xe8802 Semtech Corporation, xe8802 Datasheet - Page 144

• Manufacturer Part Number: xe8802
• Description: Data Acquisition Soc With 16+10 Bit Zoomingadc? Embedded Risc Controller And Lcd Driver
• Manufacturer: Semtech Corporation

18.1 Features
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18.2 Overview
The Vmult block generates a voltage (called “Vmult”) that is higher or equal to the supply voltage. This output
voltage is intended for use in analog switch drivers, for example in the ADC and PGA block.
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The voltage multiplier should be on (bit Enable in RegVmultCfg0) when using switched analog blocks, like ADC,
DAC or analog properties of Port B when Vbat is below 3V. The source clock of Vmult is selected from Fin[1:0] in
RegVmultCfg0. It is strongly recommended to use the same Fin bit code as in the ADC.
The external capacitor on the pin VMULT has to be connected if the block is enabled. The size of the capacitor
has to be 2nF ± 50%.
18.3 Control part Registers
There is only one register in the Vmult. Table 18-1 describes the bits in the register.
Pos.
2
1-0
© Semtech 2006
Generates a voltage that is higher or equal to the supply voltage, but at maximum 4.8 V
Can be easily enabled or disabled
In normal use its value is 4.8 V, this voltage is available on the pad Vmult.
When the main voltage is below 2.6 V, Vmult is twice the main voltage minus 0.4 V.
When the main voltage is above 4.8 V, Vmult remains 4.8 V but the internal voltage intended for the analog
switch drivers equal the main voltage.
Table 18-1. RegVmultCfg0
RegVmultCfg0
Enable
Fin
rw
rw
rw
Figure 17-1 : Structure of the Vmult peripheral
Vmult_dl
Reset
0
0
prescaler
XE8802 Sensing Machine Data Acquisition MCU
regs
Function
enable of the vmult
‘1’ : enabled
‘0’ : disabled
system clock division factor
‘00’ : 1/2,
‘01’ : 1/4,
‘10’ : 1/16,
‘11’ : 1/64
en_vmult
ck_vmult
VMULT
18-2
(analog)
with ZoomingADC™ and LCD driver
switch power
Vmult
(capacitor only required
when enabled)
(other blocks)
switched
analog
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