STMICROELECTRONICS VIPER26HD

VIPER26
Fixed frequency VIPerTM plus family
Features
■
800 V avalanche rugged power section
■
PWM operation with frequency jittering for low
EMI
■
Operating frequency:
– 60 kHz for L type
– 115 kHz for H type
SO16 narrow
SO-16
DIP-7
Description
■
Standby power < 50 mW at 265 VAC
■
Limiting current with adjustable set point
■
On-board soft-start
■
Safe auto-restart after a fault condition
■
Hysteretic thermal shutdown
The device is an off-line converter with an 800 V
avalanche ruggedness power section, a PWM
controller, user defined overcurrent limit,
protection against feedback network
disconnection, hysteretic thermal protection, soft
start up and safe auto restart after any fault
condition.
Advance frequency jittering reduces EMI filter
cost. Burst mode operation and the devices very
low consumption both help to meet the standard
set by energy saving regulations.
Application
■
Auxiliary power supply for appliances
■
Power metering
■
LED drivers
■
SMPS for set-top boxes, DVD players and
recorders
Figure 1.
Typical topology (VOUT ≤VDDCSon)
DC Output Voltage
DC Input Voltage
-
DRAIN
COMP
VIPER26
GND
Table 1.
VDD
LIM
FB
Device summary
Order codes
Package
Packaging
DIP-7
Tube
VIPER26LN
VIPER26HN
VIPER26HD
Tube
VIPER26HDTR
Tape and reel
SO16 narrow
VIPER26LD
Tube
VIPER26LDTR
Tape and reel
September 2010
Doc ID 17736 Rev 2
1/25
www.st.com
25
Contents
VIPER26
Contents
1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Typical power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3
Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.3
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5
Typical electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6
Typical circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7
Power section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8
High voltage current generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9
Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10
Soft start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11
Adjustable current limit set point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
12
FB pin and COMP pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
13
Burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
14
Automatic auto restart after overload or short-circuit . . . . . . . . . . . . . 17
15
Open loop failure protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
16
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
17
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2/25
Doc ID 17736 Rev 2
VIPER26
1
Block diagram
Block diagram
Figure 2.
2
Block diagram
Typical power
Table 2.
Typical power
230 VAC
Part number
VIPER26
85-265 VAC
Adapter(1)
Open frame(2)
Adapter(1)
Open frame(2)
18 W
20 W
10 W
12 W
1. Typical continuous power in non ventilated enclosed adapter measured at 50 ° C ambient.
2. Maximum practical continuous power in an open frame design at 50 ° C ambient, with adequate heat
sinking.
Doc ID 17736 Rev 2
3/25
Pin settings
3
VIPER26
Pin settings
Figure 3.
Connection diagram (top view)
.#
.!
!-V
Note:
The copper area for heat dissipation has to be designed under the DRAIN pins.
Table 3.
Pin description
Pin n.
Name
Function
DIP-7 SO16
1
1-2
GND
Connected to the source of the internal power MOSFET and controller
ground reference.
-
4
N.A.
Not available for user. It can be connected to GND (pins 1-2) or left not
connected.
2
5
VDD
Supply voltage of the control section. This pin provides the charging current
of the external capacitor.
3
6
LIM
This pin allows setting the drain current limitation. The limit can be reduced
by connecting an external resistor between this pin and GND. Pin left open if
default drain current limitation is used.
FB
Inverting input of the internal trans conductance error amplifier. Connecting
the converter output to this pin through a single resistor results in an output
voltage equal to the error amplifier reference voltage (See VFB_REF on
Table 7). An external resistors divider is required for higher output voltages.
4
5
7,8
4/25
7
8
Output of the internal trans conductance error amplifier. The compensation
network have to be placed between this pin and GND to achieve stability and
good dynamic performance of the voltage control loop. The pin is used also
COMP
to directly control the PWM with an
optocoupler. The linear voltage range extends from VCOMPL to VCOMPH
(Table 7).
High voltage drain pin. The built-in high voltage switched start-up bias
13-16 DRAIN current is drawn from this pin too.
Pins connected to the metal frame to facilitate heat dissipation.
Doc ID 17736 Rev 2
VIPER26
Electrical data
4
Electrical data
4.1
Maximum ratings
Table 4.
