Data Sheet

ADL8140

RECOMMENDED POWER MANAGEMENT CIRCUIT

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Rev. 0 | 17 of 18

Figure 53 shows a recommended power management circuit that

uses the LT3083 low dropout (LDO) regulator. The LT3083 output

load current is supplied to the IN pin of the LT3083. Power for

the on-board control circuitry is applied to the VCONTROL pin of the

LT3083. A voltage that is at least 1.4 V higher than the output volt-

age must be applied to the VCONTROL pin. In Figure 53, VCONTROL

has been set to 5 V but could be set as low as 2.9 V for a 1.5 V

output voltage. The current into the CONTROL pin is typically 1.7 %

of the total output current.

The LT3083 can provide up to 3 A of load current. Assuming

that the ADL8140 is being used in a phased array application, a

single LT3083 can easily provide bus power for all of the ADL8140

devices in a 64-element array. A dropout voltage of 500 mV is

assumed based on a load current of 3 A. If the required load current

is lower, the voltage on the IN pin of LT3083 can be reduced to

improve efficiency. For example, for a load current of 1 A, the

dropout voltage drops to a worst case value of 160 mV.

For applications that require a lower dropout voltage, LT3033 can

be used. For a 3 A load, the worst case dropout voltage for the

LT3033 is 240 mV

Table 11 provides recommended resistor values to set the other

output voltages. In each case, the minimum input voltage (VIN)

voltage is specified based on a 3 A load and a 500 mV dropout

voltage.

Table 11. Recommended Resistor Values for the Various LDO Output Voltages

LDO VOUT (V)

R2 (kΩ)

Minimum VDD (V)

1.2

24.3

1.7

1.5

30.1

2.0

2.0

40.2

2.5

2.5

49.9

3.0

3.0

60.4

3.5

3.3

66.5

3.8

3.5

69.8

4.0

Figure 53. Recommended Power Management Circuit