PM6685_07 Datasheet, PDF (1/52 Pages) STMicroelectronics – Dual step-down main supply controller with auxilary voltages for notebook system power

PM6685
Dual step-down main supply controller
with auxilary voltages for notebook system power
Features
■ 6V to 28V input voltage range
■ Fixed 5V - 3.3V output voltages
■ 5V and 3.3V voltage always available to deliver
100mA of peak current
■ 1.237V ±1% reference voltage available
■ Lossless current sensing using low side
■ MOSFETs' R_DS(on)
■ Negative current limit
■ Soft-start internally fixed at 2ms
■ Soft output discharge
■ Latched OVP and UVP
■ Selectable pulse skipping at light loads
■ Selectable minimum frequency (33kHz) in
pulse skip mode
■ 4mW maximum quiescent power
■ Independent power good signals
■ Output voltage ripple compensation
Applications
■ Notebook computers
■ Tablet PC or slates
■ Mobile system power supply
■ 3 and -4 Cells Li+ battery-powered devices
VFQFPN-32 (5mm x 5mm)
Description
PM6685 is a dual step-down controller specifically
designed to provide extremely high efficiency
conversion with loss-less current sensing
technique. The constant on-time architecture
assures fast load transient response and the
embedded voltage feed-forward provides nearly
constant switching frequency operation.
An embedded integrator control loop
compensates the DC voltage error due to the
output ripple. The pulse skipping technique
increases efficiency for very light loads. Moreover,
a minimum switching frequency of 33kHz is
selectable in order to avoid audio noise issues.
The PM6685 provides a selectable switching
frequency, allowing either 200kHz/300kHz,
300kHz/400kHz, or 400kHz/500kHz operation of
the 5V/3.3V switching sections.
Table 1.
Device summary
Order code
PM6685
PM6685TR
Package
VFQFPN-32 (5mm x 5mm)
VFQFPN-32 (5mm x 5mm)
Packaging
Tube
Tape and Reel
October 2007
Rev 7
1/52
www.st.com
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