VIPER37HE STMicroelectronics, VIPER37HE Datasheet - Page 23

• Manufacturer Part Number: VIPER37HE
• Description: AC/DC Switching Converters ViperPlus Fixed Freq 800V 30mQ 265 Vac
• Manufacturer: STMicroelectronics
• Type: Off Line Switcherr

Specifications of VIPER37HE

• Product Category: AC/DC Switching Converters
• Rohs: yes
• Input / Supply Voltage (max): 23.5 V
• Input / Supply Voltage (min): 8.5 V
• Switching Frequency: 115 kHz
• Supply Current: 3.5 mA
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: Through Hole
• Package / Case: SDIP-10
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 25 C
• Number Of Outputs: 1
• Output Power: 25 W

VIPER37
8.6
8.7
Figure 27. Timing diagram: behavior after short-circuit
Oscillator
The switching frequency is internally fixed to 60 kHz or 115 kHz. In both cases the switching
frequency is modulated by approximately ±4 kHz (60 kHz version) or ±8 kHz
(115 kHz version) at a 250 Hz (typ.) rate, so that the resulting spread-spectrum action
distributes the energy of each harmonic of the switching frequency over a number of side-
band harmonics having the same energy on the whole but smaller amplitudes.
Current mode conversion with adjustable current limit set
point
This device is a current mode converter: the drain current is sensed and converted into
voltage that is applied to the non-inverting pin of the PWM comparator. This voltage is
compared with the one on the feedback pin through a voltage divider on a cycle-by-cycle
basis.
The device has a default current limit value, I
electrical specifications, through the R
Figure 16
The CONT pin has a minimum current sunk, needed to activate the I
R
Table 8
LIM
or with high R
).
).
LIM
(i.e. 100 kΩ), the current limit is fixed to the default value (see I
Doc ID 022218 Rev 1
LIM
resistor connected to the CONT pin (see
Dlim
, that the user can adjust according to the
Dlim
Operation description
adjustment: without
Dlim
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