Achieving High Accuracy Voltage with the DCM

APPLICATION NOTE | AN:035
Achieving High Accuracy Voltage (or Current) Regulation
with the DCM Up to ± 1% regulation
Xiaoyan Yu
Applications Engineering
August 2015
ContentsPage
Introduction
Loop Compensation
The DC-DC Converter Module (DCM) provides isolation, regulation, fault protection
and monitoring in a single module. Through a negative slope load line and temperature
coefficient, DCM arrays implement wireless current sharing. In either single DCM circuits
2 or in arrays, the nominal load regulation is about 5% (see the %V
OUT-LOAD specification
in the DCM data sheet), excluding other regulation error terms. This may not be sufficient
3 for applications that have tight voltage regulation requirements. In those applications, an
isolated analog feedback loop, such as the one shown in Figure 1, can be used to improve the
load regulation performance. The circuit shown here is recommended for general use in high
5 accuracy applications that need to preserve the input-output isolation offered by the DCM.
The circuit is applicable to single DCMs as well as arrays of up to eight units.
6
Experimental Results
8
Introduction1
Circuit Schematic
Functional Description
Remote Sense Circuit
Component Selection
Conclusion10
Appendix I
11
Appendix II
12
For array applications, on the primary side, after any needed differential-mode filtering, the
DCMs must share a common –IN node, which is also the ground reference for the remote
sense sub circuit output. The DCM TR pins are all driven by single output of the remote sense
sub circuit, so it is important to minimize voltage differences between the various DCM –IN
pins through careful layout techniques. On the secondary side, the remote sense sub circuit
senses the output voltage through the R1/R2 resistor network, compares that to a reference
voltage, and converts the error voltage into a trim voltage for the whole array.
Since the DCMs are all effectively programmed to the same trim voltage, the current sharing
between modules is still the same as it would be without the remote sense circuit, as covered
in AN030: Parallel DCMs.
This circuit works with all ChiP DCM types, and achieves a regulation accuracy of ±1%
at all line, load, temperature, and trim conditions.
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Circuit Schematic
Figure 1.
Remote Sense Circuit for DCM
Module 1
RTRIM_1
TR
EN
FT
+IN
+IN
+OUT
+OUT
-IN
-IN
-OUT
-OUT
RTRIM_2
Module 2
TR
EN
FT
≈≈
+IN
+OUT
-IN
-OUT
≈≈
≈
Module N
RTRIM_N
TR
EN
FT
+IN
+OUT
-IN
-OUT
PRI-GND
EMI-GND
SEC-GND
VOUT
VTR
U3
CNY17-3
5
C5
1nF
5VFILT
L1
LQH32CN330
1
R7
VEAO 1
2
4
R6
400Ω
PRI-SGND
5
U2 2
MAX4238
U1
ADR361
VREF
6
2.5V
3
4
C1
4
VO VIN 3
GND
2
R8
1kΩ
1
U4
LM2936HVMAX-5.0*
8
VO VIN
7
GND
C9
6
GND
0.1uF
C6/C7/C8
C2012X6S1H475
R3
R1
2.2uF (120 kΩ/N) – (R1||R2)
ECW-FD2W225J
Remote sense circuit
C2
10uF
5V
SEC-SGND
(VOUT-2.5)*R1/2.5
R2
10kΩ
*See Table 1
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Functional Description of Remote Sense Circuit
The output voltage is sensed through resistor network R1 and R2 relative to secondary
ground SEC-SGND; the sensed voltage becomes
R2
VOUT •
(1)
R1 + R2
1. The sensed voltage is compared to the reference voltage VREF, which in this schematic
is generated by the 2.5 V reference U1.
VREF = 2.5 V
(2)
If another VREF voltage is preferred, VREF is recommended to be between 1.5 V and 3 V for
optimum noise immunity.
2. The difference gets accumulated by an integrating error amplifier (consisting of R3, C1
and U2), which generates VEAO.
3. The difference between VEAO and 5 VFILT drives the input of the optocoupler U3.
4. The optocoupler (U3) is used to preserve the galvanic isolation of the DCM array.
5. The output of U3 is its collector current. That current develops a voltage drop across the
RTRIM_x and RTRIM-INT_x resistors and establishes the DCM trim pin voltages.
