The MAX1964/MAX1965 power-supply controllers are designed to address cost-sensitive applications demanding voltage sequencing/tracking, such as cable modem consumer premise equipment (CPE), xDSL CPE, and set-top boxes. Operating off a low-cost, unregulated DC supply (such as a wall adapter output), the MAX1964 generates three positive outputs and the MAX1965 generates four positive outputs and one negative output to provide an inexpensive system power supply.
The MAX1964 includes a current-mode synchronous step-down controller and two positive regulator gain blocks. The MAX1965 has one additional positive gain block and one negative regulator gain block. The main synchronous step-down controller generates a high-current output that is preset to 3.3V or adjustable from 1.236V to 0.75 x VIN with an external resistive-divider. The 200kHz operating frequency allows the use of low-cost aluminum-electrolytic capacitors and low-cost power magnetics. Additionally, the MAX1964/MAX1965 step-down controllers sense the voltage across the low-side MOSFET's on-resistance to efficiently provide the current-limit signal, eliminating the need for costly current-sense resistors.
The MAX1964/MAX1965 generate additional supply rails at low cost. The positive regulator gain blocks use an external PNP pass transistor to generate low voltage rails directly from the main step-down converter (such as 2.5V or 1.8V from the main 3.3V output) or higher voltages using coupled windings from the step-down converter (such as 5V, 12V, or 15V). The MAX1965's negative gain block uses an external NPN pass transistor in conjunction with a coupled winding to generate -5V, -12V, or -15V.
All output voltages are externally adjustable, providing maximum flexibility. During startup, the MAX1964 features voltage sequencing and the MAX1965 features voltage tracking. Both controllers provide a power-good output that monitors all of the output voltages.
Key Features
Applications/Uses
4.5V to 28V Input Voltage Range
Master DC-DC Step-Down Converter:
Preset 3.3V or Adjustable (1.236V to 0.75 x VIN) Output Voltage
Fixed Frequency (200kHz) PWM Controller
No Current-Sense Resistor
Adjustable Current Limit
95% Efficient
Soft-Start
Two (MAX1964)/Four (MAX1965) Analog Gain Blocks:
Positive Analog Blocks Drive Low-Cost PNP Pass Transistors to Build Positive Linear Regulators
Negative Analog Block (MAX1965) Drives a Low-Cost NPN Pass Transistor to Build a Negative Linear Regulator
Power-Good Indicator
Voltage Sequencing (MAX1964) or Tracking (MAX1965)
Notes: **This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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