PM6680 STMicroelectronics, PM6680 Datasheet - Page 42

• Manufacturer Part Number: PM6680
• Description: IC CTRLR DUAL STEP DOWN 32VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680

• Applications: Controller, Notebook Power System
• Voltage - Input: 6 ~ 28 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 5.5 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• Output Voltage: 5 V, 0.9 V to 5.5 V, 0.9 V to 3.3 V
• Output Current: 0.33 A
• Input Voltage: 5.5 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 10 C
• 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
7.13.8
42/49
Design example
The following design example considers an input voltage from 7 V to 16 V. The two switching
outputs are OUT1=1.5 V and OUT2=1.05 V and must deliver a maximum current of 5 A. The
selected switching frequencies are about 290 kHz for OUT1 section and about 425 kHz for
OUT2 section (see
1.
Equation 36
Equation 37
2.
3.
4.
Equation 38
Inductor selection
OUT1: I
We choose standard value L = 2.5 uH.
∆I
I
I
OUT2: I
∆I
I
I
Output capacitor selection
We would like to have an output ripple smaller than 25 mV.
OUT1: POSCAP 6TPB330M
OUT2: POSCAP 6TPB330M
Power MOSFETS
OUT1: High side: STS12NH3LL
Low side: STS12NH3LL
OUT2:High side: STS12NH3LL
Low side: STS12NH3LL
Current limit
OUT1:
LRMS
PEAK
LRMS
PEAK
L(max)
L(max)
= 5 A + 0.9 A = 5.9 A
= 5 A + 0.8 A = 5.8 A
= 5.03 A
= 5.02 A
LOAD
LOAD
= 1.8 A @V
= 1.6 A @V
= 5 A, 35 % ripple current.
= 5 A, 30 % ripple current.
Table 7 on page 30
I
IN
IN
Lvalley
=12 V
= 12 V.
L
L
(min)
=
=
290
. 1
425
1
05
5 .
=
KHz
KHz
V
V
I
LOAD
).
⋅
⋅
(
(
16
⋅
16
⋅
16
16
(max)
V
V
V
V
−
−
⋅
⋅
1
. 1
. 0
0
5 .
−
05
35
3 .
) V
∆
) V
⋅
I
⋅
5
L
5
(min)
2
≈
≈
1
2
6 .
5 .
=
µ
µ
H
. 4
H
12
A
PM6680