PM6685 STMicroelectronics, PM6685 Datasheet - Page 41

• Manufacturer Part Number: PM6685
• Description: IC CTLR DUAL SYNC STDN 5X5VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6685

• Applications: Controller, Notebook Power System
• Voltage - Input: 6 ~ 28 V
• Number Of Outputs: 2
• Voltage - Output: -3.3V, 5V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• Output Voltage: 5 V, 3.3 V
• Output Current: 0.1 A
• Input Voltage: 5.5 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 10 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PM6685
10
10.1
10.2
10.3
Design example
The following design example considers an input voltage from 7 V to 16 V. The two switching
outputs must deliver a maximum current of 5A. The selected switching frequencies are 200
kHz for the 5 V section and 300 kHz for the 3.3 V section.
Inductor selection
OUT5: I
Equation 34
We choose standard value L = 6 µH
ΔI
I
I
OUT3: ILOAD = 5 A, 50% ripple current.
Equation 35
We choose standard value L=4 µH.
ΔI
I
I
Output capacitor selection
We would like to have an output ripple greater than 35mV.
OUT5: POSCAP 6TPB330M
OUT3: POSCAP 6TPB330M
Power MOSFETs
OUT5: High side: STS12NH3LL
OUT3: High side: STS12NH3LL
LRMS
peak
LRMS
peak
L(max)
L(max)
= 5 A + 0.95 A = 6.43 A
= 5 A + 1.1 A = 6.1 A
= 5.07 A
= 5.04 A
Low side: STS12NH3LL
LOAD
= 2.86 A @V
= 2.2 A @V
= 5 A, 60% ripple current.
IN
IN
=16 V
=16 V
L
L
Doc ID 11674 Rev 8
=
=
300
200
. 3
5
KHz
33
KHz
V
⋅
⋅
(
(
16
16
⋅
⋅
16
16
V
−
V
V
−
. 3
⋅
⋅
5
0
33
0
) V
5 .
6 .
)
⋅
⋅
5
5
≈
≈
. 3
5
7 .
52
μ
μ
H
H
Design example
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