Maxim Integrated Products introduces the MAX6877-MAX6883 dual/triple power-supply trackers/sequencers. These devices control up to three power-supply rails to ensure proper power-up and power-down conditions for systems requiring voltage tracking or sequencing. Key performance parameters, such as voltage thresholds, slew rates, and timing parameters, are adjusted with external resistors or capacitors.
To turn on the MOSFETs, the MAX6877-MAX6883 employ independent charge pumps that ensure a 5.5V gate-to-source enhancement. During initial power up, all monitored voltages must exceed their resistor-set threshold levels before the voltages are switched on through the external n-channel MOSFET. In sequence mode, all MOSFETs are turned on sequentially with a capacitor-set time delay between each rail as they power up. In track mode, the voltage at the source of each MOSFET is monitored and then compared to each other. The gate of each MOSFET is continuously adjusted in this close-loop control system to ensure that the voltage track is within 125mV of the reference ramp.
In the sequencing or tracking mode, if any of the voltages fails to sequence or track within specifications, a fault condition is asserted and all the MOSFETs are turned off quickly. Internal 100 ohm pulldown circuitry is activated to help discharge the capacitance at the output.
The MAX6877/MAX6878/MAX6879 track or sequence voltages, while the MAX6880-MAX6883 only sequence voltages. The MAX6877/MAX6880/MAX6881 control three power-supply rails, while the MAX6878/MAX6879/MAX6882/MAX6883 control two power-supply rails.
All devices feature a capacitor-adjustable slew-rate input that controls the ramp rate of each voltage at the output. Other features include a margin disable input, an enable input, and a power-good output. The MAX6877/MAX6878/MAX6879 also feature latchoff and an autoretry mode if the supplies fail to power up.
The MAX6877-MAX6883 are available in 4mm x 4mm, 24- or 16-pin TQFN packages and are fully specified from -40 degrees Celsius to +85 degrees Celsius. Prices start at $2.47 (1000-up, FOB USA). Evaluation kits are available to simplify design.
A preliminary Data Sheet for this product is available at:
MAX6877 data sheet
MAX6880 data sheet