Atmel ATA6264 - Manual (Page 20)

20
4929B–AUTO–01/07
ATA6264 [Preliminary]
7. Charge Pump
To supply the VSAT and VCORE drivers, an external charge pump is provided. Both FETs (1) are
driven by the high charge pump voltage V
CP
to ensure that they can be switched to a low-ohmic
state. For correct function of the charge pump, an external capacitor of C = 47 nF has to be con-
nected to pin SVSAT, and another of C = 100 nF to pin CP. A double diode has to be
implemented for proper function of the charge pump. An external series resistor is recom-
mended to suppress spikes during switching of the SVSAT. The CP block is supplied by EVZ
and VSAT voltage and starts to operate as soon as the thresholds for VK15, K30 and EVZ are
achieved. An additional start-up circuitry is implemented to support the VSAT driver during the
start-up phase, thus enabling a reliable system startup.
The charge pump has an output CP-OUT to supply the external circuitry, and can be switched
via the SPI. It is capable of 250 µA.
Figure 7-1. Block Diagram Charge Pump
Note: 1. Connected to the drivers (see Figure 5-3 )
SVSAT VSAT
REF REF
CP
I = 1.4 mA
Status
register
External circuit
Status
register
Serial
interface
EVZ
CP-Out