The MAX8513/MAX8514 integrate a voltage-mode
PWM step-down DC-DC controller and two LDO controllers,
a voltage monitor, and a power-on reset for the
lowest-cost power-supply and monitoring solution for
xDSL modems, routers, gateways, and set-top boxes.
The DC-DC controller switching frequency can be set
with an external resistor from 300kHz to 1.4MHz, to allow
for the optimization of cost, size, and efficiency. For noisesensitive
applications, the DC-DC controller can also be
synchronized to an external clock, minimizing noise interference.
Operation above 1.1MHz reduces noise for high
data-rate xDSL applications. An adjustable soft-start and
adjustable foldback current limit provide reliable startup
and fault protection. The DC-DC controller output voltage
can be set externally to a voltage from 1.25V to 5.5V.
Current limiting is accomplished by inductor current sensing
for improved efficiency, or by an external sense resistor
for better accuracy.
The MAX8513/MAX8514s' first LDO controller is
designed to provide a low-cost, high-current regulated
output from 0.8V to 5.5V using an N-channel MOSFET or
a low-current output using a low-cost NPN transistor. The
MAX8513's second regulator can be used to generate
0.8V to 27V output with a low-cost PNP transistor. Both LDO regulators can operate either from the DC-DC controller output or from a higher voltage derived with a flyback overwinding on the DC-DC converter inductor. The MAX8514's second LDO regulator is designed to provide a negative output with an NPN transistor.
A sequence input allows the outputs to either power up together, or for the DC-DC regulator to power up first and each LDO controller to power up in sequence. An input power-fail output (active-low PFO) is provided for input power-fail warning, such as in dying-gasp applications. A power-on reset circuit with a 140ms delay is also included to indicate when all outputs have achieved regulation and stabilized.
Applications
- Set-Top Boxes
- Wireless Routers
- xDSL, Cable, ISDN Modems, and Routers
