SM72295_15 Datasheet, PDF (10/17 Pages) Texas Instruments – SM72295 Photovoltaic Full Bridge Driver

SM72295
SNVS688E – OCTOBER 2010 – REVISED APRIL 2013
Figure 14. Diode Power Dissipation V_IN = 50V
0.100
0.010
C_L = 4400 pF
C_L = 0 pF
www.ti.com
0.001
1
10
100
1000
SWITCHING FREQUENCY (kHz)
Layout Considerations
The optimum performance of high and low-side gate drivers cannot be achieved without taking due
considerations during circuit board layout. Following points are emphasized.
1. Low ESR / ESL capacitors must be connected close to the IC, between VDD and VSS pins and between the
HB and HS pins to support the high peak currents being drawn from VDD during turn-on of the external
MOSFET.
2. To prevent large voltage transients at the drain of the top MOSFET, a low ESR electrolytic capacitor must be
connected between MOSFET drain and ground (VSS).
3. In order to avoid large negative transients on the switch node (HS pin), the parasitic inductances in the
source of top MOSFET and in the drain of the bottom MOSFET (synchronous rectifier) must be minimized.
4. Grounding Considerations:
(a) The first priority in designing grounding connections is to confine the high peak currents that charge and
discharge the MOSFET gate into a minimal physical area. This will decrease the loop inductance and
minimize noise issues on the gate terminal of the MOSFET. The MOSFETs should be placed as close as
possible to the gate driver.
(b) The second high current path includes the bootstrap capacitor, the bootstrap diode, the local ground
referenced bypass capacitor and low-side MOSFET body diode. The bootstrap capacitor is recharged on
a cycle-by-cycle basis through the bootstrap diode from the ground referenced VDD bypass capacitor.
The recharging occurs in a short time interval and involves high peak current. Minimizing this loop length
and area on the circuit board is important to ensure reliable operation.
10
Submit Documentation Feedback
Product Folder Links: SM72295
Copyright © 2010–2013, Texas Instruments Incorporated