rev. page date page date description: half-brick dc-dc converter 1 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w features 37.5-75w isolated output efficiency to 85% 300 khz switching frequency regulated output continuous short circuit protection industry standard half-brick size remote on/off over-temperature protection over-current protection description the vhb75w series of dc-dc converters are designed for high reliability applications, featuring over-temperature protection, over-current protection. the wide 4:1 input range (9-36v or 18-75v) is very useful to stabilize an input source like batteries in various discharging and charging conditions. additionally, high efficiency, fast response, tight regulations, remote sense and remote on/off control make these converters very useful in many applications. model input voltage output output input current efficiency nominal range voltage current 1 no load 2 full load 2 typ. 3 (v dc) (v dc) (v dc) (a) (ma) (ma) (%) vhb75w-q24-s3r3 24 9.0~36.0 3.3 15 50 2611 79 vhb75w-q24-s5 24 9.0~36.0 5 15 50 3811 82 vhb75w-q24-s12 24 9.0~36.0 12 6.25 50 3765 83 vhb75w-q24-s15 24 9.0~36.0 15 5 50 3720 84 vhb75w-q24-s24 24 9.0~36.0 24 3.12 50 3720 84 VHB75W-Q24-S48 24 9.0~36.0 48 1.56 50 3811 82 vhb75w-q48-s3r3 48 18.0~75.0 3.3 15 50 1320 80 vhb75w-q48-s5 48 18.0~75.0 5 15 50 1905 83 vhb75w-q48-s12 48 18.0~75.0 12 6.25 50 1860 84 vhb75w-q48-s15 48 18.0~75.0 15 5 50 1860 85 vhb75w-q48-s24 48 18.0~75.0 24 3.12 50 1860 85 vhb75w-q48-s48 48 18.0~75.0 48 1.56 50 1860 84 notes: 1. see output derating (page 4) 2. input currents are measured at nominal input voltage 3. efficiency is measured at nominal line, full load *v-infinity reserves the right to make changes to its products or to discontinue any product or service without notice, and to advise customers to verify the most up-to- date product information before placing orders. v-infinity assumes no liability or responsibility for customer?s applications u sing v-infinity products other than repair or replacing (at v-i?s option) v-infinity products not meeting v-i?s published specifications. nothing will be covered outside of standard product warranty. input parameter conditions/description min nom max units input voltage range 9 24 36 v dc 18 48 75 v dc under voltage lockout 24 vin power up 8.8 v dc 24 vin power down 8 v dc 48 vin power up 17 v dc 48 vin power down 16 v dc remote on/off control 4 section 15 in the application notes input filter pi type notes: 4. add suffix ?n? to the model number for negative logic on/off control
page date description: half-brick dc-dc converter 2 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w output parameter conditions/description min nom max units voltage accuracy 1 % transient response 25% step load change <500 sec external trim adj. range 10 % ripple & noise (20mhz bw) 3.3v, 5v 40 mv rms 100 mv p-p 12v& 15v 60 mv rms 150 mv p-p 24v 100 mv rms 240 mv p-p 48v 200 mv rms 480 mv p-p temperature coefficient 0.03 %/c short circuit protection continuous line regulation 5 0.2 % load regulation 6 0.2 % over voltage protection trip range, % vo nom. 115 140 % over current protection % nominal output current 110 160 % general specifications parameter conditions/description min nom max units switching frequency 300 khz operating ambient temp. 7 -40 100 c storage temperature -55 105 c thermal shutdown case temp. 100 c case material aluminum isolation specifications parameter conditions/description min nom max units isolation voltage input/output 1500 v dc input/case 1500 v dc output/case 1500 v dc isolation resistance 100 m notes: 5. measured from high line to low line at full load 6. measured from full load to zero load at nominal input 7. see output derating curve (page 4) *v-infinity reserves the right to make changes to its products or to discontinue any product or service without notice, and to advise customers to verify the most up-to- date product information before placing orders. v-infinity assumes no liability or responsibility for customer?s applications u sing v-infinity products other than repair or replacing (at v-i?s option) v-infinity products not meeting v-i?s published specifications. nothing will be covered outside of standard product warranty.
