rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 1 http://www.richtek.com rt 7252bzsp evaluation board purpose the rt7252b is a high - efficiency current mode synchronous step - down regulator that can deliver up to 2a output current from a wide input voltage range of 4v to 17v. this document explains the function and use of the rt7252b evaluation board (evb) and provides information to enable operation and modification of the evaluation board and circuit to suit individual requirements. . table of contents purpose ................................ ................................ ................................ ................................ ................................ ................ 1 introduction ................................ ................................ ................................ ................................ ................................ ...... 2 key performance summ ary table ................................ ................................ ................................ ................................ ... 2 bench test setup con ditions ................................ ................................ ................................ ................................ ............ 3 sc hematic, bill of mat erials & board layou t ................................ ................................ ................................ ............... 5 more information ................................ ................................ ................................ ................................ ........................... 10 important notice for richtek reference de signs ................................ ................................ ................................ ...... 10 y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 2 http://www.richtek.com introduction general product information the rt7252b is a high efficiency, monolithic synchronous step - down dc/dc converter that operates at 800k hz and delivers up to 2a output current from a 4v to 17v input supply. the rt7252b s current mode architecture allows the transient response to be optimized . cycle - by - cycle current limit provides protection against shorted outputs and soft - start eliminates input current surge during start - up. fault conditions also include output under voltage protection, output over voltage protection, and thermal shutdown. t he low current (<5a) shutdown mode provides output disconnect, enabling easy power management in battery - powered systems. the rt7252b is available in a sop - 8 (exposed pad) package product feature ? 4v to 17v input voltage range ? 2a output current ? internal n - mosfets ? current mode control ? fixed frequency operation : 800khz ? output adjustable from 0.8v to 12v ? up to 95% efficiency ? internal compensation ? stable with low esr ceramic output capacitors ? cycle - by - cycle over current protection ? input under voltage lockout ? output under voltage protection ? output over voltage protection ? power good indicator ? thermal shutdown protection ? rohs compliant and halogen free key performance summary table key f eatures evaluation b oard n umber: pcb00 8 _v1 default input voltage 12v max output current 2a default output voltage 3.3v default marking & package type RT7252BZSP ( sop - 8 (exposed pad) ) operation frequency steady 800k hz at pwm other key features 4v to 17v input voltage range power good indicator protection over current protection hiccup mode output under - voltage & over - voltage protection thermal shutdown y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 3 http://www.richtek.com bench test setup conditions headers description and placement please carefully inspect the evb ic and external components, comparing them to the following bill of materials, to ensure tha t all components are installed and undamaged. if any components are missing or damaged during transportation, please contact the di stributor or send e - mail to evb_service@richtek.com test points the evb is provided with the test points and pin names listed in the table below. test point/ pin name signal comment (expected waveforms or volt age levels on test points) vin input voltage input voltage range= 4v to 17v vout output voltage default output voltage = 3.3v output voltage range= 0.8v to 12v (see output voltage setting section for changing output voltage level) sw switching nod e test point sw waveform en enable test point enable signal. en is automatically pulled high (by r4) to enable operation. connect en low to disable operation. bs boot strap supply test point floating supply voltage for the high - side n - mosfet switch pg power good test point power good indicator v1 external voltage for pg external voltage terminal for pg pull - up voltage. gnd ground ground power - up & measurement procedure 1. apply a 12v nominal input power supply (4v < v in < 17v) to the vin and gnd terminals. 2. the en voltage is pulled to logic high by r4 (100k to vin) to enable operation. drive en high (>2.5v) to enable operation or low (<0.4v) to disable operation. 3. verify the output voltage (approximately 3.3v) between vout and gnd. 4. connect an external load up to 2a to the vout and gnd terminals and verify the output voltage and current. y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 4 http://www.richtek.com output voltage setting set the output voltage with the resistive divider (r1, r2) between vout and gnd with the midpoint connected to fb. th e output is set by the following formula: the installed v out capacitors (c4, c5) are 22 f, 16 v x5r ceramic types. do not exceed their operating voltage range and consider their voltage coefficient (cap acitance vs. bias voltage) and ensure that the capacitance is sufficient to maintain stability and provide sufficient transient response for your application. this can be verified by checking the output transient response as described in the rt7252 ic data sheet. y o u r p o w e r p a r t n e r . out r1 v = 0.8 x (1 + ) r2
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 5 http://www.richtek.com schematic, bill of materials & board layout evb schematic diagram c1, c2: 10f/50v/x5r, 1206, tdk c3216x5r1h106k c4, c5: 22f/16v/x5r, 1210, murata grm32er61c226k l1: 6.8h taiyo yuden nr8040t6r8n, dcr=25m y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 6 http://www.richtek.com bill of materials reference qty part number description package manufacture u1 1 RT7252BZSP dc - dc converter sop - 8 (exposed pad) r ichtek c1, c2 2 c3216x5r1h106k160ab 10 f/10%/50v/x5r ceramic capacitor 1206 tdk c4, c5 2 grm32er61c226ke20# 22 f/10%/16v/x5r ceramic capacitor 1210 murata c7 1 grm32mr71h103ka01# 10nf/10%/50v/x7r ceramic capacitor 0 603 murata c3, c6 2 c1608x7r1h104k080aa 0.1 f/10%/50v/x7r ceramic capacitor 0 603 tdk c8, c9, c10 0 not installed 0 603 l1 1 nr8040t6r8n 6.8uh/3.7a/30%, dcr=25m, inductor 8mmx8mmx4mm taiyo yuden r1 1 47 k/1%, resistor 0 603 r2 1 15 k/1%, resistor 0 603 r3, r4 1 100k/1%, resistor 0 603 cp1 1 short d3, r6 0 not installed tp 4 test pin gp 6 golden pin y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 7 http://www.richtek.com evb layout top view (1 st layer) bottom view (4 th layer) y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 8 http://www.richtek.com component placement guide component side (1 st la yer) pcb layout component side (1 st layer) y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 9 http://www.richtek.com pcb layout bottom side (4 th layer) y o u r p o w e r p a r t n e r .
rt 7252bzsp evaluation board ug 7252bzsp - 00 january 2015 10 http://www.richtek.com more information for more information, please find the related datasheet or application notes from rich t ek website http://www. richtek .com . important notice for richtek reference designs this document is for reference only, nothing contained in this document shall be construed as richteks warranty, express or implied, under contract, tort or statutory, with respect to the presentation herein. in no event shall richtek be liable to buyer or user for any and all damages including without limitation to direct, indirect, special, punitive or consequential damages. y o u r p o w e r p a r t n e r .
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