(The RTRIM-INT_x are the internal pull-up resistors inside each DCM. Each RTRIM-INT_x
pulls up to VCC, the DCM’s internally generated 3.3 V supply.) Figure 2 details how the
trim pin voltages are generated, along with a simplified model for N DCMs in parallel.
The RTRIM_x resistors are all the same nominal value, as are all of
the RTRIM-INT_x resistors.
Figure 2.
Trim Voltage
Generation Method
and It's Simplified Model
DCM1
RTRIM-INT_1
RTRIM_1
3.3V
VTR’_1
DCM2
RTRIM-INT_2
RTRIM_2
VTR’_2
3.3V
3.3V
VTR’_N
U3
VTR
VTR
VTR
5VFILT
5
1
4
2
C5
R7
PRI-SGND
RTRIM-INT_x / N
VTR’
DCMN
RTRIM-INT_N
RTRIM_N
C5
RTRIM_x/N
3.3V
Optocoupler
R6
U3
VTR
5VFILT
1
4
2
R7
Optocoupler
R6
VEAO
VEAO
6.
VTR
5
If the sensed version of VOUT is less than VREF, the error amplifier output rises, and the
drive current into the optocoupler’s LED is reduced. This in turn reduces the
optocoupler’s (output) collector current, permitting the pull-up resistors to pull the
trim voltage higher, which raises each DCMs programmed output trim voltage.
Conversely, if VOUT is too high, the DCM trim pin voltages are similarly driven lower,
which lowers VOUT.
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7. R6 is chosen to set the voltage transfer ratio of the optocoupler, to ensure that it operates
as expected over temperature and with age (see Appendix I).
8. R7 establishes a minimum load on the TR pins by setting the maximum trim
bus voltage.
a. R7 must be chosen so that the maximum trim voltage will be below the TR trim
enable threshold, even with no optocoupler current; some margin is needed so that
trim remains enabled in the presence of noise.
b.
The value of R7 may be further reduced, to limit the maximum trim voltage, which
can be helpful in reducing overshoot during load transients and startup.
For N DCMs in parallel, the trim voltage input to the DCM, VTR’_x (see Figure 2), can
be calculated as:
VTR’max = 3.3 •
N • R7 + RTRIM_x
N • R7 + RTRIM_x + RTRIM-INT_x
(3)
Where RTRIM_x = 301 Ω, RTRIM-INT_x = 10 kΩ as specified in the DCM datasheet, N is the number of DCMs in parallel.
Thus the maximum trim voltage input can be calculated as:
VTR’max = 3.3 •
N • R7 + 10301
(4)
For example, if the trim voltage is to be limited to 3 V, the value of R7 can be chosen as:
R7 =
N • R7 + 301
100 kΩ
N
(5)
C5 is a low value ceramic capacitor, such as 1 nF, which is used to exclude high frequency noise from VTR.
9. The bus that is used to supply U1, U2 and U3 is generated from VOUT. Through this
method, no external 5 V power supply is needed.
U4 regulates VOUT to an unfiltered 5 V, which is called 5 V in Figure 1. This 5 V then goes
through the filter network (C2, L1, C6-C8) and becomes a filtered 5 V, which is called
5 VFILT. R8 discharges the filter capacitors when VOUT is off. The output of this circuit is
the 5 VFILT bus that supplies U1, U2 and U3.
10.
Optionally, U4/C6-C8/L1/C2/R8 can be removed from the circuit if a precision external
5 V power supply with at least 50 mA capability is available to drive the 5 VFILT bus.
The benefit of using an external 5 V power supply is that it uses fewer components. The
disadvantage is that if the external supply is energized before the DCMs are enabled,
then the error amplifier will “wind up” to a maximum trim condition. When the DCM
are started, the system output voltage will significantly overshoot the setpoint until the
integrator unwinds. When using an external 5 V power supply, R7 should be chosen
carefully so that VOUT does not exceed the maximum voltage allowed by the application,
or the DCMs should be enabled prior to energizing the external 5 V supply node.
