STMICROELECTRONICS L6611

L6611
DIGITALLY PROGRAMMABLE SECONDARY
HOUSEKEEPING CONTROLLER
■
■
■
■
■
■
■
■
■
■
OV/UV DETECTION FOR 3.3V, +5V, ±12V
RAILS AND 5V (OR 3.3V) AUX. VOLTAGE
AC MAINS UV (BROWNOUT) DETECTION
WITH HYSTERESIS
ON-LINE DIGITAL TRIMMING FOR 5V/12V,
3.3V, 5V (OR 3.3V) AUX. FEEDBACK
REFERENCES AND AC MAINS UV.
DIGITALLY SELECTABLE OPTIONS
ERROR AMPLIFIERS FOR 5V/12V RAILS
(MAIN SUPPLY), 3V3 POST-REGULATOR
(MAG_AMP OR LINEAR) AND AUXILIARY
SUPPLY.
MAIN SUPPLY ON/OFF CONTROL AND
POWER GOOD SIGNAL
50mA CROWBAR DRIVE FOR AUXILIARY
OUTPUT OVP.
OPEN GROUND PROTECTION
8ms DIGITAL SOFT START
64 ms UV/OC BLANKING AT START-UP
BCD TECHNOLOGY
DIP20
SO20
ORDERING NUMBERS:
L6611N
L6611D
L6611DTR(T & Reel)
APPLICATIONS
■ SWITCHING POWER SUPPLIES FOR
DESKTOP PC'S, SERVERS AND WEB
SERVERS
■
SUPERVISOR FOR DISTRIBUTED POWER
TYPICAL APPLICATION CIRCUIT
+12V
+
+5V
WIDE RANGE
MAINS
COM
-12V
+3.3V
MAIN
CONTROL
+5Vaux
AUXILIARY
CONTROL
Bout
VDD
Dmon
Cout
12V
5V
MFault
-12V
Aout
Gnd
3V3
L6611
April 2002
1/28
L6611
Vdd
Vdd
L
U
V
Soft Start
Reset
1.25V(B)
2.50V(B)
2.50V( C)
1.25V( A)
2.50V( A)
+5V +12V
2.50V(B)
ov
uv
ov
OCP Bounce
1.25V (A)
V
r
e
f
2.50V(A)
1.25V (B)
BLOCK DIAGRAM
Binv
Bout
Aout
Ainv
Gnd
Vdd
Cout
Cinv
Prog
Dmon
2/28
Logic and Programmable Trimming
UV
OV
3V3 +5V UV
uv
ov
uv
ov
uv
ov
ov
uv
2.50V( C)
Programming input
Debounce
75ms
10mA
+
_
Disable
+/-12V UV
2.50V( B)
2.50V(B)
Vdd
+3V3
+5V
+12V
50uA
Vdd
+3V3
+5V
+12V
--12V
ACsns
Mfault
PW -OK
/ Data
-
PS -ON
/ Clock
-
Vreg
Dfault
L6611
DESCRIPTION
The L6611 is a control and housekeeping IC developed in BCD technology; it is intended for acting at the secondary 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 components or need for manual intervention on the PSU. It is also possible to program some of the monitoring functions 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)
MFAULT
Binv
Bout
12V
5V
3V3
PROG
GND
--12V
VREF
PS-ON
PW-OK
ACsns
Aout
Ainv
Cout
Cinv
Dmon
DFAULT
Vdd
PIN DESCRIPTION
Pin #
1
2
3
Name
Description
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
MFAULT
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.
Binv
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.
Bout
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.
3/28
L6611
PIN DESCRIPTION (continued)
Pin #
Name
Description
4
Aout
Output of the error amplifier for the main converter. This pin typically drives an optocoupler and is
also used for compensation along with Ainv (pin #5).
5
Ainv
Main loop error amplifier inverting input. The non-inverting input is connected to an internal 2.5V
reference that can be digitally trimmed. A high impedance internal divider from +12V and +5V
UV/OV sense pins (#19, #20) eliminates the need for external divider in most applications. The
pin is used for error amplifier compensation.
6
Cout
Auxiliary loop optocoupler drive. Also node for error amp compensation. Large signal slew rate is
limited to reduce sensitivity to switching noise.
7
Cinv
Inverting input for Auxiliary error amplifier. The non-inverting input is connected to an internal
1.25V reference that can be digitally trimmed.
8
Dmon
Dual or Auxiliary UV/OV monitor, Dmon is programmable to monitor 3V3 or 5V. To allow a correct
power up, the UV function on this pin is blanked out during initial start-up. There is no delay for
the OV function.
9
DFAULT
Dual or Auxiliary fault protection. When Dmon (#8) recognizes an over voltage, DFAULT and
MFAULT (#1) go high. DFAULT is capable of sourcing up to 50mA. Possible applications are a
crowbar across the Auxiliary output or an opto-coupled fault signal to the primary side.
10
Vdd
Positive input supply voltage. Vdd is normally supplied from the Auxiliary power supply output
voltage. If Vdd-UVL detects a sustained under voltage, PW-OK (#12) will be pulled low and
sending MFAULT (#1) high will disable the main converter.
11
ACsns
Analog of bulk voltage for AC fail warning. The usual source of this analog pin is one of the
secondary windings of the main transformer. Hysteresis is provided through a trimmable 50µA
current sink on this pin that is activated as the voltage at the pin falls below the internal reference
(2.5V).
12
PW-OK
/Data
Power good signal for the Main converter. When asserted high, this pin indicates that the
voltages monitored are above their UV limits. There will be typically 250ms delay from the Main
outputs becoming good and PW-OK being asserted. This is nominally an open drain signal. To
improve robustness, this output has a limited current sink capability. In programming mode, this
pin is used for data input; then the absolute maximum rating will be Vdd+0.5V.
