44 ics 1-1-3 dc/dc converter ics electrical characteristics unit v mv/ ? % khz mv mv a ma a a v a v % nsec ?? 1 b s b n f u f s reference voltage temperature coefficient of reference voltage efficiency oscillation frequency line regulation load regulation overcurrent protection starting current quiescent circuit current 1 quiescent circuit current 2 ss pin outflow current at low voltage open voltage en pin inflow current on threshold voltage maximum on duty minimum on time thermal protection start temperature thermal protection return hysteresis (ta=25 c, v in =12v, v o =3.3v, and io=1.0a, unless otherwise specified) ratings min. typ. max. 0.784 0.800 0.816 0.05 90 400 500 600 50 50 3.1 6.0 6 10 61 01 4 3.0 50 100 0.7 1.4 2.1 90 150 151 165 20 *: pin 8 is the ss pin. soft start at power on can be performed with a capacitor connected to this pin. the ss pin is pulled up to the power supply in the ic, so applying the external voltage is prohibited. $ p o e j u j p o t 5 b C ? u p ? 7 * / 7 u p 7 * p u p " 7 & / ? q v m m v q u p 7 * / * p "
7 & / 7 7 4 4 7 7 & / 7 ss y 4 p g u t u b s u 8 c9 NR887D full-mold, separate excitation step-down switching mode regulator ics NR887D features ? dip 8 pin package ? input voltage range (v in ): v o + 3 to 18 v ? synchronous rectifier mode ? high efficiency: 90% ? introduction of current mode control method ? a ceramic capacitor can be used for output ? built-in phase correction component ? output current: 2 a ? reference voltage and accuracy of 0.8 v 2% ? oscillation frequency: 500 khz ? output on/off available ? undervoltage lockout ? soft start function applications ? power supply for lcdtv and pdp ? power supply for dvd, bd, and stb ? on-board local power supply ? power supply for switches current mode control, synchronous rectifier step-down switching mode absolute maximum ratings recommended operating conditions unit v w c c c/w c/w ratings 20 1.50 C40 to +150 C40 to +150 25 67 symbol v in p d t j t stg j-c j-a parameter conditions input voltage power dissipation junction temperature storage temperature thermal resistance (junction to lead (4 pins)) thermal resistance (junction to ambient air) when mounted on a 70 60 mm glass-epoxy board (with a 1310 mm 2 copper area) when mounted on a 70 60 mm glass-epoxy board (with a 1310 mm 2 copper area) unit v a v c ratings 4.5 or v o + 3* to 18 0 u p 2.0 0.8 to 14 C40 to +85 4 z n c p m 7 * / * p 7 p 5 p q parameter input voltage range output current range output voltage range operating temperature range *: the minimum value of the input voltage range is 4.5 v or v o + 3 v, whichever is higher. 4 z n c p m 7 3 & ' ? 7 3 & ' ? 5 g p 7 - * / & 7 - p b e * t * * / * * / p g g
* & / 4 4 7 4 4 ) * & / 7 $ & ) % . " 9 % . * / 5 4 % 5 4 % @ i z t downloaded from: http:///
45 ics external dimensions (dip8) pin assignmentq bs w v in e sw r gnd t fb y nc u en i ss plastic mold package typeflammability: ul 94v-0 product mass: approx. 0.49g (unit : mm) block diagram t ypical connection diagram c1, c2: 10 f/25v c4, c5: 22 f/16v c9: 0.1 f c10: 0.1 f l1: 10 h r3: 20
to 47
r4+r5: 5k
y y (v o =3.3v) r6: 1.6k
76 4 en 3.5v 5v 0.8v 3.5v 0.8v 5v error amp 10ua nc gnd on/ off osc ocp + ++ - - current sense pwm logic ss fb sw bs in ss 8 5 3 1 2 compensation drive reg p. reg vref tsd uvlo NR887D vin c1 c9 7 21 35 r3 l1 r4r5 r6 option d1 c4 c5 v out bs vin sw fb ss en nc gnd c10 8 46 c2 NR887D 7 8 2 1 54 63 9.4 0.3 0.5 0.1 0 to 15 6.5 0.2 3.4 0.1 3.3 0.2 4.2 0.3 7.5 0.5 1.0 +0.3 - 0.05 1.5 +0.3 - 0.05 0.25 +0.1 - 0 .05 2.54 7.6 0.25 m 0.89 typ downloaded from: http:///
|
