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VIPER26HDTR-VIPER26LDTR
Energy saving VIPer Plus: 12W high voltage converter with direct feedback
September 2010 Doc ID 17736 Rev 2 1/25
VIPER26Fixed frequency VIPer TM plus family
Features 800 V avalanche rugged power section PWM operation with frequency jittering for low
EMI Operating frequency: 60 kHz for L type 115 kHz for H type Standby power < 50 mW at 265 VAC Limiting current with adjustable set point On-board soft-start Safe auto-restart after a fault condition Hysteretic thermal shutdown
Application Auxiliary power supply for appliances Power metering LED drivers SMPS for set-top boxes, DVD players and
recorders
DescriptionThe device is an off-line converter with an 800 V
avalanche ruggedness power section, a PWM
controller, user defined overcurrent limit,
protection against feedback network
disconnection, hysteretic thermal protection, soft
start up and safe auto restart after any fault
condition.
Advance frequency jittering reduces EMI filter
cost. Burst mode operation and the devices very
low consumption both help to meet the standard
set by energy saving regulations.
Figure 1. Typical topology (VOUT ≤ VDDCSon)
Table 1. Device summary
Contents VIPER262/25 Doc ID 17736 Rev 2
Contents Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Typical power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Typical circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Power section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 High voltage current generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Soft start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Adjustable current limit set point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 FB pin and COMP pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Automatic auto restart after overload or short-circuit . . . . . . . . . . . . . 17 Open loop failure protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
VIPER26 Block diagram
Doc ID 17736 Rev 2 3/25
1 Block diagram
2 Typical power
Figure 2. Block diagram
Table 2. Typical power Typical continuous power in non ventilated enclosed adapter measured at 50 °C ambient. Maximum practical continuous power in an open frame design at 50 °C ambient, with adequate heat
sinking.
Pin settings VIPER26
4/25 Doc ID 17736 Rev 2
3 Pin settings
Figure 3. Connection diagram (top view)
Note: The copper area for heat dissipation has to be designed under the DRAIN pins.
Table 3. Pin description
VIPER26 Electrical data
Doc ID 17736 Rev 2 5/25
4 Electrical data
4.1 Maximum ratings
4.2 Thermal data
Table 4. Absolute maximum ratings
Table 5. Thermal data When mounted on a standard single side FR4 board with 100 mm2 (0.155 sq in) of Cu (35 µm thick)
Electrical data VIPER26
6/25 Doc ID 17736 Rev 2
4.3 Electrical characteristics
(TJ = -25 to 125 °C, VDD = 14 V (a) ; unless otherwise specified)
Adjust VDD above VDDon startup threshold before setting to 14 V
Table 6. Power section
Table 7. Supply section
VIPER26 Electrical data
Doc ID 17736 Rev 2 7/25
Table 8. Controller section
Typical electrical characteristics VIPER26
8/25 Doc ID 17736 Rev 2 Typical electrical characteristics
Figure 4. IDlim vs TJ Figure 5. FOSC vs TJ
Figure 6. V DRAIN_START vs TJ Figure 7. H COMP vs TJ
Figure 8. GM vs TJ Figure 9. V REF_FB vs TJ
VIPER26 Typical electrical characteristics
Doc ID 17736 Rev 2 9/25
Figure 10. ICOMP vs TJ Figure 11. Operating supply current
(no switching) vs TJ
Figure 12. Operating supply current
(switching) vs TJ
Figure 13. IDlim vs RLIM
Figure 14. Power MOSFET on-resistance vs TJ Figure 15. Power MOSFET break down voltage
vs TJ
Typical circuits VIPER26
10/25 Doc ID 17736 Rev 2
Figure 16. Thermal shutdown
6 Typical circuits
Figure 17. Buck converter (V>V)
VIPER26 Typical circuits
Doc ID 17736 Rev 2 11/25
Figure 18. Fly-back converter (isolated)
Figure 19. Flyback converter (primary regulation)
Typical circuits VIPER26
12/25 Doc ID 17736 Rev 2
Figure 20. Flyback converter (non isolated, VOUTmVDDCSon)
Figure 21. Flyback converter (non isolated, V OUT[V DDCSon)
VIPER26 Power section
Doc ID 17736 Rev 2 13/25
7 Power section
The power section is implemented with an n-channel power MOSFET with a breakdown
voltage of 800 V min. and a typical RDS(on) of 7 Ω . It includes a SenseFET structure to allow
a virtually lossless current sensing and the thermal sensor.
The gate driver of the power MOSFET is designed to supply a controlled gate current during
both turn-ON and turn-OFF in order to minimize common mode EMI. During UVLO
conditions, an internal pull-down circuit holds the gate low in order to ensure that the power
MOSFET cannot be turned ON accidentally. High voltage current generator
The high voltage current generator is supplied by the DRAIN pin. At the first start up of the
converter, it is enabled when the voltage across the input bulk capacitor reaches the
VDRAIN_START threshold, sourcing the IDDch1 current (see Table 7 on page 6); as the VDD
voltage reaches the VDDon start-up threshold, the power section starts switching and the
high voltage current generator is turned OFF. The VIPer26 is powered by the external
source. After the start-up, the auxiliary winding or the diode connected to the output voltage
have to power the VDD capacitor with voltage higher than VDDCSon threshold (see Table7
on page 6). During the switching, the internal current source is disabled and the
consumptions are minimized. In case of fault the switching is stopped and the device is self
biased by the internal high voltage current source; it is activated between the levels VDDCSon
and VDDon delivering the current IDDch2 to the VDD capacitor during the MOSFET off time,
see Figure 22 on page 13.
At converter power-down, the VDD voltage drops and the converter activity stops as it falls
below VDDoff threshold (see Table 7 on page 6).
Figure 22. Power on and power off
