SC4905AIMSTRT Semtech, SC4905AIMSTRT Datasheet - Page 11

• Manufacturer Part Number: SC4905AIMSTRT
• Description: IC, VOLTAGE MODE PWM CTRL, 12V, MSOP-10
• Manufacturer: Semtech

Specifications of SC4905AIMSTRT

• Input Voltage: 48V
• Output Voltage: 500mV
• Output Current: 1mA
• Frequency: 1MHz
• Power Dissipation Pd: 180mW
• Supply Voltage Range: 0V To 12V
• Digital Ic Case Style: MSOP
• No. Of Pins: 10
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SC4905A/B
POWER MANAGEMENT
Application Information (Cont.)
START UP SEQUENCE
Initially during the power up, the SC4905 is in the under
voltage lock out condition. As the VDD supply exceeds
the UVLO limit of the SC4905 and the VFF pin exceeds
the line under voltage lock out of about 1.2V, the inter-
nal reference, oscillator, and logic circuitry are powered
up.
The OUT driver is not enabled until the line under voltage
lock out limit is reached. At that point, once the FB pin
has reached above 600mV, the output driver is enabled.
As the output voltage starts to increase, the error signal
from the error amplifier starts to decrease. If isolation is
required, the error amplifier output can drive the LED of
the opto isolator. The output of the opto is connected in
a common emitter configuration with a pull up resistor to
a reference voltage connected to the FB pin of the
SC4905. The voltage level at the FB pin provides the duty
cycle necessary to achieve regulation.
2006 Semtech Corp.
11
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