uc1838a uc2838a uc3838a magnetic amplifier controller features independent 1% reference two uncommitted, identical operational amplifiers 100ma reset current source with C120v capability 5v to 40v analog operation 5w dil package 10 vcc vref 9 2.5v reference inv. in 8 e/a out 3 inv. in 6 7 n.i. in 2 1 n.i. in c/l out c/l e/a 3.5v 15 dr 1 16 dr 2 reset 14 vm 11 5 12 13 4 gnd gnd gnd gnd 20 1k 5k block diagram 04/99 udg-97174 description the uc1838a family of magnetic amplifier controllers contains the circuitry to gen- erate and amplify a low-level analog error signal along with a high volt- age-compliant current source. this source will provide the reset current necessary to enable a magnetic amplifier to regulate and control a power supply output in the range of 2a to 20a. by controlling the reset current to a magnetic amplifier, this device will define the amount of volt-seconds the magnetic amplifier will block before switching to the conducting state. magnetic amplifiers are ideal for post-regulators for multi- ple-output power supplies where each output can be independently controlled with efficiencies up to 99%. with a square or pulse-width-modulated input voltage, a magnetic amplifier will block a portion of this input waveform, allowing just enough to pass to provide a regulated output. with the uc1838a, only the magnetic ampli- fier coil, three diodes, and an output l-c filter are necessary to implement a com- plete closed-loop regulator. the uc1838a contains a precision 2.5v reference, two uncommitted high-gain op amps and a high-gain pnp-equivalent current source which can deliver up to 100ma of magnetic amplifier reset current and with C120 volt capability. these devices are available in a plastic bat-wing dip for operation over a C20c to +85c temperature range and, with reduced power, in a hermetically sealed cerdip for C55c to +125c operation. surface mount versions are also available. this improved a version replaced the non a version formerly introduced.
2 uc1838a uc2838a uc3838a absolute maximum ratings supply voltage, v cc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40v magnetic amp. source voltage, v m . . . . . . . . . . . . . . . . . . . . . . . . 40v reset output voltage, v r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C120v total current source voltage, v m -v r . . . . . . . . . . . . . . . . . . C140v amplifier input range . . . . . . . . . . . . . . . . . . . . . . C0.3v to v cc reset input current, i dr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C10ma power dissipation at t a = 25c q, n, dp package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2w j, l package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1w power dissipation at t (leads/case) = 25c q, n, dp package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5w j, l package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2w operating temperature range . . . . . . . . . . . . C55c to +125c storage temperature range . . . . . . . . . . . . . C65c to +150c lead temperature (soldering, 10 sec) . . . . . . . . . . . . . . 300c note: all voltages are with respect to ground pins. all currents are positive into the specified terminal. consult packaging section of databook for thermal limitations and considerations of package. dr 2 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 dr 1 reset gnd gnd v m v cc v ref c/l out c/l n.i. in c/l inv. in gnd gnd e/a inv. in e/a n.i. in e/a out connection diagrams dil-16, soic-16 (top view) j or n package, dp package 3 18 17 16 n/c 1 22019 15 14 4 5 6 7 8 911 10 12 13 c/l out c/l n.i. in dr2 dr1 reset n/c n/c gnd v m c/l inv. in gnd n/c n/c e/a inv. in v cc v ref n/c e/a n.i. in e/a out plcc-20, lcc-20 (top view) q, l packages note: all four ground pins must be connected to a common ground temperature range package uc1838aj C55 c to +125 c ceramic dip uc1838al clcc uc2838adp C20 c to +85 c power soic uc2838an plastic dip uc2838aq plcc uc3838adp 0 c to +70 c power soic uc3838an plastic dip UC3838AQ plcc ordering information
3 uc1838a uc2838a uc3838a electrical characteristics: unless otherwise stated, these specifications apply for t a = C55c to +125c for the uc1838a, C20c to +85c for the uc2838a, and 0c to +70c for the uc3838a, v cc = 20v, v m = 5v, t a =t j . parameter test conditions uc1838a / uc2838a uc3838a units min typ max min typ max reference section supply current v cc =v m = 40v 4 8 4 8 ma reference output t a = 25c 2.47 2.5 2.53 2.45 2.5 2.55 v line regulation v cc = 5 to 30v 1 5 1 10 mv load regulation i o = 0 to C2ma 5 20 5 20 mv short circuit current v ref = 0v C30 C60 C30 C60 ma temperature stability* over operating temp. range 15 25 10 25 mv amplifier section (each amplifier) offset voltage v cm = 2.5v 5 10 mv input bias current v in = 0v C1 C1 m a input offset current 100 100 na minimum output swing 0.4 18 0.4 18 v output sink current v o = 5v 1103011030ma output source current v o = 0v C1 C10 C20 C1 C10 C20 ma a vol v o = 1 to 11v 100 120 100 120 db c mrr v in = 1 to 11v 70 80 70 80 db p srr v cc = 10 to 20v 70 100 70 100 db gain bandwidth* 0.6 0.8 0.6 0.8 mhz reset drive section input leakage v dr = 40v 10 10 m a output leakage v r = C120v C100 C100 m a input current i r = C50ma C1 C2 C1 C2 ma maximum reset current i dr = C3ma C100 C120 C200 C100 C120 C200 ma transconductance i r = C10 to C50ma .03 .042 .055 .03 .042 .055 a/v * these parameters are guaranteed by design but not 100% tested in production. typical application +12v, 4a output with switching frequency = 50 khz.
4 uc1838a uc2838a uc3838a application information figure 1. amplifier open loop response. figure 2. reset driver-input current. figure 5. reset driver-input voltage. figure 3. reset driver-output impedance. figure 6. reference temperature coefficient. unitrode corporation 7 continental blvd. ? merrimack, nh 03054 tel. (603) 424-2410 ? fax (603) 424-3460 figure 4. reset driver response.
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