13
PS-ON /
Clock
Control pin to enable the Main converter. This pin has debouncing logic. A recognized high value
on this pin will cause PW-OK (#12) to go immediately low and, after a delay of 2.5ms, to shut
down the main PWM by allowing MFAULT (#1) to go high. During normal operation (or if not
used) this pin has to be connected to a voltage lower than 0.8V. In programming mode, this pin
will be used to clock serial data into the chip.
14
VREF
2.5V reference for external applications. This is a buffered pin. Shorting this pin to ground or to
Vdd (#10) will not affect integrity of control or monitor references. An external capacitor (max.
100nF) is required whenever the pin is loaded (up to 5 mA), otherwise it can be left floating.
15
-12V
-12V UV/OV monitor. If connected to a voltage greater than 1.5V (e.g. VREF, #14), the function
will be disabled.
16
GND
Ground pin. The connection integrity of this pin is constantly monitored and in case of either a
bond wire or a PCB trace going open, MFAULT (#1) and DFAULT (#9) will be forced high
switching off the supply.
PROG
The chip has 2 operating modes, depending on PROG input pin biasing:
– normal mode: PROG should be floating or shorted to ground;
– programming mod e: forcing PROG high (+5V), the chip enters programming mode. PW_OK
(#12) and PS_ON (#13) pins are disconnected from their normal functionality and they become
inputs for DATA and CLOCK allowing the chip to be programmed. The programming mode allows selecting some options and adjusting some setpoints;
17
4/28
L6611
PIN DESCRIPTION (continued)
Pin #
Name
Description
18
3V3
19
5V
Input pin for 5V feedback, 5V current sense and 5V UV/OV monitor. 5V UV/OV uses a reference
separate from that used for feedback. This pin connects the 5V part of the Main error amplifier
feedback divider.
20
12V
Input pin for 12V feedback, 12V current sense and 12V UV/OV monitor.12V UV/OV uses a
reference separate from that used for feedback. This pin connects the 12V part of the Main error
amplifier feedback divider.
3V3 UV/OV monitor. It uses a separate reference to the feedback reference.
FUNCTION DESCRIPTION
Name
Description
OVP
Whenever one of the Main output voltages is detected going above its own OVP threshold, this
function set MFAULT (#1) high latching the outputs off. The latch is released after cycling PS-ON
(#13) switch or by reducing Vdd (#10) below the UV threshold.
UVP
Whenever one of the Main output voltages is detected going under its own UVP threshold, this
function sets MFAULT (#1) high; if latch mode has been selected, this function will be latched.
Otherwise an attempt will be made to restart the device after 1 second delay. If ACsns (#11) is
low due to a brownout condition, UVP is disabled.
UVB
Undervoltage blanking. When either converter is enabled, the relevant UV/OC monitoring circuits
must not intervene to allow all outputs to come within tolerance. 64 ms timing is provided; for the
auxiliary converter the timing starts as the IC has a valid supply, for the main converter it starts
as the ACsns pin detects a valid input voltage for the converter.
PW-OK delay
PW-OK delay. After power-up, when the all of the monitored voltages are above their own UV
threshold the PW-OK pin (#12) will be kept low for additional 250ms (typ.) to make sure all the
outputs are settled.
OFF delay
Power-off delay. As soon as PS-ON (#13) pin is recognized high, indicating an imminent turn-off
condition, PW-OK (#12) pin will go low immediately . The converter will be turned off after a
delay of 2.5ms.
Debounce
The PS-ON signal input has debounce logic to prevent improper activation. All of the monitored
inputs have digital filtering/debounce logic on board for high noise immunity.
AC-hysteresis
AC sense hysteresis. Programmable hysteresis is provided on the ACsns input (#11) to avoid
undesired shutdown caused by noise as the voltage at the pin is near the threshold or by the
voltage ripple across the bulk capacitor.
Vdd-OVP
Vdd is monitored for overvoltage. If an overvoltage is detected, MFAULT (#1) and DFAULT (#9)
are latched high.
Vdd-UVL
To prevent false signals of any of IC’s output pins, an under voltage lock-out circuit monitors Vdd
and keeps all IC’s output at their default OFF level until Vdd reaches a sufficient minimum
voltage for ensuring integrity. When Vdd goes below the UV threshold, all latches are reset and
volatile programming memory cleared.
Dual-OVP
Dmon (#8) is monitored to detect an overvoltage condition; in this case MFAULT (#1) and
DFAULT (#9) are latched high.
Dual-UVP
Dmon (#8) is monitored to detect an undervoltage condition; in this case MFAULT (#1) is latched
high and Cout (#6) is pulled low.
5/28
L6611
FUNCTION DESCRIPTION (continued)
Name
Description
Soft-start
The IC provides an on-board 8ms soft-start, a quasi-monotonic ramp from 0V to 2.5V for the A
error amplifier reference voltage, in order to avoid high current peaks in the primary circuit and
output voltage overshoots at start-up. In fact, if this reference gets the nominal value as soon as
the power-up occurs, the A E/A will go out of regulation and tend to sink much more current, thus
forcing PWM to work with the maximum duty-cycle.
Bounce or
Latch-mode
This option allows setting either latched-mode or auto restart after 1 second delay in case of
undervoltage faults.
ABSOLUTE MAXIMUM RATINGS
Symbol
Vdd
Parameter
Value
Unit
-0.5 to +7
V
-0.5 to Vdd+0.5
V
-0.5 to +16
V
Voltage on and -12V UV/OV sense pin
-16 to +5
V
Maximum current in ESD clamp diodes
10
mA
Operating Junction Temperature
-25 to 150
°C
Storage Temperature
-50 to 150
°C
300
°C
Supply voltage
Voltage on PROG, PS-ON/Clock, DFAULT, VREF, and error
amplifier pins
Voltage on MFAULT, PW-OK, Dmon and positive UV, OV, OC, AC
sense pins.