page date description: half-brick dc-dc converter 3 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w mechanical drawing
page date description: half-brick dc-dc converter 4 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w application notes 1. output de-rating the operating case temperature range for vhb75w is -40 ~ +100c. when operating the vhb75w series, proper derating or cooling is needed. the maximum case temperature under any operating condition should not exceed 100c. figure 1. output derating (forced convection with no heat sink) example: what is the minimum airflow necessary for a vhb75w-q48-s12 operating at nominal line, an output current of 6.25 a, and a maximum ambient temperature of 40c? solution: given: vin=48 v dc, vo=12 v dc, io=6.25 a determine power dissipation (pd): pd=pi-po=po(1- )/ pd=126.25(1-0.84)/0.84=14.29 w determine airflow: given: pd=14.29 w and ta=40c check above power de-rating curve: minimum airflow= 400 ft./min. verifying: the maximum temp. rise t = pd rca=14.293.64=52.02c. the maximum case temperature tc=ta+ t=92.02c<100c where: the rca is thermal resistance from case to ambience.the ta is ambient temperature and the tc is case temperature. power dissipated vs ambient temperature and air flo w ambient temperature ,ta(deg. c) power disspated ,pd(watts) natural convection 20 ft./min. (0.1 m/s) 100 ft./min. (0.5 m/s) 200 ft./min. (1.0 m/s) 300 ft./min. (1.5 m/s) 400 ft./min. (2.0 m/s) 500 ft./min. (2.5 m/s) 600 ft./min. (3.0 m/s) 700 ft./min. (3.5 m/s) 800 ft./min. (4.0 m/s) chart of thermal resistance vs air flow air flow rate typical rca natural convection 20ft./min. (0.1m/s) 7.12 /w 100 ft./min. (0.5m/s) 6.21 /w 200 ft./min. (1.0m/s) 5.17 /w 300 ft./min. (1.5m/s) 4.29 /w 400 ft./min. (2.0m/s) 3.64 /w 500 ft./min. (2.5m/s) 2.96 /w 600 ft./min. (3.0m/s) 2.53 /w 700 ft./min. (3.5m/s) 2.37 /w 800 ft./min. (4.0m/s) 2.19 /w
page date description: half-brick dc-dc converter 5 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w 2. input voltage range it is important to ensure the input voltage measured at the converter input pins is within the range for that converter. make sure wire losses and voltage ripples are accounted for. one possible problem is driving the converter with a linear unregulated power su pply. for example, if the average voltage measured by a dmm is 9v, with a voltage ripple of 3vpp, the actual input can swing from 7.5 v to 10.5v. this will be outside the specified input range of 9-36v and the converter may not function properly. on the other end, make sure the actual input voltage does not exceed the highest voltage of 36v or 75v. 3. lead wires make sure the input and output wires are of adequate awg size to minimize voltage drop, and ensure the voltage across the input terminals is above the converter's rated minimum voltage at all times. it is recommended to have the wire pairs twisted, respe ctively for the input pair and the output pair, so as to minimize noise pickup. 4. input current the input voltage source must be able to provide enough current to the converter, otherwise it may not start up or operate prop erly. a typical symptom is not starting or unusually low output voltage. in general, it is recommended to be able to provide at least: ipeak = 150%*pout/( *vmin) where pout is the maximum output power, vmin is the minimum input voltage and is the converter's efficiency. as an example, for vhb75w-q24-s5 to operate with 9~36 v input, 75 w output and an efficiency of 82%, the minimum source current is recommended to be: ipeak = 150% * 75 / (82% * 9) = 15.24 a . 5. input fuse to limit the input current and to facilitate input reversal protection and input ovp protection, a fast-acting input fuse is rec ommended for the input line. the fuse rating will depend on the input range and should allow for the maximum current at the lowest inpu t volt- age, as shown in this equation: ipeak = 150%*pout/( *vmin) . in the previous example of vhb75w-q24-s5, the peak input current at 9v was calculated to be 15.24 a. a 20 a fuse may be suitable for this application. make sure the fuse voltage rating is higher than the maximum input voltage. 