PM6685 STMicroelectronics, PM6685 Datasheet - Page 23
PM6685
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
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Manufacturer
Quantity
Price
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Part Number:
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PM6685
7.5
7.6
Figure 31. PWM and pulse skip mode inductor current
No-audible skip mode
If SKIP pin is tied to V
kHz is enabled. At light load condition, If there is not a new switching cycle within a 30 µs
(typ.) period, a no-audible skip mode cycle begins.
Figure 32. Frequency clamp skip mode
The low side switch is turned on until the output voltage crosses about Vreg+1%. Then the
high side MOSFET is turned on for a fixed on time period. Afterwards the low side switch is
enabled until the inductor current reaches the zero-crossing threshold. This keeps the
switching frequency higher than 33 kHz. As a consequence of the control, the regulated
voltage can be slightly higher than Vreg (up to 1%).
If, due to the load, the frequency is higher than 33 kHz, the device works like in skip mode.
No-audible skip mode reduces audio frequency noise that may occur in pulse skip mode at
very light loads, keeping the efficiency higher than in PWM mode.
Current limit
The current-limit circuit employs a “valley” current-sensing algorithm. During the conduction
time of the low side MOSFET the current flowing through it is sensed. The current-sensing
element is the low side MOSFET
REF
, a no-audible skip mode with a minimum switching frequency of 33
Doc ID 11674 Rev 8
on-resistance(Figure
33)
Device description
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