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Through this method, the output voltage of the DCM can be trimmed to:
VOUT = VREF •
R1 + R2
(6)
R2
The maximum cut off frequency of the whole loop is 30 Hz, but with CTR variance,
temperature, and aging of the optocoupler, it can be as low as approximately 7.5 Hz.
Table 1.
VOUT
Notes for the Choice of U4
U4 Recommendation
6 V ≤ VOUT ≤ 60 V
Use LM2936HVMAX-5.0 for U4
VOUT ≤ 6 V
Use an appropriate regulator for
U4 so that the output voltage of
U4 will be between 4 V and
5.5 V, or use an independent
supply rail in the application
Comment
For DCM modules with a rated VOUT-NOM of 5 V
or 3.3 V, for example.
Component Selection
The following resources can be used to facilitate the selection of filter network components:
n Each DCM’s datasheet
n AN030: Parallel DCMs
(www.vicorpower.com/documents/application_notes/an_Parallel_DCMs.pdf)
n Powerbench Filter Design Tool
(app2.vicorpower.com/filterDesign/intiFilter.do)
n AN023: Filter Network Design for DC-DC Converter Modules
(www.vicorpower.com/documents/application_notes/vichip_appnote23.pdf)
The detailed schematic of the DCM remote sense circuit has been shown in Figure 1, with IC
device types and component values. The generic components’ part numbers have not been
marked in the schematic. Unconnected pins have not been shown for simplicity.
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The recommended components for the remote sense circuit are summarized here (excluding
the generic components):
Table 2.
Part ID
Recommended Components for
Remote Sense Circuit
Type
Manufacturer
Part Number
Digi-Key
Part Number
Note
C1
CAP FILM 2.2 UF
450 VDC RADIAL
ECW-FD2W225J
PCF1609-ND
Low leakage, low
dielectric absorption
U1
IC VREF SERIES 2.5 V
TSOT23-5
ADR361BUJZ-REEL7
ADR361BUJZREEL7CT-ND
High precision
U2
IC OPAMP GP 1 MHZ
RRO SOT23-6
MAX4238AUT+T
MAX4238AUT+
TDKR-ND
Low input offset voltage, low input
offset current, low supply consumption, but not necessarily high
bandwidth or high slew rate
U3
OPTOISO 5 KV
TRANS W/BASE
6SMD
CNY17-3X017T
CNY173X017TCT-ND
5 kV isolation;
Current Transfer Ratio no less than
100% @ 10 mA
U4
IC REG LDO 5 V
50 MA 8SOIC
LM2936HVMAX-5.0/NOPB
LM2936HVMAX-5.0/
NOPBCT-ND
See Table 1
C6/C7/C8
CAP CER 4.7 UF 50 V
20% X6S 0805
C2012X6S1H475M125AC
445-7600-1-ND
L1
IC VREF SERIES 2.5 V
TSOT23-5
ADR361BUJZ-REEL7
ADR361BUJZREEL7CT-ND
High precision
R1, R2 and R7 may vary according to the application and DCM module. Consider the
following before choosing these values:
a. R1/R2 = VOUT/VREF -1, VOUT is the trimmed DCM output voltage.
b. Choose high accuracy resistors (up to 0.1% accuracy) for R1 and R2; their accuracy
directly relates to the resultant output voltage setpoint.
VOUT-2.5
• R2
c. Choose R2 = 10 kΩ; then the resistance of R1 can be calculated as: R1 =
2.5
This will minimize current consumption and power dissipation
in the divider network, while maintaining good immunity from noise and effects of
bias currents from amplifier input. With R2 being fixed at 10 kΩ, a high accuracy
resistor value for R1 may not be available. In that case, the nominal value of R2 can
be adjusted to be within +/-10% of 10 kΩ.
d. R7 limits the maximum programmed trim for the DCMs. Use Equation (3) to
determine the value of R7.
Loop Compensation
When trim is active, the DCM TR pin provides dynamic trim control of the module’s output
voltage with at least 30 Hz of (small signal) control bandwidth over the output voltage of the
DCM converter. The phase shift at 30 Hz is approximately 45°.
