PM6680 STMicroelectronics, PM6680 Datasheet - Page 39

• 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

PM6680
The T node voltage is the sum of the output voltage and the triangular waveform generated
by the virtual ESR network. In fact the virtual ESR network behaves like a further equivalent
ESR R
A good trade-off is to design the network in order to achieve an R
Equation 28
where ∆I
voltage. It should be chosen higher than approximately 30 mV.
The new closed loop gain depends on C
that:
Equation 29
Where:
Equation 30
where R
given by the virtual ESR network R
Moreover C
Equation 31
Where k is a free design parameter greater than 3 and determines the minimum integrator
capacitor value C
Equation 32
C must be selected as shown:
Equation 33
ESR
TOT
L
is the inductor current ripple and V
.
INT
is the sum of the ESR of the output capacitor Rout and the equivalent ESR
must meet the following condition:
INT
:
f
C
sw
INT
>
C
ESR
R
f
Z
k
INT
>
ESR
×
=
2
.
f
π
C
>
2
Z
INT
=
π
×
2
=
>
V
×
⎛
⎜ ⎜
⎝
. In order to ensure stability it must be verified
π
g
g
RIPPLE
5
2
f
C
sw
∆
RIPPLE
k
×
m
m
π
×
I
out
L
f
×
Z
C
1
−
C
INT
×
×
f
Z
−
out
R
V
⎞
⎟ ⎟
⎠
k
is the overall ripple of the T node
R
Vr
TOT
OUT
×
×
out
V
R
Vr
OUT
TOT
ESR
given by:
Device description
39/49