TJ
TSTO
TL
Lead Temperature (soldering, 10 seconds)
THERMAL DATA
Symbol
Rth j-amb
Parameter
Max. Thermal Resistance junction-to-ambient (*)
(*) mounted on board
6/28
DIP20
SO20
Unit
70
120
°C/W
L6611
ELECTRICAL CHARACTERISTCS
(unless otherwise specified: TJ = 0 to 105°C; V DD = 5V, V3V3 = 3.3V, V5V = 5V, V -12V = -12V, ,
VDmon = VDD, PS-ON = low)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
4.2
4.3
4.6
V
3.7
3.8
4.1
V
SUPPLY SECTION
VDD(ON)
Start-up threshold
VDD(OFF) Minimum operating voltage after
turn-on
VDD(H)
Hysteresis
0.25
0.5
0.75
V
VDDOV
Vdd overvoltage
6.1
6.3
6.8
V
IDD-ON
Operating supply current
5
7
mA
No Fault
FAULT THRESHOLDS
Vout = 3.3V
UV
3V3 undervoltage
2.80
2.90
3.00
V
OV
3V3 overvoltage
4.00
4.15
4.30
V
50
65
µA
3V3 bias current
Vout = 12V
UV
12V undervoltage
10.60
10.80
11.00
V
OV
12V overvoltage
13.50
14.00
14.50
V
100
130
µA
12V bias current
Vout = -12V
UV
-12V undervoltage
-9.00
-9.50
-10.0
V
OV
-12V overvoltage
-14.4
-15.0
-15.6
V
VD
-12V disable voltage
1.3
1.5
1.7
V
-65
-50
Voltage to disable comparator
-12V bias current
µA
Vout = 3.3V Aux/Dual (Dmon option)
UV
3V3 undervoltage
2.80
2.90
3.00
V
OV
3V3 overvoltage
4.00
4.15
4.30
V
Vout = 5V Aux/Dual (Dmon option)
UV
5V undervoltage
4.25
4.40
4.55
V
OV
5V overvoltage
6.00
6.25
6.50
V
50
65
µA
5
10
µA
Bias current
ACsense / Hysteresis
Bias current
VACsns = 2.7V
7/28
L6611
ELECTRICAL CHARACTERISTCS (continued)
(unless otherwise specified: TJ = 0 to 105°C; V DD = 5V, V3V3 = 3.3V, V5V = 5V, V -12V = -12V, ,
VDmon = VDD, PS-ON = low)
Symbol
UV
Parameter
Test Condition
AC undervoltage
Trim range
Min.
Typ.
Max.
Unit
2.375
2.50
2.625
V
+5
%
-5
Trim resolution
IACH
HS
0.64
Hysteresis current
20
Hysteresis trim range
-20
Hysteresis adjust step
50
%
80
µA
+20
%
5
%
FAULT OUTPUTS
VPOKH
PW-OK high state
No faults
VPOKL
PW-OK low state
ISINK = 15mA
0.4
V
MFAULT high state leakage
PS-ON = high
1
µA
MFAULT sink current
PS-ON = low, VMFAULT = 4V
6
10
15
mA
MFAULT OV debounce
Minimum OV pulse before
MFAULT is latched.
4
6
8
µs
MFAULT debounce
±12V UV
Minimum UV pulse before
MFAULT is latched.
4
6
8
µs
MFAULT debounce
+5V, 3V3, UV
Minimum UV pulse before
MFAULT is latched.
250
450
650
µs
DFIOH
DFAULT output high source
current
Overvoltage condition
VDFAULT = 1.5V
-25
-50
-95
mA
DFVOH
DFAULT output high voltage
IDFAULT = 0mA, Tamb = 25oC,
Overvoltage condition
2.1
2.4
2.7
V
VOUT
DFAULT output low voltage
IDFAULT = 1mA, no faults
0.3
0.5
0.7
V
DFAULT OV debounce
Minimum OV pulse before
DFAULT is latched.
4
6
8
µs
DFAULT UV debounce
Minimum UV pulse before
DFAULT is latched.
250
450
650
µs
IL
MFISNK
3
V
START-UP / SHUTDOWN FUNCTIONS
t5
DFAULT UV blanking delay
Delay from VDD(on) to DFAULT
UV active.
44
64
84
ms
t1
MFAULT UV blanking delay
Delay from ACSNS high to Main
UV active
44
64
84
ms
t2
PW-OK blanking delay
Main’s UV good to PW-OK high
175
250
325
ms
PS-ON delay time
Delay from PS-ON input to
MFAULT
1.75
2.5
3.25
ms
t4
(tDELAY)
8/28
L6611
ELECTRICAL CHARACTERISTCS (continued)
(unless otherwise specified: TJ = 0 to 105°C; V DD = 5V, V3V3 = 3.3V, V5V = 5V, V -12V = -12V, ,
VDmon = VDD, PS-ON = low)
Symbol
Parameter
VIH
PS-ON Input High Voltage
VIL
PS-ON Input Low Voltage
Test Condition
IIN = -200µA
Min.
Typ.
Max.
2.0
Unit
V
0.8
PS-ON Input high clamp
IPS-ON = 100 µA
PS-ON Pull-up to VDD
VPS-ON = 0V
25
50
100
KΩ
t3
PS-ON debounce
PS-ON input minimum pulse
width for a valid logic change.
50
75
100
ms
tSS
Error Amp. A Soft-Start period
VFB quasi-monothonic ramp from
0 to 2.5V
8
ms
Soft Start Step
Ramp 0V to 2.5V
39
mV
RPS-ON
VSTEP
Vdd
+0.7
V
V
VOLTAGE REFERENCE (BUFFERED EXTERNAL PIN)
VREF
ISC
Output Voltage
IREF = 1 - 5 mA; CREF = 47nF
Short circuit current
VREF = 0
2.375
2.50
2.625
V
10
20
mA
2.50
2.625
V
+5
%
MAIN CONVERTER FEEDBACK (ERROR AMPLIFIER A)
VFB
Input Voltage
T j = 25° C
Trim Range
About nominal
2.375
-5
Trim resolution
ZFB
Divider impedance
0.64
from Ainv to GND. 5V and 12V
connected to GND.
