MC34717(2007) 查看數據表（PDF） - Freescale Semiconductor

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MC34717
(Rev.:2007)

5.0 A 1.0 MHz Fully Integrated Dual Switch-Mode Power Supply

Freescale Semiconductor 

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

Today’s advanced systems are increasingly requiring

more efficient and accurate power supplies. They present a

set of challenges that include highly accurate voltage

regulation, high current and fast transient response

capability, voltage monitoring (power sequencing), and

increased operating frequency. Point of Load power supplies

offer adequate solutions to these challenges. They are non-

isolated DC to DC converters that are located near their load

and take their input voltage from an intermediate not,

necessarily, regulated bus. their close proximity to the load is

of a high importance with newer device requirements. While

meeting the challenges, they allow for higher efficiency,

localized protection, and minimum distribution losses. Their

compact design and value makes them cost effective.

The 34717 is a PoL dual output power supply. Its

integrated solution offers a cost effective system and reliable

operation. It utilizes a voltage mode synchronous buck

switching converter topology with integrated low RDS(ON)

(50 mΩ) N-channel power MOSFETs for higher efficiency

operation. It provides an output voltage with an accuracy of

less than ±2.0 %, and capable of supplying up to 5.0 A of

continuous current from both channels. The second output

tracking abilities makes it ideal for systems with multiple

related supply rails. It has a programmable switching

frequency that allows for flexibility and optimization over the

operating conditions and can operate at up to 1.0 MHz to

significantly reduce the external components size and cost. It

also provides the ability to program the over current limit for

both channels. It protects against output over current,

overvoltage, undervoltage, and overtemperature conditions.

It also protects the system from short circuit events. It

incorporates a power good output signal to alert the host

when a fault occurs.

It can be enabled and disabled by controlling the SD pin,

which offers power sequencing capabilities.

By integrating the control/supervisory circuitry along with

the Power MOSFET switches for the buck converter into a

space-efficient package, the 34717 offers a complete, small-

size, cost-effective, and simple solution to satisfy the needs

of today’s systems.

FUNCTIONAL PIN DESCRIPTION

BOOTSTRAP INPUT (BOOT1, BOOT2)

Bootstrap capacitor input pin. Connect a capacitor (as

discussed in Bootstrap capacitor on page 19) between this

pin and the SW pin of the respective channel to enhance the

gate of the high-side Power MOSFET during switching.

OUTPUT VOLTAGE DISCHARGE PATH (VOUT1,

VOUT2)

Buck converter output voltage is connected to this pin. It

only serves as the output discharge path once the SD signal

is asserted.

POWER INPUT VOLTAGE (PVIN1, PVIN2)

Buck converter power input voltage. This is the drain of the

buck converter high-side power MOSFET.

SWITCHING NODE (SW1, SW2)

Buck converter switching node. This pin is connected to

the output inductor.

POWER GROUND (PGND1, PGND2)

Buck converter and discharge MOSFETs power ground. It

is the source of the buck converter low-side power MOSFET.

COMPENSATION INPUT (COMP1, COMP2)

Buck converter external compensation network connects

to this pin. Use a type III compensation network.

ERROR AMPLIFIER INVERTING INPUT (INV1, INV2)

Buck converter error amplifier inverting input. Connect the

output to the INV pin through a resistor divider.

INTERNAL SUPPLY VOLTAGE OUTPUT (VDDI)

This is the output of the internal bias voltage regulator.

Connect a 1.0 µF, 6 V low ESR ceramic filter capacitor

between this pin and the GND pin. Filtering any spikes on this

output is essential to the internal circuitry stable operation.

SIGNAL GROUND (GND)

Analog ground of the IC. Internal analog signals are

referenced to this pin voltage.

INPUT SUPPLY VOLTAGE (VIN)

IC power supply input voltage. Input filtering is required for

the device to operate properly.

POWER GOOD OUTPUT SIGNAL (PG)

This is an active low open drain output that is used to

report the status of the device to a host. This output activates

after a successful power up sequence and stays active as

long as the device is in normal operation and is not

experiencing any faults. This output activates after a 10 ms

Analog Integrated Circuit Device Data

Freescale Semiconductor

34717

11

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