NCP1081DER2G ON Semiconductor, NCP1081DER2G Datasheet - Page 16

• Manufacturer Part Number: NCP1081DER2G
• Description: IC CONV CTLR POE-PD 40W 20-TSSOP
• Manufacturer: ON Semiconductor
• Type: Power over Ethernet Switch (PoE)r

Specifications of NCP1081DER2G

• Applications: Remote Peripherals (Industrial Controls, Cameras, Data Access)
• Internal Switch(s): Yes
• Current Limit: 1.1A
• Voltage - Supply: 0 V ~ 57 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP Exposed Pad, 20-eTSSOP, 20-HTSSOP
• Output Voltage: 9 V
• Switching Frequency: 250 KHz
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Output Power: 40 W
• Input Voltage: 57V
• Supply Current: 510mA
• Digital Ic Case Style: TSSOP
• No. Of Pins: 20
• Duty Cycle (%): 80%
• Uvlo: 38V
• Frequency: 500kHz
• Svhc: No SVHC (20-Jun-2011)
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Current Limit Comparator
senses the current flowing in the external MOSFET for
current mode control and cycle−by−cycle current limit. This
is performed by the current limit comparator which, on the
CS pin, senses the voltage across the external Rcs resistor
located between the source of the MOSFET and the ARTN
pin.
CS pin which ensures that the current limit and PWM
comparators are not prematurely trigged by the current spike
that occurs when the switching MOSFET turns on.
Slope Compensation Circuitry
problems that exist with converters running in continuous
The NCP1081 current limit block behind the CS pin
The NCP1081 also provides a blanking time function on
To overcome sub−harmonic oscillations and instability
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conduction mode (CCM) and when the duty cycle is close
or above 50 percent, the NCP1081 integrates a current slope
compensation circuit. The amplitude of the added slope
compensation is typically 110 mV over one cycle.
250 kHz, the internal slope provided by the NCP1081 is
27.5 mV/mA typically.
DC−DC Controller Oscillator
inserted between OSC and ARTN, and is defined by the
following equation:
As an example, for an operating switching frequency of
The frequency is configured with the Rosc resistor
The duty cycle limit is fixed internally at 80 percent.
R
OSC
(kW) +
F
OSC
38600
(kHz)