35
Temperature coefficient
W5
50
%
65
Ω/°C
26
Divider 5/12 weighting
5V contribution to 5/12 feedback
47
AVOL
Voltage gain
2V<VOUT<4V
65
GBW
Unity gain bandwidth
PSRR
Power supply rejection ratio
4.5V<VDD<6V
IOUTL
Output sink current
VFB = 2.7V, VOUT = 1.1V
IOUTH
Output source current
VFB = 2.3V, VOUT = 4V
VOUTH
Output high level
VFB = 2.3V, ISOURCE = 1 mA
VOUTL
Output low level
VFB = 2.7V, ISINK = 2 mA
50
kΩ
53
%
dB
3
MHz
60
70
dB
2
5
8
mA
-1.0
-1.5
-2.0
mA
4
4.5
V
0.7
1.1
V
1.25
1.28
V
+5
%
MAGAMP OR LINEAR POST-REGULATOR FEEDBACK (ERROR AMPLIFIER B)
VFB
Input Voltage
T j = 25° C
Trim Range
About nominal
1.22
-5
9/28
L6611
ELECTRICAL CHARACTERISTCS (continued)
(unless otherwise specified: TJ = 0 to 105°C; V DD = 5V, V3V3 = 3.3V, V5V = 5V, V -12V = -12V, ,
VDmon = VDD, PS-ON = low)
Symbol
Parameter
Test Condition
Min.
Typ.
Trim resolution
0.64
IBIAS
Input bias current
-0.1
AVOL
Voltage gain
GBW
Unity gain bandwidth
PSRR
Power supply rejection ratio
4.5V<VDD<6V
IOUTL
Output sink current
VFB = 1.4V, VOUT = 1.1V
IOUTH
Output source current
VFB = 1.1V, VOUT = 3V
VOUTH
Output high level
VFB = 1.1V, ISOURCE = 1 mA
VOUTL
Output low level
VFB = 1.4V, ISINK = 2 mA
2V<VOUT<4V
Max.
Unit
%
-1
65
µA
dB
3
MHz
60
70
dB
2
5
8
mA
-1.0
-1.5
-2.0
mA
3
3.6
4
V
0.7
1.1
V
1.25
1.28
V
+5
%
AUXILIARY CONVERTER FEEDBACK (ERROR AMPLIFIER C)
VFB
Input Voltage
Tamb = 25° C
Trim Range
About nominal
1.22
-5
Trim resolution
0.64
IBIAS
Input bias current
-0.1
AVOL
Voltage gain
GBW
Unity gain bandwidth
PSRR
Power supply rejection ratio
4.5V<VDD<6V
IOUTL
Output sink current
VFB = 1.4V, VOUT = 1.1V
IOUTH
Output source current
VFB = 1.1V, VOUT = 4V
VOUTH
Output high level
VFB = 1.1V, ISOURCE = 1 mA
VOUTL
Output low level
VFB = 1.4V, ISINK = 2 mA
VOUTL
Output low level
Dmon = 2.7V, ISINK = 5 mA
2V<VOUT<4V
%
-1
65
µA
dB
3
MHz
60
70
dB
2
5
8
mA
-1.0
-1.5
-2.0
mA
4
4.5
0.7
V
1.1
V
0.25
V
1.5
V
PROGRAMMING FUNCTIONS
VPROGLO Prog Input Low
VPROGHI Prog Input High
RPROG
3.5
Prog Pull Down
100
VCLOCKLO Clock Input Low
VCLOCKHI Clock Input High
10/28
V
KΩ
0.8
2
V
V
L6611
ELECTRICAL CHARACTERISTCS (continued)
(unless otherwise specified: TJ = 0 to 105°C; V DD = 5V, V3V3 = 3.3V, V5V = 5V, V -12V = -12V, ,
VDmon = VDD, PS-ON = low)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
FCLOCK
Clock Frequency
0.8
MHz
VDATALO
Data Input Low
1.5
V
VDATAHI
Data Input High
2
V
IFUSE
PROM Fuse Current
400
mA
tFUSE
PROM Fusing Time
3
ms
11/28
L6611
TYPICAL ELECTRICAL CHARACTERISTICS
Figure 1. Supply start-up, UV and OV
Figure 4. Monitored inputs bias current
VDD [V]
6.5
80
over voltage
IB [µA]
70
5Voutput
5.5
60
50
start-up
4.5
12Voutput
3.3Voutput
UV
40
3.5
30
-50
-25
0
25
50
75
100 125 150
-50
-25
0
25
Figure 2. IC Supply current vs. supply voltage
75
100 125 150
Figure 5. 3.3V fault thresholds
IDD [mA]
5
10
V3.3V [V]
Dmon = VDD
Tj = 25 °C
8
50
T [OC]
T [OC]
overvoltage
4
6
4
3
undervoltage
2
0
2
0
2
4
6
8
-50
10
-25
0
Figure 3. IC Supply current
7
25
50
75
100
125 150
T [OC]
VDD [V]
Figure 6. 5V fault thresholds
IDD [mA]
7
6
V5V [V]
6
overvoltage
5
5
4
4
undervoltage
3
3
-50 -25
0
25
50
T [ OC]
12/28
75 100 125 150
-50
-25
0
25
50
T [OC]
75
100 125 150
L6611
TYPICAL ELECTRICAL CHARACTERISTICS (continued)
Figure 7. 12V fault thresholds
15
Figure 10. -12V fault thresholds
V+12V [V]
-6
overvoltage
14
-9
overvoltage
13
-12
12
undervoltage
undervoltage
-15
11
10
-50
-25
0
25
50
T
75
100 125 150
Figure 8. 3.3V/5V Dmon fault thresholds
0
-18
-50 -25
[OC]
0
25
50
75 100 125 150
Figure 11. ACsense and external voltage
references
VDMON [V]
2.7
[V]
+5V overvoltage
-3
-6
2.6
+5V undervoltage
-9
+3.3V overvoltage
2.5
+3.3V undervoltage
2.4
-12
-15
-18
2.3
-50
-25
0
25
50
75
100 125 150
-50 -25
T [OC]
0
25
50
75 100 125 150
T [OC]
Figure 9. -12V bias current
Figure 12. Error amplifier A, B and C reference
voltage
-20
3
[V]
2.5
-30
A
2
-40
1.5
B-C
1
-50
-50
-25
0
25
50
75
100 125 150
0.5
-50
-25
0
25
50
75
100 125 150
T [ OC]
13/28
L6611
TYPICAL ELECTRICAL CHARACTERISTICS (continued)
Figure 13. Error amplifiers (A, B, C) Gain and Phase
200
0o
150
phase
100
90 o
50
gain
f
mφ
0
180 o
-50
-100
-150
-200
1e+00
14/28
1e+01
1e+02
1e+03
1e+04
1e+05
1e+06
1e+07 7e+07
L6611
APPLICATION INFORMATION INDEX
1 On board digital trimming and mode selection..................................................................................Page 16
2 Error amplifiers and reference voltages ..................................................................................................... 18
Main section: error amplifier A and Soft -Start
E/A and reference voltage
3.3V section: error amplifier B
Auxiliary section: error amplifier C
