SC4607 データシートの表示（PDF） - Semtech Corporation

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SC4607

Very Low Input, MHz Operation,High Efficiency Synchronous Buck

Semtech Corporation 

SC4607

POWER MANAGEMENT

Pin Configuration

Top View

(10 Pin MSOP)

Ordering Information

Part Number

SC4607IMSTR

SC4607IMSTRT(2)

Device

MSOP-10

Notes:

(1) Only available in tape and reel packaging. A reel

contains 2500 devices.

(2) Lead free product. This product is fully WEEE and

RoHS compliant.

Pin Descriptions

Pin #

Pin Name

1

BST

2

VCC

3

ISET

4

COMP

5

FS/SYNC

6

VSENSE

7

GND

Pin Function

This pin enables the converter to drive an N-Channel high side MOSFET. BST connects to

the external charge pump circuit. The charge pump circuit boosts the BST pin voltage to a

sufficient gate-to-source voltage level for driving the gate of the high side MOSFET.

Positive supply rail for the IC. For improved noise immunity, bypass this pin to GND with a

0.1 to 4.7µF low ESL/ESR ceramic capacitor.

The ISET pin is used to limit current in the high side MOSFET. The SC4607 uses the

voltage across the Vin and ISET pins in order to set the current limit. The current limit

threshold is set by the value of an external resistor (R3 in the Typical Application Circuit

Diagram). Current limiting is performed by comparing the voltage drop across the sense

resistor with the voltage drop across the drain to source resistance of the high side

MOSFET during the MOSFET's conduction period. The voltage drop across the drain to

source resistance of the high side MOSFET is obtained from the Vin and PHASE pins.

This is the output of the voltage amplifier. The voltage at this output is inverted internally and

connected to the non-inverting input of the PWM comparator. A lead-lag network from the

COMP pin to the VSENSE pin compensates for the two pole LC filter characteristics

inherent to voltage mode control. The lead-lag network is required in order to optimize the

dynamic performance of the voltage mode control loop.

The FS/SYNC pin sets the PWM oscillator frequency through an external timing capacitor

that is connected from the FS/SYNC pin to the GND pin. Sleep mode operation is invoked

by clamping the FS/SYNC pin to a voltage below 75mV. The typical supply current during

sleep mode is 10µA. The SC4607 can be operated in synchronous mode by inserting a

resistor in series between the timing capacitor and GND pin. The other terminal of the

timing capacitor will remain connected to the FS/SYNC pin.

This pin is the inverting input of the voltage amplifier and serves as the output voltage

feedback point for the Buck converter. VSENSE is compared to an internal reference value

of 0.5V. VSENSE is hardwired to the output voltage when an output of 0.5V is desired.

For higher output voltages, a resistor divider network is necessary (R7 and R9 in the Typical

Application Circuit Diagram).

Signal and power ground for the IC. All voltages are measured with respect to this pin. All

bypass and timing capacitors connected to GND should have leads as short and direct as

possible.

 2005 Semtech Corp.

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