6. remote sense the converter provides regulated outputs at the output terminals. when there is a large current and/or the output cable is of s ome length, the voltage at the end of the output cable may be noticeably lower than at the terminals. the converter can compensate up to 0.5v of voltage drop through remote sense terminals. to ensure accurate regulation, run two separate wires (twisted) from the desired regulation points to the remote sense terminals, as shown below. even if the load current is low, still connect +vo to +s and -vo to -s. +vo +s trim -s -vo (-) (+) load figure 2. remote sense
page date description: half-brick dc-dc converter 6 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w 7. output trimming (optional) the output voltages are preset to nominal values as indicated by the models table at the factory. if desired, the output volta ge may optionally be trimmed to a different value (+/- 10%) with external resistors and/or potentiometer as shown below. to trim the output voltage with fixed resistors, the output voltage can be calculated as follows. trim-up trim-down figure 4: trim-up voltage setup figure 5: trim-down voltage setup the value of r trim-up is defined as: the value of r trim-down is defined as: where: r trim-up is the external resistor in k . v o,nom is the where: r trim-down is the external resistor in k . v o,nom is the nominal output voltage. v o is the desired output voltage. r 1 , nominal output voltage. v o is the desired output voltage. r 1 , r 2 , r 3 , v r , and v f are internal to the unit and are defined in r 2 , and v r are internal to the unit and are defined in table 1. for example, to trim-up the output voltage of 5.0v table 1. for example, to trim-up the output voltage of 5.0v module (vhb75w-q48-s5) by 8% to 5.4v, r trim-up is calculated module (vhb75w-q48-s5) by 8% to 4.6v, r trim-down is calculated as follows: as follows: r load 10k trimpot +vin -vin -vo -s trim +s +vo figure 3. trimming with external potentiometer r load r trim-up +vin -vin +vo trim -vo r load +vin -vin +vo trim -vo r trim-down r2 = 8.2 k r1 = 5.8 k o o, nom = 5.4 - 5.0 = 0.4 v v - v = = 6.3 (k ) r 0.4 trim-up 5.8 - 8.2 x 0.4 v - v = = 3.98 (k ) r 0.4 trim-down 5.8 - 10.52 x 0.4 r2 = 10.52 k r1 = 5.8 k o o, nom = 5.0 - 4.6 = 0.4 v = (k ) r o o, nom v - v o o, nom trim-up r1 - r2 x (v - v ) = (k ) r o o, nom v - v o o, nom trim-down r1 - r2 x (v - v ) 13.0476 74.514 48v 16.67 14.76 13.304 8.2 7.2 42.33 25.474 19.656 5.8 3.168 24v 15v 12v 5v 3.3v table 1 295.527 1569.6 48v 120 94 60.1 10.52 15 430 150 86.45 5.8 6.18 24v 15v 12v 5v 3.3v table 2
page date description: half-brick dc-dc converter 7 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w 8. output ocp and short-circuit protection output overload and short circuit conditional will cause the output voltage to decline or shutdown altogether. if the case te mperature is not over 100c, the output recovers automatically when the short or ocp conditions are removed. in the case of slight overlo ading, the output voltage may not shut down, but the converter may build up heat over time, causing over-temperature shutdown. 9. over-temperature protection when the case temperature reaches about 100c, the converter's built-in protection circuit will shut down the output. when the tem- perature is reduced enough to a safe operating level, the converter will recover to normal operations automatically. 10. output ovp in case the output voltage exceeds the ovp threshold, the converter shuts down. 11. output parallel connections the converter is not designed for load share on the output. one may be inclined to use this circuit to force current sharing b y trim- ming the output voltages for each converter. however, this circuit may not reliably or accurately divide the load current, as the device characteristics of the converters or the diodes may not be balanced over a range of operating conditions. we generally do not recom- mend this circuit to increase power output over a single converter. instead, we recommend this setup for redundancy only, havi ng one converter as a backup in case of a failure. make sure the or-ing diodes can handle the voltage and full load current. +vin -vin +vo -vo +vin -vin +vo -vo figure 6. output parallel connections
