NJM2345 - 1 - ver.2009-10-19 pwm dc/dc converter ic with standby function general description package outline features operating voltage 3.0v to 40v wide oscillator frequency 1khz to 150khz ? maximum duty ratio 100% ? precision reference voltage v th =1.25v 1% internal high power transistor 1.5a max. internal over current limit circuit pwm switching control standby function 9 a typ. bipolar technology package outline NJM2345d : dip8 NJM2345m : dmp8 pin configuration block diagram NJM2345d NJM2345m pin function 1. c s 2. e s 3. c t 4. gnd 5. in- 6. v + 7. on/off 8. s i NJM2345d NJM2345m 1 8 2 7 3 6 4 5 the NJM2345 is a step down pwm dc/dc converter ic. an internal 1.5a power transistor, a pulse-by pulse current limi t circuit and a 1% precision reference make the NJM2345 suitabl e for a wide range of voltage converter needs. the NJM2345 features a standby function that can be used fo r both power saving and safety operation. 1 1.5a 4 3 2 8 5 6 7 v + e s gnd pwm logic r s q vref 1.25v s i c t c s on/off high :on low :off (standby) in- 300mv ipk sense pwm comp error amp 160 ? %
NJM2345 - 2 - ver.2009-10-19 absolute maximum ratings (ta=25c) parameter symbol maximum ratings unit maximum supply voltage v + 40 v comparator input voltage v ir -0.3 ~ 40 (note) v on/off terminal voltage v on/off -0.3 ~ 40 (note) output switch voltage v sw 40 v output switch current i sw 1.5 a power dissipation p d dip8 dmp8 875 580 (*1) 750 (*2) mw operating temperature range topr -40 ~ +85 c storage temperature range tstg -50 ~ +150 c (note) when supply voltage is less than 40v, the abso lute maximum input voltage is equal to the supply voltage. (*1) at on pc board : 114.3mm 76.2mm 1.6mm(2 layer fr-4) : conform to eia/jedec (*2) at on pc board : 114.3mm 76.2mm 1.6mm(4 layer fr-4) : conform to eia/jedec power dissipation vs. ambient temperature 0 200 400 600 800 1000 0255075100 ambient temperature ta ( o c) power dissipation p d (mw) power dissipation vs. ambient temperature (topr=-40~+85 o c, tj= ~150 o c) dip8 dmp8 at on 4 layer pc board at on 2 layer pc board
NJM2345 - 3 - ver.2009-10-19 electrical characteristics dc characteristics (v + = v on/off =5v, ta=25 c) parameter symbol test conditions min. typ. max. unit oscillator block oscillation frequency f osc in-= v th -5v, c t =1nf 18 27 36 khz charge current i chg 11 18 27 a discharge current i dis 110 180 300 a voltage swing v osc c t =1nf ? 0.5 ? v p-p current limit peak current sense voltage v ipk 250 300 350 mv output switch saturation voltage v sat i sw =0.7a ? 1.0 1.3 v output transistor bias resistance r bias ? 160 ? ? collector off-state current i c(off) v ce =40v ? 0.01 1 a maximum duty ratio m ax d uty in-=0v 100 - - % error amplifier threshold voltage v th 1.2375 1.250 1.2625 v input bias current i ib in-= v th ? 100 200 na on/off block on threshold voltage v on 0.8 ? ? v off threshold voltage v off ? ? 0.56 v input bias current (on/off terminal) i on/off v on/off =5v ? 240 300 a general characteristics standby current i ccstby v on/off =0v ? 9 20 a operating current i cc c t =1nf, s i =v + , in- > v th , e s =gnd ? 2.8 4.0 ma (note) output switch tests are performed under pul sed conditions to minimize power dissipation.
NJM2345 - 4 - ver.2009-10-19 typical applications step-down converter though the i on/off decreases by inserting "r on/off " to between on/off terminal and v in terminal, the minimum operating voltage is increased due to the resister " r on/off ". d1 use to schottky diode. step-down converter (high current) though the i on/off decreases by inserting "r on/off " to between on/off terminal and v in terminal, the minimum operating voltage is increased due to the resister " r on/off ". d1 use to schottky diode. 1 NJM2345 43 2 c t 8 6 7 d1 r2 l1 5 r1 r sc c in c out v in v out c1 on/off control r on/off 1 NJM2345 43 2 c t f 8 6 7 5 r sc c in v in r be r bc d1 r2 l1 r1 c out v out c1 on/off control r on/off
NJM2345 - 5 - ver.2009-10-19 timing chart oscillator waveform error amp output switch output off on osc block to ff, nor high low ipk sense output high low
NJM2345 - 6 - ver.2009-10-19 typical characteristics 1 10 100 10 100 1000 10000 100000 oscillator frequency f osc (khz) oscillator frequency vs. timing capacitor (v + =5v, s i =v + , pin 5=gnd, ta=25 o c) timing capacitor c t (pf) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 saturation voltage vs. collector current (v + =5v, c s =c d , ta=25 o c) collector current i c (a) saturation voltage v sat1 (v) 0 100 200 300 400 500 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 input bias current vs. in- terminal voltage (v + =5v, ta=25 o c) in- terminal voltage (v) input bias current i ib (na) 0 1 2 3 4 010203040 operating current vs. operating voltage (c t =1nf, s i =v + , in->v th , es=gnd, ta=25 o c) operating voltage v + (v) operating current i cc (ma) 0 1 2 3 4 5 6 0.50.550.60.650.70.750.8 output voltage vs. on threshold voltage (v + =10v, vo=5v, io=150ma, ta=25 o c) on threshold voltage von (v) output voltage vo (v) rc=0 ? rc=100k ? rc=50k ?
NJM2345 - 7 - ver.2009-10-19 typical characteristics 0 150 300 450 600 012345678 on/off terminal voltage v on/off (v) on/off input bias current i on/off (ua) on/off input bias current vs. on/off terminal voltage (v + =10v, vo=5v, io=150ma, ta=25 o c) rc=0 ? rc=100k ? rc=50k ? 1.2 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 -50 -25 0 25 50 75 100 125 150 ambient temperature ta ( o c) threshold voltage v th (v) threshold voltage vs. temperature (v + =5v) 0.6 0.7 0.8 0.9 1 1.1 1.2 -50 -25 0 25 50 75 100 125 150 ambient temperature ta ( o c) saturation voltage v sat1 (v) saturation voltage vs. temperature (v + =5v, c s =c d , i sw =0.7a) 240 260 280 300 320 340 360 -50 -25 0 25 50 75 100 125 150 ambient temperature ta ( o c) current limit sense voltage v ipk (mv) current limit sense voltage vs. temperature (v + =5v) 0 1 2 3 4 5 -50 -25 0 25 50 75 100 125 150 ambient temperature ta ( o c) operating current i cc (ma) operating current vs. temperature (v + =5v, c t =1nf, s i =v + , in->v th , es=gnd)
NJM2345 - 8 - ver.2009-10-19 memo [caution] the specifications on this databook are only given for information , without any guarantee as regards either mistakes or omissions. the application circuits in this databook are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights.
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