AR2003FV

3 of 15

December 2014

Document number: DS37473 Rev. 3 - 2

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AR2003FV

Pin Descriptions

Pin Number

Pin Name

Function

1, 7

NC

Not Connected

2

TON

Minimum On-time Setting Pin

3

AGND

This is the ground reference for all internal comparators and thresholds.

4

TOFF/EN

Enable Pin/ Minimum Off-time

This pin combines the functions of setting the programmable minimum off-time as well as acting as the

enable pin. The device enters Under Voltage Lock Out (UVLO) mode when VCC falls below the UVLO

threshold. At this point the TOFF/EN pin is internally shorted to ground through a resistor. The internal

current source (used for setting TOFF) is powered down. Once the UVLO threshold is exceeded, the internal

resistance is removed and the current source is activated. If the voltage applied to the TOFF/EN pin exceeds

the VENON threshold then the device is in Active Mode. If the voltage drops below the VENOFF threshold then

the device is in Sleep Mode.

5

SFB

Output pin of internal feedback resistor which is connected to VCC. It is sent to TL431 (or its compatible) to

drive the opto-coupler and provide feedback voltage to primary side controller to realize Secondary

Synchronous Rectification.

6

OVS

Output voltage (VCC) select pin, work together with SFB to select output voltage in 5V or 12V.

8

VS

This is the connection to internal MOSFET Source. VS is also connected to GND.

9, VD pad

VD

This is a connection to the internal MOSFET Drain. The pin needs to be connected as closely as possible to

the transformer used in the application, to minimize the effects of parasitic inductance on the performance of

the device. The device requires that VD has a voltage greater than 1.5V and that the TOFF timer has expired

before the MOSFET is able to be activated. Once these conditions are met and the voltage internally sensed

on the VD pin is 150mV lower than the VS pin, the internal MOSFET is turned on and the TON minimum on

time period is started. The MOSFET will remain on for at least the length of the minimum on time. The only

thing that can override this is if a pulse is detected on the SNYC pin. After the TON period, the MOSFET

remains on until the VD to VS voltage has reached to the VTHOFF threshold, at which point the internal

MOSFET is turned off. As mentioned before, if the VTHOFF threshold is reached before the TON period has

expired, the device will enter the Light Load Mode. Under this mode, the MOSFET will not be turned on the

next switching cycle. When the drain voltage has increased to 1.5V, the TOFF timer is triggered, during

which the MOSFET is prevented from turning on.

10

GATE

Connect GATE to the gate of the controlled MOSFET through a small series resistor using short PC board

tracks to achieve optimal switching performance. The GATE output can achieve >2-A peak source current

when High and >4-A peak sink current when Low into a large N-channel power MOSFET.

11

SYNC

If a falling edge is sensed on this pin, the internal MOSFET is immediately turned off, irrespective of the

sensed drain to source voltage or the state of the TON timer. This characteristic allows the device to be

easily used in a Continuous Conduction Mode (CCM) system. The SYNC pin needs to be connected to a

suitable control signal on the primary side of the convertor, using a high voltage isolation cap, transformer or

other suitable means.

12

DGATE

During Over Voltage Protection, DGATE will drive external MOSFET to pull down the output voltage so that

Primary side controller will start the Short Circuit Protection handling.

13

GND

This is the reference potential for all internal comparators and thresholds.

14

VCC

VCC supplies all the internal circuitry of the device. A DC supply is required to be connected to this pin. It is

required that a 10µF or larger capacitor is placed between this pin and GND, as close to the pins as possible.

The device will not function until the VCC has risen above the UVLO threshold. The device can safely be

turned off by bringing VCC below the UVLO threshold (minus the UVLO threshold hysteresis). If VCC drops

below the UVLO threshold (minus UVLO threshold hysteresis), the MOSFET is turned off and the TOFF/EN

pin is internally connected to GND.