page date description: half-brick dc-dc converter 8 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w 12. output series connections two or more converters can be connected in series to obtain a higher output voltage. to prevent output reverse biasing each ot her in case of a short, add a schottky diode on each output in reverse polarity, as shown in the diagram. in the event of a short, th e con- verters will forward-bias the diodes and the output reversal will be limited to one diode drop (about 0.5v) only, so as not to damage the converters. the forward current will cause each converter to go into short-circuit protection. for proper diode selectio n, make sure that: 1) the diodes voltage rating is higher than each converter output; 2) the rated diode current can carry the short-ci rcuit cur- rent; 3) the diodes do not overheat before the short is removed. 13. remote output on/off control the converter output can be enabled or disabled through the on/off pin. the control logic is shown in this table. a common con trol circuit is shown below. the standard version defaults to positive logic. for negative logic, indicate the selection when orderi ng. 14. isolation the input and output of the converter are electrically isolated. if needed, an output terminal can be connected to an input te rminal, resulting in the converter non-isolated. +vin -vin +vo -vo +vin -vin +vo -vo figure 7. output series connections logic table negative logic positive logic sw closed (v <0.8 v) output on output off sw open (v >2.4 v) output off output on rem rem sw high signal here disable output -vin (pin 4) rem (pin 2) rem -vin sw rem -vin -vo +vo figure 8. remote on/off control figure 9. remote on/off control with transistor switch
page date description: half-brick dc-dc converter 9 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w 15. input filtering and emi interference the vhb75w converters have input capacitors that control input current ripple and the associated emi interference. however, it has not been tested to a formal standard for conducted emissions. additional filtering may be needed to ensure compliance to a n emi standard. refer to figure 10 for a reference circuit. v-infinity offers a line of dc input filter modules designed to help reduce common and differential mode noise. the table belo w provides a list of dc-dc converter models within the series and the mating dc input filter. note: the recommended components are a starting point but not guaranteed for meeting these emi requirements. more or less filtering may be required for a specific application or to meet other emi standards, e.g.mil-std-461 c4 case +vo -vo +vin -vin l2 c3 c2 emi to meet class a vhb75w series c2 c3 c4 l2 47f/50v esr<0.60 47f/50v esr<0.60 2200pf/2kv 2.5h emi to meet class b 220f/50v esr<0.120 220f/50v esr<0.120 2200pf/2kv 1.5h figure 10. emi filter for vhb75w series mating filter module notes vhb75w-q24-sxx vfm-10a vhb75w-q48-sxx vfm-10a
16. output filtering the converter has built-in capacitors at the output to control ripple and noise. if desired, additional output capacitance can be introduced at the input to the powered equipment. recommended starting point: one 10 f tantalum and one 1 f ceramic capacitor in parallel at the output. 17. output noise measurement schematic for proper output ripple and noise measurement, connect a 10 f tantalum and a 1 f ceramic capacitor across the output. set the scope bandwidth to 20mhz. probe directly off of one of the capacitors, using a small ground clip to minimize measurement error . page date description: half-brick dc-dc converter 10 of 10 04/2011 20050 sw 112 th ave. tualatin, oregon 97062 p h o n e phone 503.612.2300 f a x www.v-infinity.com fax 503.612.2383 part number: vhb75w resistor load to scope solid tantalum 10f ceramic 1.0f +vin -vin -vo -s trim +s + +vo figure 11. output noise measurement circuit
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