RC5051M-T ,Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
RC5051M-T ,Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
RC5051M-T ,Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
RC5051M-T ,Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
RC5051M-T ,Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
RC5051M-T ,Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
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RC5051MT-RC5051M-T
Programmable Synchro0us DC-DC Controller for Low Voltage Microprocessors
SummaryThe RC5051 can be substituted for the RC5050 in all appli-
cations, provided that pin 9 has no trace attached to it; and
pin 11 either has no trace attached, or is attached to power
(not signal) ground.
Differences between the RC5050
and the RC5051The RC5050 and the RC5051 are both programmable DC-
DC controllers for low voltage microprocessors. Their only
functional difference in an application is that the RC5051 is
designed to run a synchronous rectifier in place of the
RC5050’s freewheeling diode (see Figure 1).
In the RC5050, pin 9 is not connected, whereas in the
RC5051 it drives the gate of the synchronous MOSFET rec-
tifier. In the RC5050, pin 11 is not connected, whereas in the
RC5051 it is a power ground. Finally, in the RC5050, pin 7
powers the internal digital logic from +5V, whereas in the
RC5051 it powers the synchronous MOSFET’s gate driver.
Substituting the RC5051 into an
RC5050 CircuitAs long as the board layout for the RC5050 circuit left the
pins 9 and 11 unconnected, the RC5051 can be susbstituted
in, as far as these pins are concerned, without any problem:
since they are unconnected, the gate drive signal on pin 9
goes nowhere, and thus has no effect. The same holds for pin
11: the RC5051 has other power ground pins, and so its
absence has no effect.
The other situation in which the RC5051 can be substituted
for the RC5050 is one in which, again, the RC5050’s pin 9 is
unconnected; and pin 11 is attached to power ground, but
NOT signal ground. Since pin 11 in the RC5051 goes to
power ground, this clearly presents no problem. However,
if pin 11 is attached to signal ground in the circuit, power
ground currents will be mixed with signal ground, poten-
tially causing circuit upset.
If neither pin 9 nor pin 11 has a trace going to it, the
RC5051 may be substituted for the RC5050. If pin 9 has
no trace going to it, and pin 11 is attached to power
ground (NOT signal ground), the RC5051 may be
substituted for the RC5050. Other than in these two
cases, the the RC5051 should NOT be substituted for the
RC5050.The other remaining difference between the two ICs is the
function of pin 7. Although for both circuits it is connected
to +5V , in the RC5051 pin 7 runs the gate driver, and so the
extra DC current drain might possibly be a concern; one
might also be concerned about current spikes on this pin due
to shootthrough.
As it turns out, since the gate driver is unused, the additional
DC current drawn from pin 7 is minimal: typically less than
2mA, which will have no effect on the performance of the
circuit. As for current spikes, they are typically less than
10mA for 20nsec and so also will have no effect on opera-
tion, due to the bypass capacitors on the +5V line. The
connection on pin 7 thus requires no modification in a
substitution of the RC5051 for the RC5050.
