ABSOLUTE MAXIMUM RATINGS
SPECIFICATIONS
MP38 • MP38A
BYPASSING
GENERAL
Properbypassingofthepowersupplypinsiscrucialforproper
operation. Bypass the ±Vs pins with a aluminum electrolytic
capacitor with a value of at least 10µF per amp of expected
output current. In addition a .47µF to 1µF ceramic capacitor
should be placed in parallel with each aluminum electrolytic
capacitor. Both of these capacitors have to be placed as close
tothepowersupplypinsasphysicallypossible.Ifnotconnected
to the Vs pins (See BOOST OPERATION) the VB pins should
also be bypassed with a .47µF to 1µF ceramic capacitor.
Please read Application Note 1 "General Operating Con-
siderations" which covers stability, supplies, heat sinking,
mounting, current limit, SOA interpretation, and specification
interpretation. Visit www.apexmicrotech.com for design tools
that help automate tasks such as calculations for stability,
internal power dissipation, current limit; heat sink selection;
Apex’s complete Application Notes library; Technical Seminar
Workbook; and Evaluation Kits.
CURRENT LIMIT
USING THE IQ PIN FUNCTION
Thetwocurrentlimitsenselinesaretobeconnecteddirectly
acrossthecurrentlimitsenseresistor. Forthecurrentlimitto
work correctly pin 24 must be connected to the amplifier
output side and pin 23 connected to the load side of the
current limit resistor, RCL, as shown in Figure 1. This con-
nection will bypass any parasitic resistances, Rp, formed by
sockets and solder joints as well as internal amplifier losses.
The current limiting resistor may not be placed anywhere in
the output circuit except where shown in Figure 1.
The value of the current limit resistor can be calculated as
follows:
Pin 25 (Iq) can be tied to pin 6 (Cc1) to eliminate the class
AB biasing current from the output stage. Typically this would
remove 1-4 mA of quiescent current. The resulting decrease
in quiescent power dissipation may be important in some
applications. Note that implementing this option will raise the
output impedance of the amplifier and increase crossover
distortion as well.
COMPENSATION
The external compensation components CC and RC are con-
nected to pins 4 and 6. Unity gain stability can be achieved at
any compensation capacitance greater than 470 pF with at
least 60 degrees of phase margin. At higher gains more phase
shift can be tolerated in most designs and the compensation
capacitance can accordingly be reduced, resulting in higher
bandwidth and slew rate.
.7
I LIMIT
RCL
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APPLICATION REFERENCES
For additional technical information please refer to the fol-
lowing application notes.
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AN 1
AN 11
AN 38
General Operating Considerations
Thermal Techniques
Loop Stability with Reactive Loads
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BOOST OPERATION
With the V feature the small signal stages of the amplifier
areoperatedBathighersupplyvoltagesthantheamplifier'shigh
current output stage. +VS (pins 12-14) and –V (pins 18-20)
are connected to the high current output stage.SAn additional
10V on the VB pins is sufficient to allow the small signal stages
to drive the output transistors into saturation and improve the
outputvoltageswingforextraefficientoperationwhenrequired.
When close swing to the supply rails is not required the +V
and +V pins must be strapped together as well as the –VBB
and –VSSpins. The boost voltage pins must not be at a voltage
lower than the VS pins.
This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.
4APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: 1 (800) 546-2739
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