PM6686 STMicroelectronics, PM6686 Datasheet - Page 42

• Manufacturer Part Number: PM6686
• Description: Dual Step-down Controller With Adjustable Voltages, Adjustable Ldo And Auxiliary Charge Pump Controller For Notebook
• Manufacturer: STMicroelectronics

Diode selection
11
11.1
11.2
42/50
Diode selection
Freewheeling diode
A rectifier across the low-side MOSFET is recommended. The rectifier works as a voltage
clamp across the synchronous rectifier and reduces the negative inductor swing during the
dead time between turning the high-side MOSFET off and the synchronous rectifier on. It
can increase the efficiency of the switching section, since it reduces the low-side switch
losses. A Schottky diode is suitable for its low forward voltage drop (0.3 V). The diode
reverse voltage must be greater than the maximum input voltage. A minimum recovery
reverse charge is preferable. Below there is a list of some Schottky diode manufacturers.
Table 20.
Charge pump diode
The charge pump capacitors are fed by the current supplied by LGATE1 (output of the low-
side driver for the section 1). Dual in package diodes, in series configuration, could be used
to reduce the area occupation.
Table 21.
Manufacturer
Manufacturer
ST
ST
ST
ST
ST
Schottky diode manufacturer
Schottky diode manufacturer
STPS1L30M
STPS1L20M
BAS69-04
BAR43A
BAT54S
Series
Series
Doc ID 15281 Rev 4
Forward voltage
Forward voltage
0.34
0.37
0.24
0.35
0.35
(V)
(V)
Rated reverse
Rated reverse
voltage (V)
voltage (V)
40
30
30
20
15
Reverse current
Max forward
current (A)
0.000075
0.00039
0.01
(μA)
0.3
0.1
PM6686