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The whole open loop transfer function at 30 Hz or below can be calculated as:
A (s) = ATR (s) •
R2
•
R2 + R1
1
R3’ • C1 • s
• CTR •
RTRIM-INT_x
N • R6
(7)
Where CTR is the Current Transfer Ratio of the optocoupler, which is specified in the
optocoupler data sheet;
R3’ = R3 +
R1 • R2
; recall that N is the number of DCM modules in parallel.
R1 + R2
For frequencies less than or equal to 30 Hz, the analysis is as follows:
ATR (s) is the transfer function from TR to VOUT, which is a constant ATR at very low
frequency and ≤ ATR at 30 Hz.
VOUT •
R2
R1 + R2
= 2.5
(8)
Rearranging the equality:
R2
=
R2 + R1
2.5
(9)
VOUT
Multiplying both sides by ATR (s),
ATR (s) •
R2
=
R2 + R1
2.5 • ATR (s)
(10)
VOUT
2.5 • ATR (s)
The term
VOUT
increases with increasing trim range. For existing DCMs, the widest
trim range is −40% to 10% of VOUT_NOM. For these DCMs,
2.5 • ATR
VOUT_MIN
≈1
Therefore:
ATR (s) •
R2
≤1
R2 + R1
(11)
Inserting this result into Equation (7):
A(s) ≤ 1 •
1
R3’ • 2.2 µF • s
• CTR •
10 kΩ
N • 400
(12)
If R3 is chosen so that A(s) goes to 0 dB at 30 Hz, the whole system will have approximately
45° phase margin.
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Setting A(s) to 0 dB at 30 Hz results in:
60 kΩ • CTR
R3’ =
(13)
N
For the optocoupler used in the schematic, the maximum CTR is in the range of 1 to 2. So for
the worst case gain, CTR = 2:
R3’ =
R3 =
120 kΩ
(14)
N
120 kΩ
N
–
R1 • R2
(15)
R1 + R2
Experimental Results (Steady State, Startup, and Transient)
Steady State Load Regulation
Using the DCM300P480T500A40 as an example, experimental results for a single DCM are
shown in Figure 3; the results for an array of eight DCMs are shown in Figure 4.
Figure 3.
The Experimental Results for
Single DCM300P480T500A40
with this Remote Sense Circuit
Low Trim
High Trim
0.25
VOUT Regulation Error (%)
VOUT Regulation Error (%)
0.25
0.15
0.05
-0.05
-0.15
0.15
0.05
-0.05
-0.15
-0.25
-0.25
0
20
40
60
80
0
100
20
Low Line
40
60
80
100
80
100
Rated Load (%)
Rated Load (%)
Low Line
Nom Line
Nom Line
High Line
High Line
Figure 4.
Experimental Results for an 8-up
DCM300P480T500A40 Array
with this Remote Sense Circuit
Low Trim
0.15
0.05
-0.05
-0.15
-0.25
0.15
0.05
-0.05
-0.15
-0.25
0
20
40
60
80
Rated Load (%)
Low Line
Nom Line
High Line
High Trim
0.25
VOUT Regulation Error (%)
VOUT Regulation Error (%)
0.25
AN:035
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0
20
40
60
Rated Load (%)
Low Line
Nom Line
High Line
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Startup
Typical startup waveforms are shown in Figure 5 and Figure 6. During startup, once VOUT
reaches U4’s minimum input voltage, U4 will generate the 5 V bus to supply U1, U2 and U3.
The waveform of the startup typically comes in two stages: in the first stage, VOUT rises to the
minimum trimmed VOUT; in the second stage, the circuit comes to the steady state and brings
VOUT to the correct trimmed value.
This circuit needs to be started up after VOUT and the 5 V bus have fully discharged to avoid
trimming to the highest VOUT.
Figure 5.
Experimental Results for a Single
DCM300P480T500A40 (low
line, maximum external COUT)
Startup into High Trim with this
Remote Sense Circuit
(a) 10% Load
(b) Full Load (Electronics Load in CR Mode)
(a) 10% Load
(b) Full Load (Electronics Load in CR Mode)
Figure 6.
