ADP5091ACPZ-1-R7 datasheet(20/28 Pages) AD

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ADP5091/ADP5092

Data Sheet

Rev. A | Page 20 of 28

POWER GOOD (PGOOD)

The ADP5091/ADP5092 allow users to set a programmable

PGOOD voltage threshold, which indicates that the SYS voltage

is at an acceptable level. It must be set by using external resistors.

Figure 42 shows the VSETPG falling threshold voltage given by

Equation 11.













HYST

PG2

PG1

REF

INT

FALLING

SETPG

(11)

The SETHYST pin can program the hysteresis with an external

resistor (RPG_HYST) given by Equation 12.













PG2

HYST

PG1

REF

INT

RISING

SETPG

(12)

Considering the quiescent current consumption, the sum of the

resistors that comprise the power-good resistor divider

(RPG_HYST, RPG1, and RPG2) must be more than 6 MΩ, that is,

RPG_HYST + RPG1 + RPG2 ≥ 6 MΩ

The logic high level on PGOOD is equal to the SYS voltage and

the logic low level is ground. The logic high level has approximately

11.6 kΩ (typical) internally in series to limit the available current.

The VSETPG_FALLING threshold must be greater than the VSETSD

threshold.

For the best operation of the system, use PGOOD to enable the

system load or to turn on an ultralow power load switch or to

drive an external positive channel field effect transistor (PFET)

between SYS and the system load via an inverter to determine

when the system load can be connected or removed (see Figure 48).

Table 8 shows programming threshold resistor examples

corresponding to various voltages with a 10 MΩ resistor divider.

Figure 43 shows various threshold voltages states.

COLD STARTUP

MAIN BOOST

CHARGER ON

ENABLE CHIP

CHARGING BATTERY

VSYS_TH

VSYS_CHG

VSYS_CHG_HYS

VSYS_TH

TURN ON MAIN BOOST IN

ASYNCHRONOUS MODE

VSETSD

VSETSD_HYS

MAIN BOOST IN

SYNCHRONOUS MODE

TURN ON SWITCH BETWEEN

BSTO AND BAT

VSETPG_FALLING

VSETPG_RISING

PGOOD BECOMES HIGH

VBAT_TERM_HYS

VBAT_TERM

MAIN BOOST

CHARGER OFF

MAXIMUM DEVICE

RATING VOLTAGE

TURN OFF MAIN BOOST

Figure 43. ADP5091/ADP5092 Various Threshold Voltages States (See

Equation 8 and Equation 9)

POWER PATH WORKING FLOW

Figure 44 shows the power switches structure when the backup

primary battery is used. During the cold start, when a primary

battery connects to the BACK_UP pin, the S1 switch turns on.

The primary battery with the Diode D1 forward voltage drop

can be the SYS power source.

After completing the cold start, if the BAT voltage is above the

SETBK falling threshold, the BACK_UP switches remain off.

When the BAT voltage is lower than the SETBK falling threshold,

the backup control automatically selects the high voltage terminal

as the SYS power source as long as the SYS voltage is more than

VSYS_CHG. The backup control also prevents the BACK_UP

primary battery from charging the BAT pin. Meanwhile, the BAT

offset of the comparator prevents the input source from

charging the BACK_UP primary battery. Table 9 shows the

power path of the working state.

BAT

–

BSTO

BACK_UP

BACK_UP_M1

BACK_UP_M2

SYS SWITCH

BAT_M1

BAT_M2

SYS

GATE DRIVER

GATE

DRIVER

Figure 44. ADP5091/ADP5092 Power Switches Structure

CURRENT-LIMIT AND SHORT-CIRCUIT PROTECTION

The boost regulator and regulated output in hysteresis boost mode

in the ADP5091/ADP5092 includes current-limit protection

circuitry to limit the amount of positive current flowing through

the low-side boost switch. The boost regulator current-limit

protection circuitry is a cycle-by-cycle, three-level peak current-

limit protection with a third level of 200 mA (typical), and the

regulated output current-limit protection circuitry is 100 mA

(typical). In LDO mode, the current-limit protection is designed

to limit the current when the output load reaches 260 mA

(typical). When the output load exceeds 260 mA, the output

voltage reduces to maintain a constant current limit.

Although there is no current limit at the SYS and the BAT pins,

it is recommended to limit the system load current to lower

than 1000 mA. The total resistance of the SYS switch and the

BAT switch (1.03 Ω, typical) generates a voltage drop when the

system load sinks a large current from BAT. It is also necessary

to consider the internal resistance of the storage elements

connected to the BAT pin.

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