SC4607
POWER MANAGEMENT
Pin Configuration
Top View
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.
(10 Pin MSOP)
Pin Descriptions
Pin #
1
Pin Name
BST
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.
4
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2
3
VC C
ISET
4
COMP
5
FS/SYNC
6
VSENSE
7
GND
2005 Semtech Corp.
SEMTECH [ SEMTECH CORPORATION ]