Experimental Results for a single
DCM300P480T500A40 (high
line, maximum external COUT)
Startup into Low Trim with this
Remote Sense Circuit
Load Transient Response
There is a delay from the transient until the circuit reaches the corrected output voltage,
which is due to the limited bandwidth of the DCM TR pin and remote sense circuit. Because
of this narrow bandwidth, the remote sense circuit doesn’t affect the initial response to a
transient. Figure 7 shows a comparison of transient response without the remote sense
circuit to the response with the remote sense circuit in operation.
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Figure 7.
Comparison of a Single
DCM300P480T500A40
Transient Response (nominal
line, nominal trim, electronic
load in CC mode 10% to 100%
load transient) without the
Remote Sense Circuit and with
the Circuit Included
(a) Without Remote Sense Circuit
(b) With Remote Sense Circuit
Conclusion
Using the remote sense circuit shown here, DCM-based voltage regulators can achieve
output voltage accuracy of ±1%. Within the 30 Hz bandwidth of the circuit, other aspects of
DCM operation are unchanged. This method works for any number of DCMs in parallel,
up to eight.
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Appendix I. Choosing R6 to Account for CTR Variance in the CNY17-3 Over
Temperature and Time
1. Information from Vishay CNY17 datasheet
(www.vishay.com/docs/83606/cny17.pdf):
PARAMETER
(Tamb = 25 °C, unless otherwise specified)
TEST CONDITION
PART
CNY17-1
CNY17-2
CNY17-3
CNY17-4
CNY17-1
CNY17-2
CNY17-3
CNY17-4
VCE = 5 V, IF = 10 mA
IC/IF
1.8
1.7
Tamb = 25 °C
1.6
Tamb = 0 °C
1.5
1.4
Tamb = - 25 °C
1.3 T = - 55 °C
amb
1.2
1.1
Tamb = 50 °C
1.0
Tamb = 75 °C
0.9
Tamb = 100 °C
0.8
0.7
Tamb = 110 °C
0.6
0.1
1
10
100
IF - Forward Current (mA)
1.2
CTRNorm - Normalized CTR (NS)
VF - Forward Voltage (V)
VCE = 5 V, IF = 1 mA
1.0
0.8
0.6
MIN.
40
63
100
160
13
22
34
56
IF = 10 mA
VCE = 5 V
Tamb = 25 °C
Tamb = 0 °C
Tamb = - 40 °C
Tamb = - 55 °C
0.4
Tamb = 50 °C
Tamb = 75 °C
Tamb = 100 °C
0.2
0
0.1
SYMBOL
CTR
CTR
CTR
CTR
CTR
CTR
CTR
CTR
Tamb = 110 °C
1
10
100
IF - Forward Current (mA)
Fig. 5 - Forward Voltage vs. Forward Current
Fig. 11 - Normalized CTR (NS) vs. Forward Current
TYP.
MAX.
80
125
200
320
30
45
70
90
1.2
CTRNorm - Normalized CTR (sat)
CURRENT TRANSFER RATIO
1.0
0.8
0.6
IF = 10 mA
VCE = 0.4 V
Tamb = 25 °C
Tamb = 0 °C
Tamb = - 40 °C
Tamb = - 55 °C
Tamb = 50 °C
0.4
0.2
0
0.1
UNIT
%
%
%
%
%
%
%
%
Tamb = 75 °C
Tamb = 100 °C
Tamb = 110 °C
1
10
100
IF - Forward Current (mA)
Fig. 12 - Normalized CTR (sat) vs. Forward Current
Tables and Figures courtesy of Vishay Intertechnology, Inc.
2. Calculation of CNY17-3 controller current achievable over temperature and time:
n Choosing R6 = 400 Ω, a supply voltage of 4 V (the lowest value specified in Table 1),
CTR = 100% and estimating the voltage drop across the optocoupler at 1.28 V, the
maximum forward current that the secondary side of the remote sense circuit could
have over the full temperature range is approximately (4 V − 1.28 V)/400 Ω = 6.8 mA.
n The next step is to find the minimum CTR at IF = 6.8 mA, using linear interpolation
on the data in the table for IF = 1 mA and IF = 10 mA. This results in a minimum CTR
of ((10 mA − 6.8 mA) · 34% + (6.8 mA − 1 mA) · 100%)/(10 mA – 1 mA) = 76.5% at 25⁰C
n From the Normalized CTR curves above, CTR could decrease to 60% of its peak value
n From Vishay reliability data, CTR is reduced by 15% over 8000 operation hours,
operation with aging.