3 Normal operation timing diagram ............................................................................................................... 20
4 Undervoltage, overvoltage and relevant timings ........................................................................................ 21
5 AC sense (mains undervoltage warning) ................................................................................................... 22
6 Application example ................................................................................................................................... 23
7 Application ideas ........................................................................................................................................ 25
15/28
L6611
APPLICATION INFORMATION
1
ONBOARD DIGITAL TRIMMING AND MODE SELECTION
By forcing the PROG input pin high, the chip enters programming mode: the multifunction pins PW_OK and
PS_ON are then disconnected from their normal functions (output pins) and are connected to internal logic as
DATA and CLOCK inputs respectively, allowing chip programming even when the device is assembled on the
application board. Onboard chip programming allows:
– selecting some working options;
– reference voltage setpoints adjusting.
It is also possible to verify the expected results before programming the chip definitively, in first instance, data
can be loaded into a re-writeble volatile memory (a flip-flop array) where they are kept as long as the chip is
supplied and can be changed as many times as one desires. A further operation is necessary to confirm the
loaded data and permanently store them into a PROM (a poly-fuse array) inside the IC.
Several steps compose the trimming/programming process:
1. PROG pin is forced high;
2. a clock signal is sent to the PS-ON/clock pin;
3. a byte with the following structure:
MSB
LSB
D3
D2
D1
D0
A3
A2
Data
A1
A0
Address
is serially sent to the PW-OK/DATA pin and loaded into the IC's volatile memory bit by bit on the falling edges
of the clock signal (see Fig. 14); "Address" is the identification code of the parameter that has to be trimmed
and "Data" contains the tuning bits;
4. PROG pin is forced low (warning: Vdd must never fall below VddUVL0 during this process otherwise the contents of the volatile memory will be lost) and the result of the previous step is checked;
5. after any iterations of the steps 1-4 that might be necessary to achieve the desired value, force PROG pin
high and send the following burn code
MSB
LSB
0
0
0
0
1
1
1
1
to permanently store the data in the PROM memory.
Table 1 shows the list of the 6 programmable classes of functions, each one identified by a different code
A0..A3, and the corresponding trimmable parameter(s); in table 2 it is possible to find the trim coding for the E/
A reference setpoints and in table 3 all the selections mode option coding are showed. The timing diagram of
fig. 14 shows the details of data acquisition.
Table 1. Programmable functions
Address
Parameter(s)
Default value
Tuning bits
0001
Error amplifier A threshold
2.50V
D3
D2
D1
DO
0010
Error amplifier B threshold
1.25V
D3
D2
D1
DO
0011
Error amplifier C threshold
1.25V
D3
D2
D1
DO
0100
AC sense threshold
2.50V
D3
D2
D1
DO
AC sense hysteresis
50µA
D2
D1
DO
0101
0110
Latch/Bounce mode selection
Latch mode
D3
Enable/Disable 12V UV/OV function
Enabled
D3
Enable/Disable 5V UV/OV function
Enabled
5V/3V3 Dmon selection
5V selection
D2
D1
don’t care
16/28
L6611
Table 2. Trim Coding
Parameter
E/A A threshold
2.5V typ.
E/A B threshold
1.25V typ.
E/A C threshold
1.25V typ.
ACsns threshold
2.5V typ.
ACsns
Hysteresys
50µA typ.
Address
0001
0010
0011
0010
0101
Tuning Bits
D3 D2 D1 D0
D3 D2 D1 D0
∆V [mV]
D3 D2 D1 D0
∆V [mV]
D3 D2 D1 D0
∆V [mV]
D3 D2 D1 D0
∆V [mV]
D2 D1 D0
∆I [µA]
0111
+112
+56
+56
+112
0110
+96
+48
+48
+96
0101
+80
+40
+40
+80
0100
+64
+32
+32
+64
0011
+48
+24
+24
+48
+7.5
0010
+32
+16
+16
+32
+5.0
0001
+16
+8
+8
+16
+2.5
0000
0
0
0
0
0
1111
-16
-8
-8
-16
-2.5
1110
-32
-16
-16
-32
-5.0
1101
-48
-24
-24
-48
-7.5
1100
-64
-32
-32
-64
-10
1011
-80
-40
-40
-80
1010
-96
-48
-48
-96
1001
-112
-56
-56
-112
1000
-128
-64
-64
-128
Table 3. Mode coding
Parameter
Bounce or Latch
Mode
Address
A3 A2 A1 A0
0101
Enable/Disable
12V UV/OV
Enable/Disable
5V UV/OV
5V/ 3.3V Dmon
Selection
A3 A2 A1 A0
0110
Tuning Bit
Bit Value
D3
D3
D2
D1
0
Latch
Enabled
Enabled
5V
1
Bounce
Disabled
Disabled
3.3V
Figure 14. Trimming/programming procedure: timing diagram
MSB
0
LSB
1
0
1
0
0
0
1
PROG
PS_ON/Clock
PW_OK/Data
17/28
L6611
2
ERROR AMPLIFIERS AND REFERENCE VOLTAGES
Three error amplifiers are implemented on the IC to achieve regulation of the output voltages: a brief description
follows for each section.
