Features Fixed 60kHz switching frequency
9 V to 38 V Wide Range VDD Voltage Current Mode Control Auxiliary Undervoltage Lockout with Hysteresis High Voltage Startup Current Source SO-8 DIP-8
Over-temperature, over-current, and over-voltage typical applications include offline power protection, battery charger adapter auto-restart, backup power supply Typical power for TVs or monitors, auxiliary power Europe (195-265 VAC) 8 watts, for SO- 8. Motor control, etc.
13 W For DIP-8, internal control circuit provides the following European (85-265 VAC) 5 W for SO-8, Advantages: Large input voltage range on VDD pin 8 W for DIP-8 to accommodate changes in auxiliary power .
voltage (this feature is ideal for battery specification charger adapter configurations), automatic burst under load and overvoltage modes Viper12A combines dedicated current protection in Hiccup mode.
High voltage power mode PWM controller MOSFET on the same silicon chip.
Figure 1. Block Diagram

Electrical Data Maximum Ratings Above the ratings listed in the Absolute Maximum Ratings table Stress applied to the device may cause permanent damage to the equipment. These are only pressure ratings and the device under these or any other conditions is not implied by this specification. Exposure to absolute maximum rated conditions for extended periods of time may affect device reliability.

Table 9. Pin Function Pin Names Pin Function Controls the power supply of the circuit. Charge current is also provided at startup thanks to a high voltage current source connected to the drain. To do this, a hysteretic comparator monitors the VDD voltage and provides two thresholds: vdd-vddon: the voltage value at which the device starts switching and spinning (typically 14.5 V)
Turn off the startup current source.
-vddoff: The voltage value at which the device stops switching and turns on (usually 8 V)
Start the current source.

Source Power MOSFET source and circuit ground reference.
Power FET drain. During the drain start-up phase, the internal high voltage current source is also used to charge the external VDD capacitor.
Feedback input. The valid voltage range extends from 0 V to 1 V and defines the FB peak drain MOSFET current. Current limit, corresponding to the maximum leakage current obtained when the FB pin is shorted to the power supply pin.

Rectangular UI Output Characteristics Rectangular UI Output Characteristics for Battery Chargers A complete adjustment scheme enables combined and precise output characteristics.
Secondary feedback is provided through an optocoupler driven by the TSM101 . This device provides two op amps and a voltage reference, allowing the output voltage and current to be regulated. An integrated OR function performs two resulting error signals, resulting in double voltage and current limiting, known as the rectangular output characteristic. This power source is particularly useful for battery chargers, whose output is primarily used in the current mode in order to provide charging rates. Precise voltage regulation also facilitates the need for two modes of operation for Li-ion batteries.

Wide voltage range for vdd' The voltage range of the vdd pin extends from 9 V to V 38. This feature provides a variety of behaviors in the flexibility of the design implementation. In understanding the configuration on page C 4 7 the options have been proposed to supply the device with Two benefits: At the start of fast device switching, it immediately receives some energy from auxiliary winding. C5 can lower therefore and a small ceramic chip (100 NF) sufficient to insure the filtering function. In total, start time from switch on Input voltage to output voltage presence also decreased dramatically.
The synchronous output current characteristic can be maintained even with very low or zero output voltage. Since the "tsm101 is also supplied in forward mode, it makes the current regulation on what the output voltage is." The voltage of the vdd pin may be multi-century or more than the input voltage, that is to say with a ratio of about 4 parts of a wide range of application.

How the Feedback Pin Works The feedback pin controls the operation of the device. Unlike conventional PWM control circuits that use the voltage input (the inverting input of the op amp) and the FB pin are sensitive to current. Figure 5. shows the internal current mode structure.
The internal current control structure power MOSFET provides an induced current proportional to the main current ID.
R2 receives this current and the current from the FB pin. The voltage on R2 is then compared to a fixed reference voltage of 0.23 V. Turn off the MOSFET. When the following equation is reached:

Current limit is obtained by shorting the FB pin to ground (VFB=0 V). This leads to the negative current supplied by this pin and is expressed by the following formula: In practical applications, the FB pin is driven by an optocoupler to act as an emergency stop. So, it's not possible to actually short this pin to ground and the drain above.
The current value is not achievable. Nevertheless, capacitor C is at the average energized voltage at the FB pin, and when the optocoupler is turned off (started or shorted), the corresponding voltage can be assumed to be very close to 0 volts.
For low leakage current, equation (1) is valid as long as ifb satisfies ifb cycle. This is especially important when the converter is lightly loaded.
IFB transfer function

The overall DC transfer function can then be established between ID and IFB as shown.
This figure also takes into account the internal blanking time and its associated minimum turn-on time. This imposes a minimum leakage current at which the device cannot control it in a linear fashion. This leakage current depends on the inductance value of the primary current transformer and the input voltage. Two things can happen, depending on how this current value compares to the fixed 50 mA value, as described above.

Startup sequence Figure 7. Startup sequence The device consists of a connection to the device. Once a voltage is applied to the input of the converter, this startup current activates the source as long as vdd is lower than vddon. When vddon is reached, the startup current source is turned off and the device begins to operate by turning its main power supply on and off.
Power Field Effect Transistor. Since the FB pin does not receive any current from the optocoupler, the device operates at full current capacity and the output voltage rises until it reaches the regulation point where the secondary loop starts sending current in the optocoupler. AT At this point, the converter enters a regulation operation in which the FB pin receives the current required to provide the correct supply on the secondary side.

Note that during the actual startup phase, the TSS consumes some energy from the VDD capacitor, waiting for a continuous supply from the auxiliary winding. If the value of this capacitor is too low, the startup phase is terminated.
It must not be started until any energy has been received from the auxiliary winding and the converter.
This is also illustrated in the same figure in dashed lines.

Over voltage threshold
An overvoltage detector on the VDD pin allows the Viper12A to reset itself at VDD.
over vddovp.
overvoltage event. Note that this event is only locked for the time required for VDD to arrive. The device then automatically resumes normal operation.