l6611 STMicroelectronics, l6611 Datasheet - Page 3

• Manufacturer Part Number: l6611
• Description: Digitally Programmable Secondary Housekeeping Controller
• Manufacturer: STMicroelectronics

PIN DESCRIPTION
DESCRIPTION
The L6611 is a control and housekeeping IC developed in BCD technology; it is intended for acting at the sec-
ondary side of desktop PC's or server's switching power supplies, in presence of standard voltage rails (+3.3V,
+5V, ±12V) generated by a main converter and of a supply line generated by an auxiliary converter. The typical
application circuit is showed on the front page.
The Housekeeping's main function is to control and monitor the voltages generated by both the main and the
auxiliary converter: it senses those voltages, sends feedback signals to the primary controllers for regulation
and, upon detection of an undervoltage (UV), or overvoltage (OV) condition, reports such fault and takes proper
action to protect the system.
However, the peculiar feature of this IC is its digital programming capability that enables an accurate trimming
of the output voltage rails during production test via software, without any use of external discrete trimming com-
ponents or need for manual intervention on the PSU. It is also possible to program some of the monitoring func-
tions and select how UV and OC conditions are handled in the main converter: whether latched-mode (the
information is latched and released only by forcing the restart of the IC) or bouncing-mode (an attempt is made
to automatically restart the converter after 1 second wait).
A key feature of this IC is its contribution to a very low external component count. Besides the extensive use of
onboard programmable switches, which prevents the need for external trimming components, the IC embeds
reference voltages, error amplifiers and most of the housekeeping circuitry normally required.
PIN CONNECTION (top view)
Pin #
1
2
3
MFAULT
Name
Bout
Binv
Main converter on/off control. This pin is a 10mA current sink used for driving an opto-isolator. It
is normally low when PS-ON (#13) is pulled low. If a fault is detected or PS-ON goes high, this
pin goes high too. To allow power up, the functions are digitally blanked out for a period (UVB
function) and MFAULT (#1) stays low. There is no delay for the OV protection function.
Inverting input to the error amplifier for the 3V3 post-regulator (either mag-amp or linear). The
non-inverting input is connected to an internal 1.25V reference that can be digitally trimmed.
Output of the 3V3 error amplifier. It typically drives either a PNP transistor that sets the mag-amp
core or the pass element of a linear regulator. Also node for error amplifier compensation. The
maximum positive level of this output is clamped at about 3.5V to improve response time. Large
signal slew rate is limited to reduce noise sensitivity.
MFAULT
MFAULT
DFAULT
DFAULT
Dmon
Dmon
Bout
Bout
Aout
Aout
Cout
Cout
Cinv
Cinv
Binv
Binv
Ainv
Ainv
Vdd
Vdd
Description
12V
12V
5V
5V
3V3
3V3
-12V
-
-12V
-
PS-ON
PS-ON
PROG
PROG
GND
GND
VREF
VREF
PW-OK
PW-OK
ACsns
ACsns
-
-
L6611
3/28