– Main section: error amplifier A and Soft-Start.
The circuit is designed to directly control the Main primary PWM through an optocoupler, providing
very good regulation and galvanic isolation from the primary side. Typical solutions require a shunt
regulator, like the TL431, as a reference and feedback amplifier to sense the output voltage and generate a corresponding error voltage; this voltage is then converted in a current transferred to the primary side through the optocoupler.
The feedback E/A amplifier is integrated in the IC: its non-inverting input is connected to an internally generated voltage reference, whose default value is typically 2.5V. It can however be trimmed to obtain a better
precision (see "On board trimming and mode operating" section). Then, no TL431 is needed.
The E/A inverting input (Ainv, pin#5) and the E/A output (Aout, pin#4) are externally available and the
frequency compensation network (Zc) will be connected between them (see fig. 15).
The high impedance (in the hundred kΩ) internal divider from 12V and 5V UV/OV sense pins eliminates the need for an external one in most applications, allowing a further reduction in the number of
external component.
Under closed loop condition, the two upper branches, connected to 12V and 5V pins, supply equally
the current flowing through R3= 80.6K (equal to 2.5V/R3).
In order to avoid high current peaks in the primary circuit and output voltage overshoots at start-up,
the IC provides an on-board 8ms soft-start, a quasi-monotonic ramp from 0V to 2.5V for the A error
amplifier reference voltage,. In fact, if this reference gets the nominal value as soon as the power-up
occurs, the A E/A will go out of regulation and tend to sink much more current, thus forcing PWM to
work with the maximum duty-cycle.
– E/A and references voltage
Being the inverting input of E/A externally available, it is possible to change the "weight" of the two
contributions or even eliminate one of them by connecting external resistors of much lower value (RL,
RH1 and/or RH2 in fig. 15) that bypass the internal ones appropriately.
For example using RL=2.4K, R H1=3.9K and RH2=24K, then the ratio between +5V and +12V output
weight will be equal to 6:4.
By simply making RH1 = RL (for example 2.4K) with no RH2, only the +5V output is kept under feedback because the contribution of +12V branch (through the internal 600K resistor) will be negligible.
The pin #24 (12V) has to be connected to +12V output to guarantee the OV/UV monitoring.
Figure 15. Main feedback section
VDD
to MAIN
control
+12V output
+5V output
RB
5V
12V
optional, to change
feedback weight
RH1
168K
Aout
RH2
600K
Ainv
_
+
80.6K
RL
8ms SS
L6611
+2.5V
GND
Zc
– 3.3V section, error amplifier B.
It is the error amplifier used to set the magamp core through an external circuitry (see a typical schematic in figure 16).
The non-inverting input of the error amplifier is connected to a trimmable 1.25V internal voltage reference (see "On board trimming and mode operating" paragraph). The E/A inverting input is externally available (Binv, pin#2) and is connected to the output divider (RH and R L); the output pin (Bout,
18/28
L6611
pin#3) drives the external circuitry that biases the magamp core. Between these pins it is connected
the compensation network (ZC). The maximum positive output voltage is clamped at about 3.5V to
improve response time.
The feedback control circuit determines the magamp "off" time, converting the voltage at the output
of error amplifier into a current IR, which resets the magamp. If the output voltage exceeds its preset
value, V(Bout) decreases; this causes a higher voltage across RC which, in turn, implies a larger voltage across R E and a larger reset current IR (VBE of Q1 is supposed constant). A larger IR causes the
PWM waveform across D2 to get narrower. This pulls the output voltage back to the desired level and
achieves regulation.
It is possible to use this section to drive a pass transistor to obtain 3.3V with a linear regulator; in the
"Application idea" section an example is showed to implement this solution.
Figure 16. Magamp control feedback section
+3.3V
magamp
L
C
VD2
D2
RH
D1
Zc
RE
IR
Q1
RC
Binv
_
Bout
+
RS
RL
+1.25V
L6611
– Auxiliary section, error amplifier C.
This section (fig. 17) provides the feedback signal for the auxiliary converter following the same operating principles as the Main section. The auxiliary output voltage (Vaux) is often defined as "Standby
voltage" because the converter remains alive during standby condition (the Main converter is stopped)
to supply the chip and all the ancillary circuits. Typical values for its output voltage are 5V or 3.3V.
The inverting input (Cinv, pin#7) is connected to the output voltage through an external resistor divider
whereas the non-inverting one is connected to a 1.25V trimmable internal voltage reference (see "On
board trimming and mode operating" paragraph).
The compensation network Zc(aux) is placed between E/A inverting input and output pins.
When Dmon recognizes an undervoltage condition on the auxiliary output, an internal n-channel MOS
(in open drain configuration) grounds E/A output pin; the high current flowing through the optocoupler
is then transferred to the primary side causing a duty cycle as short as possible; this prevents a high
energy transfer from primary to secondary under short circuit conditions, thus reducing the thermal
stress on the power components.
Figure 17. Auxiliary feedback section
VAUX
to AUX
control
RH
RB
RL
Zc(aux)
Cinv
DMON
_
+
Cout
OCP bounce
GND
+1.25V
L6611
19/28
L6611
3
NORMAL OPERATION TIMING DIAGRAM (FIG. 18)
The time intervals t1-t5 are listed below
– t1: UV/OC blanking of MFAULT. While Main outputs are ramping up, the UV comparators are blanked
for this interval to prevent a false turn-off. No such blanking is applied to OV faults.
