AD5171

TERMINAL VOLTAGE OPERATING RANGE

voltage boundary conditions, see Figure 29. Supply signals

clamped by the internal forward-biased diodes and should be

avoided.

GND

A

W

B

POWER-UP/POWER-DOWN SEQUENCES

Similarly, because of the ESD protection diodes, it is important

B, and W. Otherwise, the diode will be forward-biased such that

the users’ circuits. The ideal power-up sequence is in the

should be powered down last.

POWER SUPPLY CONSIDERATIONS

To minimize the package pin count, both the one-time

programming and normal operating voltages are applied to the

link technology that requires 6 V to blow the internal fuses to

achieve a given setting. On the other hand, it operates at 2.7 V to

5.5 V once the programming is complete. Such dual voltage

requires isolation between supplies. The fuse programming

supply (either an on-board regulator or rack-mount power

supply) must be rated at 6 V and be able to handle 400 ms and

100 mA of transient current for one-time programming. Once

programming is complete, the 6 V supply must be removed to

allow normal operation of 2.7 V to 5.5 V. Figure 30 shows the

simplest implementation using a jumper. This approach saves

one voltage supply, but draws additional current and requires

manual configuration.

AD5171

C2

0.1

µF

5V

CONNECT J1

HERE FOR OTP

C1

1

µF

J1

R1

50k

Ω

R2

250k

Ω

6V

CONNECT J1

HERE AFTER OTP

Figure 30. Power Supply Requirement

An alternate approach in 3.5 V to 5.5 V systems adds a signal

diode between the system supply and the OPT supply for

isolation, as shown in Figure 31.

AD5171

C2

0.1

µF

APPLY FOR OTP ONLY

C1

10

µF

D1

3.5V–5.5V

6V

Figure 31. Isolating the 6 V OPT Supply from the 3.5V to 5.5 V Normal

Operating Supply. The 6 V supply must be removed once OPT is complete.

AD5171

C2

0.1

µF

APPLY FOR OTP ONLY

C1

10

µF

10k

Ω

2.7V

6V

P1

P2

R1

P1 = P2 = FDV302P, NDS0610

Figure 32. Isolating the 6 V OPT Supply from the 2.7 V Normal Operating

Supply. The 6 V supply must be removed once OPT is complete.

For users who operate their systems at 2.7 V, it is recommended

to use the bi-directional low-threshold P-Ch MOSFETs for the

supplies isolation. As shown in Figure 32 assumes the 2.7 V

system voltage is applied first but not the 6 V. The gates of P1

are P2 are pulled to ground, which turns on P1 and subse-

few tenths of mV drop across P1 and P2. When the AD5171

also to the gates of P1 and P2 to turn them off. While the OTP

command is executing at this time to program AD5171, the

2.7 V source is therefore protected. Once the OTP is complete,

the tester withdraws the 6 V, and AD5171 setting is permanently

fixed.

Rev. PrC | Page 13 of 20

Preliminary Technical Data