PM6680A STMicroelectronics, PM6680A Datasheet - Page 26

• Manufacturer Part Number: PM6680A
• Description: IC CTLR DUAL SYNC STDN 5X5VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680A

• Applications: Controller, Embedded Computer System
• Voltage - Input: 6 ~ 36 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• For Use With: 497-6379 - BOARD EVALUATION FOR PM6680A497-6378 - BOARD EVALUATION FOR PM6680497-6425 - BOARD EVAL BASED ON PM6680A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Device description
7.8
26/48
Figure 35. Soft start waveforms
When a switching section is turned off (EN1/EN2 pins low), the controller enters in soft end
mode.The output capacitor is discharged through an internal 18 Ω p-MOSFET switch; when
the output voltage reaches 0.3 V, the low-side MOSFET turns on, keeping the output to
ground. The soft end time also depends on load condition.
Gate drivers
The integrated high-current drivers allow to use different power MOSFETs. The high side
driver MOSFET uses a bootstrap circuit which is indirectly supplied by LDO5 output. The
BOOT and PHASE pins work respectively as supply and return rails for the HS driver.
The low side driver uses the internal LDO5 output for the supply rail and PGND pin as return
rail.
An important feature of the gate drivers is the adaptive anti-cross conduction protection,
which prevents high side and low side MOSFETs from being on at the same time. When the
high side MOSFET is turned off the voltage at the phase node begins to fall. The low side
MOSFET is turned on when the voltage at the phase node reaches an internal threshold.
When the low side MOSFET is turned off, the high side remains off until the LGATE pin
voltage goes approximatively under 1 V.
The power dissipation of the drivers is a function of the total gate charge of the external
power MOSFETs and the switching frequency, as shown in the following equation:
Equation 11
Where V
driver
is the 5 V driver supply.
P
driver
=
V
driver
×
Q
g
×
f
SW
PM6680A