QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 874 HOT SWAP CONTROLLER WITH 8-BIT ADC AND I2C INTERFACE LTC4215 DESCRIPTION Demonstration Circuit 874 showcases the LTC4215IUF The DC874 permits evaluating the LTC4215 during positive low voltage Hot Swap controller with I2C com- turn-on and turn-off transients as well as during steady patible monitoring in a 60W, 10.2 to 13.6V application. state conditions. Included on board is an input clamp, input and output Design files for this circuit board are available. Call voltage dividers for UV, OV, and PWRGD, LEDs to indi- the LTC factory. cate the presence of various voltages and signals and , LTC and Hot Swap are registered trademarks of Linear Technology Corpora- turret terminals for critical signals to facilitate evaluation tion. in a working system. Input and output connections are made by 93 mil turrets which if removed, accommodate insertion of up to 12 gauge wires for in-situ testing. An I2C port designed to interface with DC590A allows con- trol of DC874 with LTC s QuickEval software. Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Supply Voltage Rated operating limits 2.9V VCC 15V Under Voltage Lockout Transition to operating mode 2.75V V 2.89V DD(UVL) UV, OV, FB Pin Threshold Voltage 1.215V V 1.255V TH V = 2.9V to 15V DD Gate to Source Voltage 5.0V V 6.5V GS I =1uA GATE Gate Pull-Up current Charge Pump On, V 0.2V 15A I 30A GATE GATE Normal Gate Pull-Down Current ON Pin Signal Low 0.8mA I 1.3mA GATE Si4864DP and 4mW SENSE Resistor 5.4A I 7.1A LIMIT Circuit Breaker Voltage Si7880ADP and 1mW SENSE Resistor 22A I 28A LIMIT ADC Resolution (No missing codes) 8 VDD-Sense +/- 1.5 LSB ADC Offset SOURCE +/- 1 LSB ADIN +/- 1 LSB VDD-Sense 37.625mV V 39.275mV FS ADC Full-Scale Voltage (255 * V ) SOURCE 15.14 V 15.74 LSB FS ADIN 1.205 V 1.255 FS VDD-Sense +/- 5.5 LSB ADC Total Unadjusted Error SOURCE +/- 5 LSB ADIN +/- 5 LSB 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 874 HOT SWAP CONTROLLER WITH 8-BIT ADC AND I2C INTERFACE OPERATING PRINCIPLES The LTC4215 is a low voltage hot swap controller that current. The current limit and circuit breaker thresh- has a 2.9V to 15V operating range and a 24V absolute olds can be adjusted by changing the sense resistor, maximum operating voltage for the VDD pin. This RS. To enable demonstration of higher current appli- demo circuit is populated for +12V operation, but it cations up to 20A, provisions have been made to re- can easily be re-adjusted for any voltage between 2.9V place RS with a 1W, 2512 size sense resistor and re- and 15V by replacing R1, R2 and R7 (top resistors in place Q1 with a MOSFET in a PowerPAK SO-8, such as the UV/OV divider and the FB divider). The DC874 as the Si7880ADP. The large turrets may be removed to supplied by the factory is populated with a Si4864DP permit installation of up to 12 gauge wire for direct, MOSFET in an SO-8 package and a 4mW, 1/2W, cur- low resistance connections to the board. None of the rent sense resistor, providing a minimum of 5.4A load turrets are swaged. QUICK START PROCEDURE Demonstration circuit 874 is easy to set up to evaluate the performance of the LTC4215. Refer to Figure 4 for proper measurement equipment setup and follow the procedure below: 1. The DC874 is factory setup to operate in a 12 volt Alternately, for low power applications, Q1 may be system at current levels up to 5 amps. If the replaced with a MOSFET in a SSOT-6 package using LTC4215 is to be evaluated at a different operating alternate pads on the back of the board. condition, follow 2-6 below, otherwise skip to 6. 6. The TIMER SELECT jumper can be used to choose 2. If evaluating at a voltage other than 12V, R1 and R2 between the external timer capacitor, CT, and the must be adjusted for proper UV and OV PIN re- built in internal startup time of 100ms. CT is stuffed sponse. Select with a 0.68uF capacitor at the factory, which pro- R2=V /V 13.7K*1.235/1.205-13.7K, and R1= vides an 8ms startup time. To customize the startup MAX MIN V *(13.7k+R2)/1.205-13.7-R2, where V and time, select CT=T /12.3(ms/uF)+10*CSS. MIN MIN START V are the minimum and maximum output volt- MAX 7. The soft start capacitor, CSS, sets the ramp rate at ages expected for normal operation. which the inrush current will increase when turning 3. If evaluating at a voltage other than 12V, R7 must be on. CSS is stuffed with a 68nF capacitor at the fac- adjusted for proper foldback and power-good detec- tory, which provides a 5mV/ms inrush sense voltage tion. Select R7= V *3.01k/1.235-3.01k, where ramp. CSS has a minimum value of 1nF. CT must MIN V is the minimum output voltage value for which be at least 10 times CSS to avoid a condition where MIN power is determined to be good. the startup timer expires before the inrush ramp al- lows the MOSFET to turn on. 4. If the DC874 will operate at other than 5Amps max, change the value of R =0.9922mV/I 8. The LTC4215 does not require an RC network on the SENSE LOAD(MAX) for a 1% tolerance current sense resistor. GATE pin for compensation. However, an RC net- work may be used to limit the rate at which the 5. If the DC874 will be operating above 10Amps, re- GATE rises to provide an inrush current below the place Q1 with a suitable PowerPAK SO-8 package internal current limit. Pads R6 and CG on the back MOSFET such as the Si7880ADP suitable for up to of the board are available for this purpose. R6 and 20Amps. The SO-8 pads on the front of the board include the extra heat-sinking this package requires. 2