PM6685 STMicroelectronics, PM6685 Datasheet - Page 31

• 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
8.8
where fsw is the switching frequency, VIN is the input voltage, VOUT is the output voltage
and ΔIL is the selected inductor ripple current.
In order to prevent overtemperature working conditions, inductor must be able to provide an
RMS current greater than the maximum RMS inductor current ILRMS:
Equation 11
Where ΔIL(max) is the maximum ripple current:
Equation 12
If hard saturation inductors are used, the inductor saturation current should be much greater
than the maximum inductor peak current Ipeak:
Equation 13
Using soft saturation inductors it’s possible to choose inductors with saturation current limit
nearly to Ipeak.
Below there is a list of some inductor manufacturers.
Table 11.
Output capacitor
The selection of the output capacitor is based on the ESR value Rout and the voltage rating
rather than on the capacitor value Cout.
The output capacitor has to satisfy the output voltage ripple requirements. Lower inductor
value can reduce the size of the choke but increases the inductor current ripple ΔIL.
Since the voltage ripple VRIPPLEout is given by:
Equation 14
Manufacturer
COILCRAFT
COILCRAFT
TDK
Inductor manufacturer
RLF12560
SER1360
Series
MLC
I
LRMS
Δ
I
Doc ID 11674 Rev 8
Ipeak
L
Inductor value (µH) RMS current (A) Saturation current (A)
(max)
=
V
I (
2.2 to 4.5
2.7 to 10
RIPPLEout
=
LOAD
4 to 8
=
I
LOAD
V
IN
(max))
max
(max)
f
sw
=
−
×
R
2
L
V
out
+
OUT
+
×
Δ
(
Δ
I
Δ
L
×
I
13.6 to 8.8
7.5 to 11.5
I
(max)
L
L
2
(max))
V
6 to 8.6
12
V
IN
OUT
max
Monitoring and protections
2
7.5 to 14.4
11.5 to 17
7 to 12
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