ADM1085 Voltage Sequencer with Active High, Open-Drain Enable Output

The ADM1085-ADM1088 are Simple Sequencing™ circuits which provide a time delay between the enabling of voltage regulators at power-up in multiple supply systems. When the output voltage of the first regulator reaches a preset threshold, a time delay is initiated before an enable signal allows subsequent regulators to power-up. Any number of these devices can be cascaded with regulators to allow sequencing of multiple power supplies.

Threshold levels can be set with a pair of external resistors in a voltage divider configuration. By choosing appropriate resistor values, the threshold can be adjusted to monitor voltages as low as 0.6V.

The ADM1086 and ADM1088 have push-pull output stages, with active-high (ENOUT) and active-low (ENOUT) logic outputs, respectively. Similarly, the ADM1085 has an active-high (ENOUT) logic output and the ADM1087 has an active-low (ENOUT) output. Both the ADM1085 and ADM1087 have open-drain output stages which can be pulled up to voltage levels as high as 22V through an external resistor. This level shifting property of the ADM0185 and ADM1087 ensures compatibility with enable input logic levels of different regulators and converters.

All four models have a dedicated enable input pin which allows the output signal to the regulator to be controlled externally. This is an active-high input (ENIN) for the ADM1085 and ADM1086, and an active-low input (ENIN) for the ADM1087 and ADM1088.

The Simple Sequencers™ are specified over the extended –40°C to +125°C temperature range, and with low current consumption of 15µA (typ) and 6-lead SC70 packaging, they are suitable for low power portable applications.

Features and Benefits

Provide time delays between enabling of regulators
Can be cascaded with regulators for multiple supply sequencing
Output stages
High voltage (up to 22 V) open-drain output (ADM1085/ADM1087)
Push-pull output (ADM1086/ADM1088)

Power supply monitoring from 0.6 V
Capacitor adjustable time delays
High voltage (up to 22 V) enable input
Low power consumption (15 µA)
Specified over –40°C to +125°C temperature range
6-lead SC70 package

Power Management

Data Sheets

Document	note
ADM1085/ADM1086/ADM1087: Simple Sequencers® in 6-Lead SC70 Data Sheet (Rev. B)	PDF 285 kB

Application Notes

Document	note
AN-1080: Power-Up and Power-Down Sequencing Using the ADM108x Simple Sequencer (Rev. 0)	PDF 384 kB
AN-726: Triple-Supply Power-Good Indication with the ADM108x (Rev. 0)	PDF 75 kB