– t2: PW-OK delay. This period starts when all monitored outputs and AC sense are above their respective UV levels and finishes at PW-OK going high.
– t3: PS-ON debounce period. The voltage on PS-ON must be continuously present in a high or low state
for a minimum period for that state to be recognized.
– t4: Tdelay. The time from PS-ON being recognized as going high to MFAULT going high. This is to
provide a power down warning. When PS-ON requests power off, PW-OK goes low immediately.
– t5: UV blanking of DFAULT. During initial power up a period of UV blanking is applied to DFAULT as
soon as Vdd to the chip is in the correct range. No such blanking is applied to OV faults.
Figure 18. Normal Operation Timing Diagram (ON/OFF with PS-ON or the AC power switch).
On
AC
Off
Vdd(on)
Vdd(on)
Vdd
Vdd-ok
t5
UVBdfault
ACsns
ACsns_high
ACsns_low
Off
PS-ON
On
t3
t3
Mfault
Main
OPs
t2
t4
t2
POK
UVBmfault
t1
20/28
t1
L6611
4
UNDERVOLTAGE, OVERVOLTAGE, DETECTION AND RELEVANT TIMINGS
The IC provides on-board undervoltage and overvoltage protection for 3V3, ±5V, ±12V Main input pins and
Dmon auxiliary input pin. Overcurrent protection is available for 12V and 5V or 3.3V, digitally selectable. The
internal fault logic is illustrated in figure 19.
Figure 19. Simplified Fault logic
Debounce 6µs
Main_OV
In
Clock
Debounce 6µs
+/-12V_Main_UV
In
Clock
Out
Reset
Reset
Out
Reset
Mfault
Reset
S
Debounce 500µs
+3V3 +5V_Main_UV
In
Clock
Reset
ACsense
Q
Latch
Vdd
Out
Reset
R
UVB 64ms
In
Clock
Out
Reset
+
Vref
Vdd
Dmon_OV
Debounce 6µs
In
Clock
S
Out
Reset
Q
Dfault
Latch
Reset
Reset
Debounce 500µs
Dmon_UV
In
Clock
Out
Reset
Vdd
Reset
UVB 64ms
Vdd_OV
In
Clock
Vdd_UVL
Out
Reset
Cout
D_UVB
S
Reset
Reset
Q
Latch
Reset
R
Delay 1s
Restart Mode
In
Clock
Out
Reset
Reset
Delay 2.5ms
In
Clock
S
Q
Out
Reset
Vdd
Reset
PW-OK
Latch
Vdd
PS-ON
R
R
Debounce 75ms
In
Clock
Out
Reset
Vdd
Delay 250ms
In
Clock
Out
Reset
ON
– Main inputs overvoltage: whenever one of main outputs (3.3V, +5V, ±12V) is detected as going overvoltage, MFAULT is latched high (which stops the Main PWM) and PW-OK goes low. Cycling the PSON switch or reducing Vdd below its undervoltage threshold releases the latch. A delay of 6µs is implemented before MFAULT latching.
The OV protection for the 12V and 5V outputs can be disabled (see "On board trimming and mode operating" section).
– Main inputs undervoltage: when an undervoltage on main outputs is detected, MFAULT is latched
high (the Main PWM stops) and PW-OK goes low. The latches are released, by default, cycling the PSON switch or reducing Vdd below its undervoltage threshold (latching mode); optionally, an attempt is
made to restart the supply after of 1 second (bounce mode). The choice depends on the selected mode
(see "On board trimming and mode operating" section).
Debounce logic is implemented for 3.3V and 5V so that an undervoltage condition on these signals has
to last 450µs to be recognized as valid while 6µs debounce logic is implemented for 12V and -12V input
signal. When all main undervoltages are over and ACsns is OK (see the relevant section), PW_OK goes
high after a delay of 250ms.
– Dmon input overvoltage: whenever the Dmon input pin is detected as going overvoltage, both
MFAULT and DFAULT are latched high. The latch is released by reducing Vdd below its undervoltage
threshold. Debounce logic is implemented so that MFAULT and DFAULT signals are latched only if the
overvoltage condition lasts more than 6µs.
To protect the load against overvoltage, typical solutions make use of a power crowbar (SCR) driven by
21/28
L6611
DFAULT; in the "Application ideas" section, another simple circuit is showed to guarantee the same protection without the SCR.
– Dmon input undervoltage: when an undervoltage on Dmon is detected, MFAULT is put high, Cout is
pulled low (an internal OCP_BOUNCE signal is generated, see fig. 19) and PW_OK falls down. This
function is enabled 64ms after the UVLO signal falls down. Debounce logic is implemented so that
MFAULT and OCP_BOUNCE signals are generated only if the undervoltage condition lasts more than
500µs.
The Dmon UV and OV protections can be set to work with thresholds set for 5V or 3.3V output voltage:
the choice depends on the IC programming.
Figure 20. Fault timing diagram
Output
Output
Mfault
Mfault
POK
POK
Main output’s overvoltage
Main output’s undervoltage
Dmon(*)
Dmon(*)
Dfault current
Cout
Mfault
Mfault
POK
POK
Auxiliary output’s overvoltage
Auxiliary output’s undervoltage
(*) Dmon is connected to the Auxiliary output Rail
5
AC SENSE (MAINS UNDERVOLTAGE WARNING)
The device monitors the primary bulk voltage and warns the system when the power is about to be lost pulling
down the PW_OK output.
The ACsns pin is typically connected to one of the windings of the main transformer (see fig. 21). Through a
single-diode rectification filter, a voltage equal to VB = VBULK/N (where VBULK is the voltage across the bulk capacitor on primary side and N is the transformer turn ratio) is present at point B. A resistor (RF) could be useful
to clamp voltage spikes present.
