PM6680ATR STMicroelectronics, PM6680ATR Datasheet - Page 40

• Manufacturer Part Number: PM6680ATR
• Description: IC CTRLR DUAL STEP DOWN 32VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680ATR

• 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
• Other names: 497-6896-2; PM6680ATR

Design guidelines
9.8
40/48
Figure 40. Bootstrap circuit
The bootstrap circuit capacitor value C
side MOSFET during turn on phase. A typical value is 100 nF.
The bootstrap diode D must charge the capacitor during the off time phases. The maximum
rated voltage must be higher than V
A resistor R
node rises up, working like a gate resistor for the turn on phase of the high side MOSFET.
Design example
The following design example considers an input voltage from 16 V to 32 V(the typical value
is 24 V). The two switching outputs are OUT1 = 3.3 V and OUT2 = 1.8 V and must deliver a
maximum current of 2.5 A. The selected switching frequencies are about 290 kHz for OUT1
section and about 440 kHz for OUT2 section (see
1.
OUT1: ILOAD = 2.5 A, 45 % ripple current.
Equation 36
We choose standard value L= 8.2 µH.
∆I
I
I
OUT2:ILOAD=2.5 A, 35 % ripple current.
LRMS
peak
L(max)
Inductor selection
= 2.5 A + 0.58 A = 3.83 A
= 2.523 A
= 1.16 A @VIN = 24 V.
BOOT
on the BOOT pin could be added in order to reduce noise when the phase
L
L
INmax
BOOT
C
C
.
R
R
B
B
O
B
B
O
must provide the total gate charge to the high
O
O
O
O
O
O
T
T
D
D
T
T
B
P
B
P
Table 6
O
H
H
O
L
L
A
A
O
O
D
D
S
S
T
T
O
O
E
E
5
5
).
PM6680A