Data Sheet

ADP5090

Rev. C | Page 13 of 21

BACKUP STORAGE PATH

The ADP5090 provides an optional backup storage energy path,

an integrated backup controller, and two back to back power

switches between the BACK_UP pin and the SYS pin. When the

system operates at a condition where the harvested and stored

energy is periodically insufficient, a backup energy storage

element can be attached to the BACK_UP pin. The backup

controller enables when the SYS voltage is above 1.5 V (typical).

When the BACK_UP pin voltage is higher than the BAT pin

voltage, it turns on the internal power switches between the

BACK_UP pin and the SYS pin. When the BACK_UP pin

voltage is lower than the BAT pin voltage, the internal power

switches are turned off. The 185 mV (typical) comparator input

offset of the BAT pin prevents the input source and BAT pin

charging the BACK_UP pin (see Figure 32).

In addition, the backup storage element can bypass the cold

startup with inrush current protection circuitry. When the

system current exceeds the internal current limit of 400 mA

(typical), the BACK_UP switches turn off. Nevertheless, the

current capability is only 250 µA (typical) when plugging in the

backup battery for the first time. Restricting the system load

current from the SYS pin ensures that the power path can enter

normal operation status. Table 6 explains the power path working

state. For long-term store mode, remove the backup storage

element and then discharge SYS to ground.

MINOP FUNCTION

When the energy generated by the harvester cannot sustain the

steady working state, the MINOP function can disable the boost

regulator to prevent discharging the storage element. The

MINOP function disables the MPPT function to achieve the

lowest quiescent current of 260 nA (typical). When the voltage

of the CBP pin decreases to the threshold set by the resistor at

the MINOP pin, the boost regulator stops switching. Disable

this function by connecting MINOP to AGND. The typical

MINOP bias current is 2 μA.

DISABLING BOOST

For noise or EMI sensitive applications, the boost switcher can

be stopped temporarily by pulling the DIS_SW pin high to

prevent interference with RF circuits. The boost switching

resumes when the DIS_SW pin is pulled low. The transition

delay is less than 1 μs (typical).

BATTERY OVERCHARGING PROTECTION

To prevent rechargeable batteries from being overcharged and

threshold voltage given by Equation 2.

















+

=

TERM2

TERM1

REF

TERM

BAT

R

R

V

V

1

2

3

_

(2)

Considering the quiescent current consumption, the sum of the

resistors must be more than 6 MΩ, that is,

which is internally set to the overvoltage threshold minus an

boost regulator is disabled. The main boost starts again when

input energy is excessive, the VBAT pin voltage ripples between

Figure 30. The ADP5090 Program Paramater Setting

BATTERY DISCHARGING PROTECTION

To prevent rechargeable batteries from being deeply discharged

must be set by using external resistors. Figure 30 shows the













+

=

SD2

SD1

REF

SD

BAT

R

R

V

V

1

_

(3)

(typical), to program the hysteresis, given by Equation 4.

E

HYS

SD

BAT

SD

BAT

HYS

SD

BAT

R

R

V

V

_

_

_

_

_

×

=

(4)

hysteresis.

Considering the quiescent current consumption, the sum of the

BAT

TERM_REF

SYS

REF

SETSD

STEPG

TERM

SDB

PG

SDB

TERMS

SDS

PGS

PG

TRM

TERM_REF

BAT

R

2R

TERM

CONTROL