150khz, 2a pwm buck dc/dc converter tj1509a features out p ut volta g e: 3.3v, 5v, 12v and ad j ustable output version ad j ustable version out p ut volta g e ran g e, 1.23v to 18v+4% 150khz +15% fixed switchin g fre q uenc y volta g e mode non-s y nchronous pwm control thermal-shutdown and current-limit p rotection on/off shutdown control in p u t o p eratin g volta g e can be u p to 26v out p ut load current: 2a sop-8l p acka g e s low p ower standb y mod e built-in switchin g transistor on chi p moisture sensitivit y level 3 application s sim p le hi g h-efficienc y ste p -down re g ulator on-card switchin g re g ulator s positive to ne g ative converter ne g ative ste p -u p converters ordering informatio n power su pp l y for batter y char g er s description mar. 2010 - r1.3 htc tj1509a 5.0 sop-8 pin description 4 pin no function description 1 vin operating voltage input 5~8 tj1509ad-adj tj1509a adj tj1509ad-3.3 tj1509a 3.3 TJ1509AD-12 tj1509a 12 tj1509ad-5.0 - 1 - 2 vout switching output 3 fb output voltage feedback control sd on/off shutdown ground ground device marking package the tj1509a series are monolithic ic designed for a step-down dc/dc converter, and own the ability of driving a 2a load without additional transistor component. due to reducing the number of external component, the board space can be saved easily. the external sh utdown function can be controlled by logic level and then come into standby mode. the internal compensation makes feedback control have good lin e and load regulation without external design. regarding protected function, thermal shutdown is to p revent over temperature operating from damage, and current limit is against over current operating of the output switch. if current limit function occurred and vfb is down to 0.5v below, the switching frequenc y will be reduced. the tj1509a series operates at a switching frequency of 150khz thus allowing smaller sized filter components than what would be needed with lower frequency swit ching regulators. other features include a guaranteed +4% tolerance on output voltage under spec ified input voltage and output load conditions, and +15% on the oscillator frequency. the output version included fixed 3.3v, 5v, 12v, and an adjust able type. the packages are available in a standard 8-lead sop-8 package. sop-8 pkg
150khz, 2a pwm buck dc/dc converter tj1509a t yp ical a pp lication circuit htc - 2 - tj1509a 3 1 2 4 5~8 tj1509a 3 1 2 4 5~8 tj1509a 3 1 2 4 5~8 c in 470uf/30v c in 470uf/30v d1 in5824 d1 in5824 d1 in5824 c o 220uf or 470uf/10v c o 220uf or 470uf/10v c o 220uf or 470uf/10v c in 470uf/30v
150khz, 2a pwm buck dc/dc converter tj1509a htc - 3 - block diagram 30
150khz, 2a pwm buck dc/dc converter tj1509a htc - 4 - tj1509a -adj tj1509a -3.3v tj1509a -12 v tj1509a -5.0v
150khz, 2a pwm buck dc/dc converter tj1509a htc - 5 - typical performance characteristics 4.92 4.93 4.94 4.95 4.96 4.97 4.98 4.99 0 0.5 1 1.5 iout[a] vout[v] 70.0 72.0 74.0 76.0 78.0 80.0 82.0 84.0 0 0.5 1 1.5 iout[a] efficiency[%] 4.92 4.93 4.94 4.95 4.96 4.97 4.98 0 0.5 1 1.5 iout[a] vout[v] 68.0 70.0 72.0 74.0 76.0 78.0 80.0 82.0 84.0 0 0.5 1 1.5 iout[a] efficiency[%] 3.00 3.50 4.00 4.50 5.00 5.50 2468101214 vin[v] iin[ma] 1.220 1.222 1.224 1.226 1.228 1.230 1.232 1.234 -40 -20 0 20 40 60 80 100 120 temp. [oc] v fb [v] tj1509a output voltage vs. output current (vin=12v, vout=5v, io=2a) tj1509a efficiency vs. output current (vin=12v, vout=5v, io=2a) tj1509a output voltage vs. output current (vin=15v, vout=5v, io=2a) tj1509a efficiency vs. output current (vin=15v, vout=5v, io=2a) tj1509a input current vs. input voltage (io=0a) tj1509a feedback voltage vs. temperature (vin=12v, vout=5v)
150khz, 2a pwm buck dc/dc converter tj1509a htc - 6 - typical performance characteristics tj1509a efficiency vs. temperature ( v in =12v, v out = 5v , i o= 2a) tj1509a efficiency vs. temperature ( v in =12v, v out = 3.3v , i o= 2a) tj1509a saturation voltage vs. temperature ( v cc =12v, v fb = 0v , vsd = 0) tj1509a switch current limit vs. temperature ( v cc =12v, v fb = 0v) tj1509a supply current vs. temperature ( v cc =12v, no load, von/off=0v(switch on), von/off=5v(switch off))
150khz, 2a pwm buck dc/dc converter tj1509a htc - 7 - typical performance characteristics tj1509a threshold voltage vs. temperature (vcc=12v, i o =100ma) tj1509a on/off current vs. on/off voltage (vin=12v) tj1509a feedback current vs. temperature (vcc=12v, vout=5v, vfb=1.3v) tj1509a frequency vs. temperature (vcc=12v, io=500ma, vout=5v) tj1509a output voltage vs. temperature (vin=12v, io=2a)
150khz, 2a pwm buck dc/dc converter tj1509a htc - 8 - function description pin functions +vin this is the positive input supply for the ic switching regulator. a suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. ground circuit ground. output internal switch. the voltage at this pin switches between (+vin ? vsat) and approximately ? 0.5v, with a duty cycle of approximately vout / vin. to minimize coupling to sensitive circuitry, the pc board copper area connected to this pin should be kept a minimum. feedback(fb) senses the regulated output voltage to complete the feedback loop. on/off (sd) allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 150ua. pulling this pin below a threshold voltage of approximately 1.3v turns the regulator on, and pulling this pin above 1.3v (up to a maximum of 18v) shuts the regulator down. if this shutdown feature is not needed, the sd pin can be wired to the ground pin or it can be left open, in either case the regulator will be in the on condition. thermal considerations the sop-8 package needs a heat sink under most conditions. the size of the heatsink depends on the input voltage, the output voltage, the load current and the ambient temperature. the tj1509a junction temperature rises above ambient temperature for a 3a load and different input and output voltages. the data for these curves was taken with the tj1509a (sop-8 package) operating as a buck-switching regulator in an ambient temperatur e of 25 (still air). these temperature rise numbers are all approximate and there are many factors that can affect these temperatures. higher ambient temperatures require more heat sinking. for the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. [once exception to this is the output (switch) pin, which should not have large areas of copper.] large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. package thermal resistance and junction temperature rise numbers are all approximate, and there are many factors that will affect these numbers. some of these factors include board size, shape, thickness, position, location, and even board temperature. other factors are, trace width, total printed circuit copper area, copper thickness, single or double-sided, multi-layer board and the amount of solder on the board. the effectiveness of the pc board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. furthermore, some of these components such as the catch diode will add heat to the pc board and the heat can vary as the input voltage changes. for the inductor, depending on the physical size, type of core material and the dc resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board.
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