board size is 114.3mm x 76.2mm. It is a 4-layer board that contains two ounce copper on the top and bottom layers. And, it contains one ounce copper on all internal layers.
The board is designed for a dual 20A output. It can be converted to a single 40A output. The board is designed to run dual 20A output without any cooling.