PM6686 Datasheet, PDF (1/50 Pages) STMicroelectronics – Constant ON-time control

PM6686
Dual step-down controller with adjustable voltages, adjustable LDO
and auxiliary charge pump controller for notebook
Features
■ 5.5 V to 28 V input voltage range
■ Dual fixed OUT1 = 1.5 V/5 V and OUT2 =
1.05 V / 3.3 V outputs or adjustable OUT1 = 0.7
V to 5.5 V and OUT2 = 0.7 V to 2.5 V outputs,
± 1.5% accuracy over valley regulation
■ Low-side MOSFETs' R_DS(on) current sensing
and programmable current limit
■ Constant ON-time control
■ Frequency selectable
■ Soft-start internally fixed at 2 ms and soft-stop
■ Selectable pulse skipping at light loads
■ Selectable minimum frequency (33 kHz) in
pulse skip mode
■ Independent Power Good and EN signals
■ Latched OVP and UVP
■ Charge pump feedback
■ Fixed 3.3 V/5.0 V, or adjustable output 0.7 V to
4.5 V, ± 1.5% (LDO): 200 mA
■ 3.3 V reference voltage ± 2.0%: 5 mA
■ 2.0 V reference voltage ± 1.0%: 50 µA
Applications
■ Notebook computers
■ Main (3.3 V/5 V), chipset (1.5 V/1.05 V),
DDR1/2/3, graphic cards power supply
■ PDAs, mobile devices, tablet PC or slates
■ 3-4 cells Li+ battery powered devices
VFQFPN-32 5 x 5 mm
Description
PM6686 is a dual step-down controller specifically
designed to provide extremely high efficiency
conversion, with lossless 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. Pulse
skipping technique increases efficiency at very
light load. Moreover a minimum switching
frequency of 33 kHz is selectable to avoid audio
noise issues. The PM6686 provides a selectable
switching frequency, allowing three different
values of switching frequencies for the two
switching sections. The output voltages OUT1
and OUT2 can be programmed to regulate
1.5 V/5 V and 1.05 V/3.3 V outputs respectively or
can deliver two adjustable output voltages. An
optional external charge pump can be monitored.
This device embeds a linear regulator that can
provide 3.3 V/5 V or an adjustable voltage from
0.7 V to 4.5 V output. The linear regulator
provides up to 100 mA output current. LDO can
be bypassed with the switching regulator outputs
or with an external power supply (switchover
function).
Table 1. Device summary
When in switchover, the LDO output can source
up to 200 mA.
Order codes
Package
Packaging
PM6686
PM6686TR
VFQFPN-32L 5 x 5 mm
Tray
Tape and reel
July 2009
Doc ID 15281 Rev 4
1/50
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