Symbol
Value
Pin
(DIP-7)
Parameter
Unit
Min
VDRAIN
7, 8
Drain-to-source (ground) voltage
EAV
7, 8
IAR
Max
800
V
Repetitive avalanche energy (limited by TJ = 150 °C)
5
mJ
7, 8
Repetitive avalanche current (limited by TJ = 150 °C)
1.5
A
IDRAIN
7, 8
Pulse drain current (limited by TJ = 150 °C)
3
A
VCOMP
5
Input pin voltage
-0.3
3.5
V
VFB
4
Input pin voltage
-0.3
4.8
V
VLIM
3
Input pin voltage
-0.3
2.4
V
VDD
2
Supply voltage
-0.3
Self
limited
V
IDD
2
Input current
20
mA
Power dissipation at TA < 40 °C (DIP-7)
1
W
1.5
W
PTOT
TJ
TSTG
4.2
Absolute maximum ratings
Power dissipation at TA < 60 °C (SO16N)
Operating junction temperature range
-40
150
°C
Storage temperature
-55
150
°C
Thermal data
Table 5.
Thermal data
Max value
Symbol
Parameter
Unit
SO16N
DIP-7
RthJP
Thermal resistance junction pin
(Dissipated power = 1 W)
25
35
° C/W
RthJA
Thermal resistance junction ambient
(Dissipated power = 1 W)
60
100
° C/W
RthJA
Thermal resistance junction ambient (1)
(Dissipated power = 1 W)
50
80
° C/W
1. When mounted on a standard single side FR4 board with 100 mm2 (0.155 sq in) of Cu (35 µm thick)
Doc ID 17736 Rev 2
5/25
Electrical data
4.3
VIPER26
Electrical characteristics
(TJ = -25 to 125 °C, VDD = 14 V (a); unless otherwise specified)
Table 6.
Symbol
VBVDSS
IOFF
RDS(on)
COSS
Table 7.
Symbol
Power section
Parameter
Test condition
Min
Typ
Max
Unit
Break-down voltage
IDRAIN = 1 mA,
VCOMP = GND, TJ = 25 °C
OFF state drain current
VDRAIN = max rating,
VCOMP = GND
60
µA
IDRAIN = 0.2 A, TJ = 25 °C
7
Ω
IDRAIN = 0.2 A, TJ = 125 °C
14
Ω
Drain-source on state
resistance
Effective (energy related)
output capacitance
800
VDRAIN = 0 to 640 V
V
40
pF
Supply section
Parameter
Test condition
Min
Typ
Max
Unit
60
80
100
V
Voltage
VDRAIN_START
Drain-source start voltage
IDDch1
Charging current during the
start up
VDRAIN = 100 V to 640 V,
VDD = 4 V
-0.6
-1.8
mA
IDDch2
Charging current during the
autorestart
VDRAIN = 100 V to 640 V,
VDD = 9 V falling edge
-7
-13
mA
11.5
23.5
V
VDD
VDDclamp
VDDon
Operating voltage range
VDD clamp voltage
IDD = 15 mA
23.5
V
VDD start up threshold
12
13
14
V
VDDCSon
VDD on internal high voltage
current generator threshold
9.5
10.5
11.5
V
VDDoff
VDD under voltage shutdown
threshold
7
8
9
V
0.6
mA
2.5
mA
3.5
mA
0.35
mA
Current
IDD0
Operating supply current, not
switching
FOSC = 0 kHz,
VCOMP = GND
VDRAIN = 120 V,
IDD1
Operating supply current,
switching
FSW = 60 kHz
VDRAIN = 120 V,
FSW = 115 kHz
IDDoff
Operating supply current with
VDD < VDDoff
VDD < VDDoff
IDDol
Open loop failure current
threshold
VDD = VDDclamp
VCOMP = 3.3 V,
a. Adjust VDD above VDDon startup threshold before setting to 14 V
6/25
Doc ID 17736 Rev 2
4
mA
VIPER26
Table 8.
