LTM8024 datasheet(10/26 Pages) AD

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LTM4709

Rev. 0

For more information www.analog.com

OPERATION

The LTM4709 is a high-density, low voltage, triple 3A

μModule linear regulator that offers high PSRR, ultralow

noise, and ultrafast transient response. The device sup-

plies up to 9A output current with a typical dropout voltage

of 45mV. Output voltage noise of 1.3µVRMS (BW = 10Hz

to 100kHz) is achieved with no reference bypass capaci-

tor required. The power supply rejection ratio (PSRR) at

1MHz is 51dB at full load with 300mV difference between

input and output. The LTM4709’s high bandwidth

provides an ultrafast transient response that only requires

just a single ceramic output capacitor (10µF minimum),

saving bulk capacitance, PCB area, and cost. LTM4709

has the industry’s best performance of high-frequency

PSRR and low-frequency RMS noise at its current range

and provides 9A output current in a compact size with

outstanding thermal performance.

New generation of FPGA and ASIC processors place

stringent demands on the power supplies for the core,

ADCs, DACs, low noise amplifier, and transceiver chan-

nels. These applications require a power supply with a

fast transient response and low noise. The processor load

may change from near zero to a few amps in hundreds

of nanoseconds. Output voltage specifications, especially

in the 1V range, require tight tolerances on the transient

response. The supply voltages need to have low noise

and high bandwidth to achieve the low bit-error rates.

These requirements mandate the need for high current,

accurate, ultralow noise, ultrafast regulator operating at

low input and output voltages.

The LTM4709 is ideal for high-performance FPGAs,

microprocessors, noise-sensitive power supplies, and

high-current applications that operate over low input and

output voltages. Output voltage for the LTM4709 is dig-

itally selectable in 50mV increments from 0.5V to 1.2V;

100mV increments from 1.2V to 1.8V; and discrete levels

at 2V, 2.5V, 3V, 3.3V, and 4.2V. The LTM4709 provides a

precision output current monitor with ±2.4% accuracy at

3A per channel. Terminating the current monitor (IMON)

pin to GND with a resistor produces a voltage proportional

to the output current, which allows for the measurement

of the output current.

The LTM4709 incorporates a unique tracking function

which controls the output voltage of an upstream switch-

ing regulator powering the LTM4709’s input (see Figure 2

and Figure 3). This tracking function drives the upstream

switching regulator to maintain a constant voltage across

LTM4709. This input-to-output voltage control allows the

user to change the output voltage of LTM4709, maximize

the efficiency, and maintain the high PSRR performance.

The LTM4709’s architecture drives an internal N-channel

power MOSFET as a source follower. This configuration

permits a user to have an extremely low dropout, ultra-

fast transient response with excellent PSRR performance,

as well as providing significant cost savings on the PCB

and external components. LTM4709 internal protection

includes undervoltage lockout (UVLO), precision current

limiting with power foldback and thermal shutdown. The

LTM4709 is offered in a compact size of 6mm × 12mm

× 1.92mm. It offers excellent thermal performance

with less than 70°C junction temperature at 9A output

current and ambient temperature of 25°C (see Figure 5).

For applications where high ambient temperature (>70°C)

is required, the 150°C rated version of LTM4709 is

available.

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