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AD5100

Rev. 0 | Page 21 of 36

POWER REQUIREMENTS

INTERNAL POWER, VREG

The AD5100 internal power, VREG, is derived from V1MON and

becomes active when V2MON reaches 2.2 V. V2MON is used to turn

AD5100 on and off with a different behavior depending on the

V2MON monitoring mode selection.

By default, the AD5100 turns on when the voltage at V2MON rises

above the logic threshold, V2MON_ON. When V2MON falls below the

logic threshold, V2MON_OFF, AD5100 turns off 2 seconds after

SHDN is deasserted. Note that AD5100 requires 5 μs to start up

and that V1MON must be applied before V2MON. Extension of the

AD5100 turn-off allows the system to complete any housekeeping

tasks before the system is powered off.

shows the

default V2MON and VREG waveforms.

Figure 19

Rising Edge Triggered Wake-Up Mode

If rising edge triggered wake-up V2MON mode is selected instead,

the AD5100 does not turn off when V2MON returns to a logic low.

To configure the part into rising edge triggered mode, set the

V2MON off threshold register, Register 0x04[3:1], to 1001.

In this mode, once the part is powered on, it can only be powered

down by an I2C power-down instruction or by removing the

supply on the V1MON pin. To power down the part over the I2C

bus while in rising edge triggered mode, the user must first

ensure that the software power down feature is enabled.

•

The user must then write to Register 0x17[0], to actually power

down the AD5100.

•

This feature is for applications that use a wake-up signal.

VOTP

A 5.5 V supply voltage is needed only during OTP fuse program-

ming. This voltage should be provided by an external source

during factory programming and should have 5.5 V/100 mA

driving capability. The OTP programming takes a maximum of

12 ms for each register. VOTP is not required for normal operation.

The VOTP has dual functions; it is used for programming the non-

volatile memory fuse arrays, as well as serving as a compensation

network for internal power stability. As a result, a bypass capacitor

must be connected at the VOTP pin at all times. A low ESR 10 μF

tantalum capacitor is recommended.

AD5100 achieves the OTP function through blowing internal

fuses. Users should always apply the 5.5 V one-time programmable

voltage at the first fuse programming attempt. Failure to comply

with this requirement may lead to a change in the fuse struc-

tures, rendering programming inoperable.

Poor PCB layout introduces parasitic inductance that may affect

the fuse programming voltage. Therefore, it is mandatory that a

10 μF tantalum capacitor be placed as close as possible to the

VOTP pin. The value and the type of C2 are important. It should

provide both a fast response and large supply current handling

with minimum supply droop during programming (see Figure 18).

6V TO 30V

3V TO 30V

APPLY ONLY 5.5V FOR OTP

V1MON

V2MON

VOTP

AD5100

10µF

Figure 18. Power Supply Requirement

V2MON

V2MON_ON*

V2MON,IH

t2SD_HOLD*

tVREG_OFF_DELAY

tGLITCH

t2SD_DELAY*

V2MON_ON*

V2MON_OFF*

tVREG_ON_DELAY

SHDN

VREG

NOTES

1. 6V < V1MON < 30V

2. * = PROGRAMMABLE

t2SD_DELAY*

Figure 19. Internal Power VREG vs. V2MON Timing Diagrams (Default)

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