Electrical data
Controller section
Symbol
Parameter
Test condition
Min Typ Max Unit
Error amplifier
VREF_FB
IFB_PULL UP
GM
FB reference voltage
3.2
3.3
3.4
V
Current pull up
-1
µA
Trans conductance
2
mA/V
ILIM = -100 µA
0.5
V
3
V
Current setting (LIM) pin
VLIM_LOW
Low level clamp voltage
Compensation (COMP) pin
VCOMPH
Upper saturation limit
TJ = 25 °C
VCOMPL
Burst mode threshold
TJ = 25 °C
VCOMPL_HYS Burst mode hysteresis
HCOMP
TJ = 25 °C
Source / sink current
Max source current
1.1
1.2
V
40
mV
3
V/A
VFB = GND
15
kΩ
VFB > 100 mV
150
µA
VCOMP = GND, VFB = GND
220
µA
∆VCOMP / ∆IDRAIN
RCOMP(DYN) Dynamic resistance
ICOMP
1
Current limitation
IDlim
Drain current limitation
tSS
Soft-start time
TON_MIN
Minimum turn ON time
IDlim_bm
Burst mode current limitation
ILIM = -10 µA, VCOMP = 3.3 V, TJ = 25 °C 0.66 0.7 0.74
8.5
ms
480
VCOMP = VCOMPL
A
ns
145
mA
Overload time
50
ms
Restart time after fault
1
s
Overload
tOVL
tRESTART
Oscillator section
FOSC
VIPER26L
54
60
66
kHz
VIPER26H
103 115 127
kHz
FOSC = 60 kHz
±4
kHz
FOSC = 115 kHz
±8
kHz
230
Hz
Switching frequency
FD
Modulation depth
FM
Modulation frequency
DMAX
Maximum duty cycle
70
80
%
Thermal shutdown
TSD
THYST
Thermal shutdown temperature
Thermal shutdown hysteresis
Doc ID 17736 Rev 2
150 160
°C
30
°C
7/25
Typical electrical characteristics
VIPER26
5
Typical electrical characteristics
Figure 4.
IDlim vs TJ
Figure 5.
,'/,0,'/,0#&
)26&)26&#&
FOSC vs TJ
Figure 6.
VDRAIN_START vs TJ
Figure 7.
9'5$,1B67$579'5$,1B67$57#&
HCOMP vs TJ
+&203+&203#&
Figure 8.
GM vs TJ
Figure 9.
*0*0#&
VREF_FB vs TJ
95()B)%95(B)%#&
!-V
!-V
!-V
8/25
!-V
!-V
Doc ID 17736 Rev 2
!-V
VIPER26
Typical electrical characteristics
Figure 10. ICOMP vs TJ
Figure 11. Operating supply current
(no switching) vs TJ
,&203,&203#&
,'',''#&
!-V
!-V
Figure 12. Operating supply current
(switching) vs TJ
Figure 13. IDlim vs RLIM
,'',''#&
,'/,0,'/,0#.2KP
!-V
!-V
Figure 14. Power MOSFET on-resistance vs TJ Figure 15. Power MOSFET break down voltage
vs TJ
5'6215'621#&
%9'66%9'66#&
!-V
Doc ID 17736 Rev 2
!-V
9/25
Typical circuits
VIPER26
Figure 16. Thermal shutdown
VDD
VDDon
VDDCSon
VDDoff
time
IDRAIN
time
TJ
TSD
TSD - THYST
time
Normal operation
6
Normal operation
Shut down after over temperature
Typical circuits
Figure 17. Buck converter (VOUT>VDDCSon)
$
2FB
!# ).
$
2
,
6)0%2
$2 !).
6$$
$
&"
#
#
#
#FB
#/-0
2FB
#/. 42 /,
,)-
#
'.$
2COMP
2,)OPTIONAL #COMP
,OUT
$OUT
'2/5.$
6/54
#OUT
'2/5.$
!-V
10/25
Doc ID 17736 Rev 2
VIPER26
Typical circuits
Figure 18. Fly-back converter (isolated)
!#).
2
4
,
#C L 2C L
$
$
6OUT
$
$
2
!#).
#
6)0%2
$ 2!).
6$ $
#
2
#
#
&"
# /- 0
#
2REF # /. 4 2 /,
,)-
'.$
/04/
2
2
#
2
2,)-
#
)# #
2REF '2/5. $
'2/5. $
!-V
Figure 19. Flyback converter (primary regulation)
!-V
Doc ID 17736 Rev 2
11/25
Typical circuits
VIPER26
Figure 20. Flyback converter (non isolated, VOUTmVDDCSon)
2IN
,
!#).
$IN
#
#
2CL
#CL
6/54
$OUT
!#).
