MIC2593
Micrel
Gate Capacitor and Resistor Guidelines
frequency MOSFET source-follower oscillations from occur-
ring. The exact value of the resistors used is not critical; 10Ω
The MIC2593 controls four external power MOSFETs, that
handle the high currents for each of the two 3.3V and 5V
outputs. A capacitor is connected in the application circuit
from each GATE pin of the MIC2593 to ground. However, an
to 33Ω is usually a sufficient choice. Each R
should be
GATE
physically located directly adjacent to the MOSFET gate lead
to which it connects.
external capacitor, C
MIC2593. Each C
, is not required for operation of the
controls the ramp-up rate of its
GATE
MIC2593
GATE
respective power output (e.g., 5VOUTB). These capacitors,
which are typically in the 10nF range, cause the GATE
outputs of the MIC2593 to have very low AC impedances to
ground at any significant frequency. It is therefore necessary
RGATE
15Ω
External
MOSFET
GATE
CGATE
10nF
to place a modest value of gate damping resistance (R
)
GATE
betweeneachC
as shown in Figure 15. These resistances prevent high-
andthegateofitsassociatedMOSFET
GATE
Figure 15. C
and R
Connection
GATE
GATE
April 2004
25
M9999-042204
STMICROELECTRONICS [ ST ]
