USERS MANUAL ISL7823xEVAL1Z UG015 Rev 2.00 Evaluation Board User Guide October 26, 2016 Description Key Features The ISL78233EVAL1Z, ISL78234EVAL1Z, and ISL78235EVAL1Z 2.7V to 5.5V input voltage range evaluation boards are used to demonstrate the performance of Synchronous buck regulator up to 95% efficiency the ISL78233, ISL78234, and ISL78235 low quiescent current, 1% reference accuracy over temperature high efficiency synchronous buck regulators. The evaluation boards are intended for use by customers with requirements for Resistor adjustable frequency from 500kHz to 4MHz point-of-load automotive applications with 2.7V to 5.5V input Default set to 2MHz supply voltage, output voltages down to 0.8V and up to 5A output External synchronization from 1MHz to 4MHz current. 100ns maximum phase minimum on time allows wide The ISL78233, ISL78234, and ISL78235 are offered in a output regulation operating at 2MHz 3x3mm 16 Ld TQFN package with 1mm maximum height. The Internal soft-start set to 1ms adjustable with external complete area that the regulator occupies can be as small as 2 soft-start capacitor 0.22in . Over-temperature, overcurrent, overvoltage, and negative overcurrent protection Specifications I V V OUT IN OUT Related Literature PART (MAX) f RANGE RANGE RANGE PART SIZE SW For a full list of related documents please visit our website NUMBER (A) (MHz) (V) (V) (mm) - ISL78233, ISL78234, ISL78235 product pages ISL78235 5 Programmable 2.7 to 0.8 to ISL78234 4 3x3 Ordering Information 1to4 5.5 5.5 ISL78233 3 PART NUMBER DESCRIPTION PCB SPECIFICATION ISL78235EVAL1Z Evaluation Board for 5A Sync Buck ISL78235 Board dimension: 2.025 x 2.725 in of Layers: 4 ISL78234EVAL1Z Evaluation Board for 4A Sync Buck ISL78234 FR-4 Thickness: 1.57mm ISL78233EVAL1Z Evaluation Board for 3A Sync Buck ISL78233 Copper Weight: 2oz. NOTES: 1. The evaluation board default V = 1.8V. OUT 2. The evaluation board default f = 2MHz. SW FIGURE 1. ISL78235EVAL1Z EVALUATION BOARD PHOTO UG015 Rev 2.00 Page 1 of 9 October 26, 2016ISL7823xEVAL1Z 2.1A current source sets the soft-start interval of the converter, Recommended Equipment t . SS The following equipment is recommended to perform testing: C F = 3.5 t s (EQ. 3) SS SS 0V to 5V power supply with 10A source current capability C should be no more than 33nF to insure proper soft-start SS Electronic load capable of sinking current up to 10A reset after fault condition. The ISL78233EVAL1Z, Digital Multimeters (DMMs) ISL78234EVAL1Z, and ISL78235EVAL1Z have a default 33nF on the board for a ~10ms soft-start time. 500MHz quad-trace oscilloscope Signal generator for EN and/or SYNC pins Control Switches for EN and SYNC The evaluation board contain switches SW1 and SW2 for control Quick Setup Guide of the EN and SYNC pin. Table 1 details this function. 1. Ensure that the circuit is correctly connected to the supply and TABLE 1. SWITCH SETTINGS loads prior to applying any power. SW1 ENABLE FUNCTION 2. Connect the bias supply to V , the plus terminal to V (P4) IN IN and the negative return to PGND (P5). 1 (LEFT) OFF DISABLE IC 3. Connect the output load to V , the plus terminal to VOUT OUT 3 (RIGHT) ON ENABLE IC (P3) and the negative return to PGND (P7). 4. Verify that SW2 is in the proper position for PFM or PWM. SW2 SYNC FUNCTION 5. Verify that the position is ON for SW1. 6. Turn on the power supply and set for 2.7V to 5.0V. 1 (LEFT) PFM Skip mode at light load 7. Verify the output voltage is 1.8V for V . OUT 3 (RIGHT) PWM Fixed PWM frequency at light load Evaluating Other Output Voltages The ISL78233EVAL1Z, ISL78234EVAL1Z, and ISL78235EVAL1Z Power Inductor evaluation board outputs are preset to 1.8V for V . The output OUT The evaluation board contains a 0.68H output power inductor. It voltage can be adjusted from 0.8V to 3.3V. The output voltage has a 13.5A saturation current that is able to handle the peak , depends on the desired output voltage programming resistor, R 1 current limit of the IC. The inductor is chosen to optimize of the regulator. It is recommended to have R set to 100k. The 2 performance for V = 5V, V = 1.8V at 2MHz switching IN OUT value for R is typically between 66k and 450k, as shown in 1 frequency for up to 5A output currents. Equation 1. Internal vs External Compensation (EQ. 1) R = RVO VFB 1 1 2 The ISL78233, ISL78234 and ISL78235 feature an internal compensation network on the output of the error amplifier. The For faster transient response performance, add 10pF to 22pF in internal compensation simplifies design by reducing external parallel to R . Check loop compensation analysis to ensure 1 components while stabilizing the regulator under transient load optimum performance before use of capacitance. response. To use internal compensation network, tie the COMP pin to VDD. Frequency Control The restriction of an internal compensation network is that it The ISL78233, ISL78234, and ISL78235 have an FS pin that does not provide flexibility to optimize the compensation network controls the frequency of operation. Programmable frequency for conditions when additional output capacitance is needed to allows for optimization between efficiency and external minimize output overshoot from fast transient loading. The component size. Default switching frequency is 2MHz when FS is added capacitance affects the stability and response of the tied to V (R =0 and R is open). By removing R and IN 11 12 11 feedback loop. The internal compensation network is well suited changing the value of R , the switching frequency can be 12 for a wide range of switching frequencies and load di/dt changed from 500kHz to 4MHz according to Equation 2: transients, however, if the feedback network needs to be better 3 220 10 optimized for the application, external compensation should be ------------------------------ (EQ. 2) Rk = 14 T f kHz OSC used. When the COMP pin is not connected to VDD, an RC network from COMP pin to GND is used to provide the external Please refer to the ISL78235, ISL78233, ISL78234 datasheets compensation. for more details. For more information on the specification of the internal Soft-Start Control compensation network and designing for stability, refer to ISL78235, ISL78233, ISL78234 datasheets for more details. The ISL78233, ISL78234, and ISL78235 have an SS pin that controls the soft-start up time. Short SS pin to SGND for internal soft-start (approximately 1ms). Populate a capacitor, C , to SS adjust the soft-start time. This capacitor, along with an internal UG015 Rev 2.00 Page 2 of 9 October 26, 2016