$
#OUT
$AUX
6)0%2
2FB
6$$
&"
2FB
#/-0
#
$2!).
#/.42/,
,)-
'.$
2COMP
#COMP
#COMP
2,)-
OPTIONAL
!-V
Figure 21. Flyback converter (non isolated, VOUT[VDDCSon)
12/25
Doc ID 17736 Rev 2
VIPER26
7
Power section
Power section
The power section is implemented with an n-channel power MOSFET with a breakdown
voltage of 800 V min. and a typical RDS(on) of 7 Ω. It includes a SenseFET structure to allow
a virtually lossless current sensing and the thermal sensor.
The gate driver of the power MOSFET is designed to supply a controlled gate current during
both turn-ON and turn-OFF in order to minimize common mode EMI. During UVLO
conditions, an internal pull-down circuit holds the gate low in order to ensure that the power
MOSFET cannot be turned ON accidentally.
8
High voltage current generator
The high voltage current generator is supplied by the DRAIN pin. At the first start up of the
converter, it is enabled when the voltage across the input bulk capacitor reaches the
VDRAIN_START threshold, sourcing the IDDch1 current (see Table 7 on page 6); as the VDD
voltage reaches the VDDon start-up threshold, the power section starts switching and the
high voltage current generator is turned OFF. The VIPer26 is powered by the external
source. After the start-up, the auxiliary winding or the diode connected to the output voltage
have to power the VDD capacitor with voltage higher than VDDCSon threshold (see Table 7
on page 6). During the switching, the internal current source is disabled and the
consumptions are minimized. In case of fault the switching is stopped and the device is self
biased by the internal high voltage current source; it is activated between the levels VDDCSon
and VDDon delivering the current IDDch2 to the VDD capacitor during the MOSFET off time,
see Figure 22 on page 13.
At converter power-down, the VDD voltage drops and the converter activity stops as it falls
below VDDoff threshold (see Table 7 on page 6).
Figure 22. Power on and power off
VIN
VIN < VDRAIN_START
HV startup is no more activated
VDRAIN_START
VDD
regulation is lost here
time
VDDon
VDDCSon
VDDoff
VDRAIN
time
IDD
time
IDDch2
IDDch1
Power-on
Normal operation
Doc ID 17736 Rev 2
Power-off
time
13/25
Oscillator
9
VIPER26
Oscillator
The switching frequency is internally fixed at 60 kHz (VIPER26LN or LD) or 115 kHz
(VIPER26HN or HD).
In both cases the switching frequency is modulated by approximately ±4 kHz (60 kHz
version) or ±8 kHz (115 kHz version) at 230 Hz (typical) rate, so that the resulting spreadspectrum action distributes the energy of each harmonic of the switching frequency over a
number of sideband harmonics having the same energy on the whole but smaller
amplitudes.
10
Soft start-up
During the converters' start-up phase, the soft-start function progressively increases the
cycle-by-cycle drain current limit, up to the default value IDlim. By this way the drain current is
further limited and the output voltage is progressively increased reducing the stress on the
secondary diode. The soft-start time is internally fixed to tSS, see typical value on Table 8 on
page 7, and the function is activated for any attempt of converter start-up and after a fault
event.
This function helps prevent transformers' saturation during start-up and short-circuit.
11
Adjustable current limit set point
The VIPer26 includes a current mode PWM controller: cycle by cycle the drain current is
sensed through the integrated resistor RSENSE and the voltage is applied to the non
inverting input of the PWM comparator, see Figure 2 on page 3. As soon as the sensed
voltage is equal to the voltage derived from the COMP pin, the power MOSFET is switched
OFF.
In parallel with the PWM operations, the comparator OCP, see Figure 2 on page 3, checks
the level of the drain current and switch OFF the power MOSFET in case the current is
higher than the threshold IDlim, see Table 8 on page 7.
The level of the drain current limit, IDlim, can be reduced depending from the sunk current
from the pin LIM. The resistor RLIM, between LIM and GND pins, fixes the current sunk and
than the level of the current limit, IDlim, see Figure 13 on page 9.
When the LIM pin is left open or if the RLIM has an high value (i.e. > 80 kΩ) the current limit
is fixed to its default value, IDlim, as reported on Table 8 on page 7.
