STEVAL-ISA035V1 STMicroelectronics, STEVAL-ISA035V1 Datasheet - Page 11

• Manufacturer Part Number: STEVAL-ISA035V1
• Description: BOARD EVAL BASED ON VIPER22A
• Manufacturer: STMicroelectronics
• Series: VIPER™r
• Type: Other Power Managementr

Specifications of STEVAL-ISA035V1

• Mfg Application Notes: VIPer12/22A-E AppNote
• Main Purpose: AC/DC, Non-Isolated
• Outputs And Type: 1, Non-Isolated
• Power - Output: 4.2W
• Voltage - Output: 12V
• Current - Output: 350mA
• Voltage - Input: 85 ~ 264VAC
• Regulator Topology: Buck
• Frequency - Switching: 60kHz
• Board Type: Fully Populated
• Utilized Ic / Part: VIPer22A
• Input Voltage: 85 V to 264 V
• Output Voltage: 12 V
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: VIPER22A-E
• Other names: 497-8215

AN2544
1.7
Figure 8.
The VIPer internal 1 mA current source charges up the V
the V
raising the output voltage to the point of bootstrapping. The V
the energy to supply the necessary output current and to charge up the output capacitor,
before the V
9 V).
under a resistive load of 350 mA.
In
capacitor does not store enough energy. As seen the output voltage (green trace) does not
reach high enough to bootstrap, It succeeds the second time after there is a partial charge
on the output cap.
supply starts the first time.
Burst mode in no-load or very light load
At very light load, the on-time becomes so small that some pulses are skipped in order to
stay in regulation and meet energy requirements such as Blue Angel or Energy Star. This
mode is called burst mode. It skips as many cycles as needed to maintain regulation. In the
case below at no-load about 9 cycles are skipped to maintain an output.
Bad start
Figure 8
dd
Figure 8
pin reaches the V
the purple trace is the V
dd
and
voltage falls below the V
9
Figure 9
show a V
dd
is using a 4.7 µF V
startup threshold (Worse case is 13 V) the VIPer starts pulsing,
dd
cap that is not large enough to start up the evaluation board
dd
voltage rising to ~14 V. The energy with the 2.2 µF
dd
Figure 9.
under voltage shutdown threshold (worse case is
dd
cap. With adequate energy the power
Good start
dd
capacitor. When the voltage on
dd
capacitor needs to supply
Circuit operation
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