The fault signal is generated by means of AC_GOOD, the output of an internal comparator; this comparator is
internally referred to a trimmable 2.5V reference and indicates an AC fault if the voltage applied at its externally
available (non-inverting) input is below the internal reference, as shown in fig. 21.
This comparator is provided with current hysteresis instead of a more usual voltage hysteresis: an internal 50µA
current generator is ON if the voltage is below 2.5V and is turned off when the voltage applied at the non-inverting input exceeds 2.5V.
This approach provides an additional degree of freedom: it is possible to set the ON threshold and the OFF
22/28
L6611
threshold separately by properly choosing the resistors of the external divider. The following relationships can
be established for the ON (VB (ON)) and OFF (VB (OFF)) thresholds of the input voltage:
VB ( O N ) – 2.5
2.5
---------------------------------- = -------- + 50 µA
R1
R2
R2
VB ( O FF ) ⋅ -------------------- = 2.5
R1 + R 2
which, solved for R1 and R2, yields:
VB ( O N ) – VB ( O FF )
R 1 = ------------------------------------------------50µ A
2.5
R 2 = R 1 ⋅ ------------------------------------VB ( O FF ) – 2.5
Both the ACsns threshold and the hysteresis current can be trimmed (see "On board trimming and mode operating" section).
Figure 21. ACsns circuit and timing diagram
RF
L6611
+2.5V
VB
B
AC_GOOD
_
+
VB(on)
R1
ACsns
R2
IHYS=50µA
GND
6
C1
VB(off)
AC_GOOD
VACsns
∆
∆=50µA*R1
∆
PW_OK
ON
APPLICATION EXAMPLE
In applications like desktop PC's, server or web server, the system usually consists of two converters (Main and
Auxiliary) that can be supplied directly from either the AC Mains or a PFC stage. The control and supervision at
the secondary side is usually entrusted to a housekeeping circuit.
The Auxiliary section supplies a stand-by voltage (5V typ.) through a flyback converter. The Main section, in
forward configuration, presents 4 standard outputs (3.3V, +5V, ±12V).
At the secondary side, the housekeeping circuitry governed by the L6611 checks the outputs and sends control
signals to the primary side through three optocouplers. It also generates power good information to the system
while managing all timings during power-up and power-down sequences. In fig. 22 a detailed circuit for the secondary side is presented; it is possible to note the very low number of external components required.
Simply connecting the power supply outputs to the L6611 relevant pins ensures the protection against over/undervoltage in the Main section.
A crowbar on the auxiliary output is switched on through DFAULT in case of overvoltage.
The L6611 is supplied by the Auxiliary output; the signals sent to the primary side are:
– a "digital" ON/OFF signal through an optocoupler that drives the relevant pin of primary Main controller
to switch the Main converter ON and OFF;
– two analog signals that provide voltage feedback for both the Auxiliary and the Main section, driving the
primary controller pins responsible for the duty cycle modulation.
23/28
L6611
Figure 22. Detailed Secondary Side
PRIMARY SIDE CONTROL & POWER MANAGEMENT
24/28
+12V
+5V
COM
-12V
+3.3V
L6611
M-FAULT
Binv
Bout
Aout
Ainv
Cout
Cinv
DMON
DFAULT
Vdd
12V
5V
3V3
PROG
GND
-12
VREF
PS-ON
PW-OK
ACsns
+5Vaux
L6611
7
APPLICATION IDEAS
In fig. 23 a circuit is suggested to obtain the regulated +3.3V output with a linear configuration instead of the
Magamp circuitry.
In this case the output of the E/A modulates the gate-source voltage of a power MOS in series with the power
stage.
In fig. 24 a simple and cheap latch circuit is showed to manage an OV fault on the Auxiliary output in the same
way of an OC (UV) fault, without having recourse to a (expensive) power crowbar. By tuning the value of RSET
it is possible to set the voltage value that triggers the latch circuit; C DEL defines the turn-on delay. A diode connected between the collector of Q1 and Cout pulls down the output of the auxiliary E/A: this has the same effect
of the OCP_bounce internal signal that guarantees the reduction of duty cycle.
Figure 23. Controlling a Linear Regulator with the Error Amplifier B
+5V
+3.3V
L
C2
C1
RH
ZC
+12V
_
Binv
RB
+
Bout
RL
+1.25V
L6611
Figure 24. Auxiliary OVP without Crowbar
100
DMON
Cout
VAUX
D1
BAT42
5K6
RSET
Q2
BC558
L6611
Q1
BC548
CDEL
5K6
25/28
L6611
mm
DIM.
MIN.
a1
0.254
B
1.39
TYP.
inch
MAX.
MIN.
TYP.
MAX.
0.010
1.65
0.055
0.065
b
0.45
0.018
b1
0.25
0.010
D
25.4
1.000
E
8.5
0.335
e
2.54
0.100
e3
22.86
0.900
F
7.1
0.280
I
3.93
0.155
L
OUTLINE AND
MECHANICAL DATA
3.3
0.130
DIP20
Z
26/28
1.34
0.053
L6611
mm
inch
OUTLINE AND
MECHANICAL DATA
DIM.
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
2.35
2.65
0.093
0.104
A1
0.1
0.3
0.004
0.012
B
0.33
0.51
0.013
0.020
C
0.23
0.32
0.009
0.013
D
12.6
13
0.496
0.512
E
7.4
7.6
0.291
0.299
e
1.27
0.050
H
10
10.65
0.394
0.419
h
0.25
0.75
0.010
0.030
L
0.4
1.27
0.016
0.050
SO20
K
0˚ (min.)8˚ (max.)
L
h x 45˚
A
B
e
A1
K
C
H
D
20
11
E
1
0
1
SO20MEC
27/28
L6611
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
The ST logo is a registered trademark of STMicroelectronics
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