14/25
Doc ID 17736 Rev 2
VIPER26
FB pin and COMP pin
The device can be used both in non-isolated and in isolated topology. In case of nonisolated topology, the feedback signal from the output voltage is applied directly to the FB
pin as inverting input of the internal error amplifier having the reference voltage, VREF_FB,
see the Table 8 on page 7.
The output of the error amplifier sources and sinks the current, ICOMP, respectively to and
from the compensation network connected on the COMP pin. This signal is then compared,
in the PWM comparator, with the signal coming from the SenseFET; the power MOSFET is
switched off when the two values are the same on cycle by cycle basis. See the Figure 2 on
page 3 and the Figure 23 on page 15.
When the power supply output voltage is equal to the error amplifier reference voltage,
VREF_FB, a single resistor has to be connected from the output to the FB pin. For higher
output voltages the external resistor divider is needed. If the voltage on FB pin is
accidentally left floating, an internal pull-up protects the controller.
The output of the error amplifier is externally accessible through the COMP pin and it’s used
for the loop compensation: usually an RC network.
As reported on Figure 23 on page 15, in case of isolated power supply, the internal error
amplifier has to be disabled (FB pin shorted to GND). In this case an internal resistor is
connected between an internal reference voltage and the COMP pin, see the Figure 23 on
page 15. The current loop has to be closed on the COMP pin through the opto-transistor in
parallel with the compensation network. The VCOMP dynamics ranges is between VCOMPL
and VCOMPH as reported on Figure 24 on page 16.
When the voltage VCOMP drops below the voltage threshold VCOMPL, the converter enters
burst mode, see Section 13 on page 16.
When the voltage VCOMP rises above the VCOMPH threshold, the peak drain current will
reach its limit, as well as the deliverable output power
Figure 23. Feedback circuit
Without Isolation:
switch open & E/A enabled
VREF
With Isolation:
switch closed & E/A disabled
VOUT
RCOMP
VCOMPL
+
PWM stop
-
SW
BUS
FB
from RSENSE
-
RH
VREF_FB
E/A
+
12
FB pin and COMP pin
+
Isolation
RL
nR
No
Isolation
to PWM
-
R
COMP
Doc ID 17736 Rev 2
15/25
Burst mode
VIPER26
Figure 24. COMP pin voltage versus IDLIM
,'5$,1
, 'OLP
,'OLPBEP
9&203/
9&203+
9&203
!-V
13
Burst mode
When the voltage VCOMP drops below the threshold, VCOMPL, the power MOSFET is kept in
OFF state and the consumption is reduced to IDD0 current, as reported on Table 7 on
page 6. As reaction at the energy delivery stop, the VCOMP voltage increases and as soon
as it exceeds the threshold VCOMPL + VCOMPL_HYS, the converter starts switching again with
consumption level equal to IDD1 current. This ON-OFF operation mode, referred to as “burst
mode” and reported on Figure 25 on page 16, reduces the average frequency, which can go
down even to a few hundreds hertz, thus minimizing all frequency-related losses and
making it easier to comply with energy saving regulations. During the burst mode, the drain
current limit is reduced to the value IDlim_bm (reported on Table 8 on page 7) in order to
avoid the audible noise issue.
Figure 25. Load-dependent operating modes: timing diagrams
VCOMP
VCOMPL +VCOMPL_HYS
VCOMPL
time
IDD
IDD1
IDD0
time
IDRAIN
IDlim_bm
time
Burst Mode
16/25
Doc ID 17736 Rev 2
VIPER26
14
Automatic auto restart after overload or short-circuit
Automatic auto restart after overload or short-circuit
The overload protection is implemented in automatic way using the integrated up-down
counter. Every cycle, it is incremented or decremented depending if the current logic detects
the limit condition or not. The limit condition is the peak drain current, IDlim , reported on
Table 8 on page 7 or the one set by the user through the RLIM resistor, as reported in
Figure 13 on page 9.
After the reset of the counter, if the peak drain current is continuously equal to the level IDlim,
the counter will be incremented till the fixed time, tOVL, after that will be disabled the power
MOSFET switch ON. It will be activated again, through the soft start, after the tRESTART time,
see the Figure 26 on page 17 and the mentioned time values on Table 8 on page 7.
In case of overload or short-circuit event, the power MOSFET switching will be stopped after
a time that depends from the counter and that can be as maximum equal to tOVL. The
protection will occur in the same way until the overload condition is removed, see Figure 26
on page 17.
