HM3441 datasheet(4/8 Pages) HMSEMI

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VC1 (Pin 1):

Frequency compensation pin

GND (Pin 2):

Signal and Power Ground for the IC.

S1 (Pin 3):

Switch Pin Where the Internal Switches A and B are Connected. Connect inductor from

SW1 to SW2. An optional Schottky diode can be connected from SW1 to ground. Minimize trace length

to keep EMI down.

S2 (Pin 4):

Switch Pin Where the Internal Switches C and D are connected. For applications with output

voltages over 4.3V, a Schottky diode is required from SW2 to VOUT to ensure the SW pin does not

exhibit excess voltage.

GND (Pin 5):

Signal and Power Ground for the IC.

VOUT (Pin 6):

Output of the Synchronous Rectifier. A filter capacitor is placed

from VOUT to GND.

VIN (Pin 7):

Input Supply Pin, Internal VCC for the IC. A ceramic bypass capacitor as close to the VIN pin

and GND (Pin 5) is required.

EN (Pin 8):

Combined Soft-Start and Shutdown. Grounding this pin shuts down the IC. Tie to >1.5V to

enable the IC and > 1.8V to ensure the error amp is not clamped from soft-start. An RC from the

shutdown command signal to this pin will provide a soft-start function by limiting the rise time of the VC

pin.

VFB (Pin 9):

Feedback Pin. Connect resistor divider tap here. The output voltage can be adjusted from

1.8V to 4.6V. The feedback reference voltage is typically 0.1V.

VC (Pin 10):

Frequency compensation pin.

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The HM3441 employs a buck-boost DC/DC converter to generate the output voltage required to drive a

high current LED. This architecture permits high efficiency, low noise operation at input voltages above,

below or equal to the output voltage by properly phasing four internal power switches. The error amp

output voltage on the VC pin determines the duty cycle of the switches.

Since the VC pin is a filtered signal, it provides rejection of frequencies well below the factory trimmed

switching frequency of 1.1MHz. The low RDS (ON), low gate charge synchronous switches provide high

frequency pulse width modulation control at high efficiency.

Undervoltage Lockout

To prevent operation of the power switches at high RDS(ON), an undervoltage lockout is incorporated on

the HM3441. When the input supply voltage drops below approximately 1.9V, power switches and all

control circuitry are turned off except for the undervoltage block, which draws a few microamperes.

Shenzhen H&M Semiconductor Co.Ltd

http：//www.hmsemi.com

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