12
ISOMET
5V
W0
1
3
2
W3
1
3
2
47k
W1
1
3
2
W2
1
3
2
RDAC3 = 255
W3 = 10Kohm
RDAC0 = 255
W0 = 0 ohm
RDAC2 = 0 - 255
V50_Control = 50,67MHz Pow er
RDAC1 = 0 - 255
V40_Control = 40.0MHz Pow er
VH
VL
The four digital pots are configured into a potential divider.
The main power control pots W1 and W2 are in parallel and equate to 5Kohm resistance.
The upper and lower limit adjustment Pots W3 and W0 apply to both 40MHz and 50MHz powers.
AD5254 configuration
RDAC2 defines the 50 MHz power control factor
V50_Control VL + (VH-VL) x W2/255
where W2= 8-bit value programmed into RDAC2
RDAC1 defines the 40 MHz power control factor
V40_Control = VL + (VH-VL) x W1/255
where W1= 8-bit value programmed into RDAC1
RDAC0 defines the lower limit pot
Lower pot resistance R_W0 = (255-W0)/255 x 10Kohm
Lower limit voltage VL = (R_W0) / (47K+R_W3+5K+R_W0)
RDAC3 defines the upper limit pot
Upper pot resistance R_W3 = (W3)/255 x 10Kohm
Upper limit voltage VH = (R_W0+5K) / (47K+R_W3+5K+R_W0)