This protection ensures restart attempts of the converter with low repetition rate, so that it
works safely with extremely low power throughput and avoiding the IC overheating in case of
repeated overload events.
If the overload is removed before the protection tripping, the counter will be decremented
cycle by cycle down to zero and the IC will not be stopped.
Figure 26. Timing diagram: OLP sequence
VDD
SHORT CIRCUIT
REMOVED HERE
SHORT CIRCUIT
OCCURS HERE
VDDon
VDDCSon
time
IDRAIN
IDlim_bm
t1*
tOVL
tRESTART
tOVL
tRESTART
tSS
tSS
time
tRESTART
tSS
* The time t1 can be lower or equal to the time tOVL
Doc ID 17736 Rev 2
17/25
Open loop failure protection
15
VIPER26
Open loop failure protection
In case the power supply is built in fly-back topology and the VIPer26 is supplied by an
auxiliary winding, as shown in Figure 27 on page 18 and Figure 28 on page 19, the
converter is protected against feedback loop failure or accidental disconnections of the
winding.
The following description is applicable for the schematics of Figure 27 on page 18 and
Figure 28 on page 19, respectively the non-isolated fly-back and the isolated fly-back.
If RH is opened or RL is shorted, the VIPer26 works at its drain current limitation. The output
voltage, VOUT, will increase and so the auxiliary voltage, VAUX, which is coupled with the
output through the secondary-to-auxiliary turns ratio.
As the auxiliary voltage increases up to the internal VDD active clamp, VDDclamp (the value is
reported on Table 8 on page 7) and the clamp current injected on VDD pin exceeds the
latch threshold, IDDol (the value is reported on Table 8 on page 7), a fault signal is internally
generated.
In order to distinguish an actual malfunction from a bad auxiliary winding design, both the
above conditions (drain current equal to the drain current limitation and current higher than
IDDol through VDD clamp) have to be verified to reveal the fault.
If RL is opened or RH is shorted, the output voltage, VOUT, will be clamped to the reference
voltage VREF_FB (in case of non isolated fly-back) or to the external TL voltage reference (in
case of isolated fly-back).
Figure 27. FB pin connection for non-isolated fly-back
2
#
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6$$
6$$
6/54
6
#/-0,
07-STOP
2(
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FROM2
3%.3%
%!
6
2,
TO07-
2%&?&"
N2
2
#/-0
2S
#P
#S
18/25
Doc ID 17736 Rev 2
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Open loop failure protection
Figure 28. FB pin connection for isolated fly-back
2
#
!58
$
!58
6!58
6$$
6
2%&?&"
2
COMP
07-ST OP
6
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37
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FROM2
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6
2%&?&"
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2
2OPTO
2
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2
5
2C
#C
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4,
2
,
Doc ID 17736 Rev 2
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Package mechanical data
16
VIPER26
Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
Table 9.
DIP-7 mechanical data
mm
Dim.
Typ
Min
A
5.33
A1
0.38
A2
3.30
2.92
4.95
b
0.46
0.36
0.56
b2
1.52
1.14
1.78
c
0.25
0.20
0.36
D
9.27
9.02
10.16
E
7.87
7.62
8.26
E1
6.35
6.10
7.11
e
2.54
eA
7.62
eB
10.92
L
3.30
M
2.508
N
0.50
N1
O
20/25
Max
2.92
3.81
0.40
0.60
0.60
0.548
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Package mechanical data
Figure 29. DIP-7 package dimensions
Doc ID 17736 Rev 2
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Package mechanical data
Table 10.
VIPER26
SO16N mechanical data
mm
Dim.
Min
Typ
A
1.75
A1
0.1
A2
1.25
b
0.31
0.51
c
0.17
0.25
D
9.8
9.9
10
E
5.8
6
6.2
E1
3.8
3.9
4
e
0.25
1.27
h
0.25
0.5
L
0.4
1.27
k
0
8
ccc
22/25
Max
0.1
Doc ID 17736 Rev 2
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Package mechanical data
Figure 30. SO16N package dimensions
Doc ID 17736 Rev 2
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Revision history
17
VIPER26
Revision history
Table 11.
24/25
Document revision history
Date
Revision
Changes
26-Aug-2010
1
Initial release.
01-Sep-2010
2
Updated Figure 30 on page 23.
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