n Since 3.3 V – (2.65 V · 1.25) = −0.01 V < 0 V, this will result in a trim voltage close to
giving CTR = 45.9% · (1 − 15%) = 39%
n Thus the collector current will be at least 6.8 mA · 39% = 2.65 mA, to ensure proper
over temperature, which is 76.5% · 60% = 45.9%
0 V, which is sufficient to drive all DCMs to trim low.
n When the forward current is small, the CNY17-3 will be able to drive all DCMs to
high trim, so high trim is achievable for any choice of R6.
Thus R6 = 400 Ω should be a valid choice for this circuit to work over temperature and time,
from single DCMs through arrays of eight DCMs.
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Appendix II. Current Regulation
If current regulation is needed instead of voltage regulation, with some modifications, the
remote sense circuit can be adapted to regulate a constant-current output.
Instead of sensing the output voltage with R1 and R2, a shunt resistor is used to measure the
output current. The voltage across the shunt resistor is sensed with an additional differential
amplifier stage, which feeds R3. R1 and R2 are not present, since the current signal scaling
is accomplished by current sense amplifier. The rest of the circuit is unchanged. A typical
schematic with the current sense sub-circuit is shown in Figure 8.
Notice that current regulation needs to be limited to the minimum rated output current
(IOUT) of the DCM, to avoid interfering with the DCM’s operational current limit and cause
issues.
In applications such as battery charging, the actual VOUT can be different from the trimmed
voltage of the DCM. Additional considerations may be needed:
1. The DCM has a minimum VOUT before it might detect output under voltage. For
example, the DCM would not be able to charge a battery whose voltage is
below VOUT_UVP.
2. The DCM current capability is reduced when the DCM is trimmed higher than nominal (regardless of the actual VOUT), so the output current from the system should be no
higher than n · (Rated POUT/maximum VOUT-TRIMMING) to avoid entering current limit.
The transfer function between the output current IOUT and the sense voltage VSENSE in
Figure 8 is:
VSENSE = IOUT • R8 • R9 • Gm
(16)
With an LMP8645HV, the typical Gm is 200 µA/V.
Through this method, the total output current of the DCMs can be trimmed to:
IOUT = VREF •
1
R8 • R9 • Gm
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Figure 8.
Remote Sense Circuit for DCM
for Current Regulation with
Single Current Sense Shunt
Module 1
RTRIM_1
TR
EN
FT
+IN
+IN
+OUT
IOUT
R8
-IN
-IN
RTRIM_2
+OUT
-OUT
-OUT
Module 2
U5
LMP8645HV
3
4
+IN
-IN
2
5
VRG
1
6
VOUT V+
TR
EN
FT
+IN
+OUT
-IN
-OUT
5VFILT
C10
0.1uF
R9
VSENSE
≈≈
Current sense subcircuit
≈≈
≈
Module N
RTRIM_N
TR
EN
FT
+IN
+OUT
-IN
-OUT
PRI-GND
EMI-GND
SEC-GND
VOUT
VTR
U3
CNY17-3
C5
1nF
5VFILT
5
1
4
2
R7
VEAO 1
R6
400Ω
PRI-SGND
5
U2 2
MAX4238
L1
LQH32CN330
U1
ADR361
VREF
6
2.5V
3
4
4
VO VIN 3
GND
2
C2
10uF
2.2uF
ECW-FD2W225J
R8
1kΩ
1
U4
LM2936HVMAX-5.0*
8
VO VIN
7
GND
C9
6
GND
0.1uF
C6/C7/C8
C2012X6S1H475
R3
C1
5V
SEC-SGND
(120/N)kΩ
Remote sense circuit
*See Table 1
In high current applications, individual current sense resistors for each DCM output may be
preferred (as shown in Figure 9) over using a single high-dissipation current sense resistor
for the entire DCM array. With R81, R82, … R8N all equal to R8, and R91, R92, … R9N all
equal to R9, the total output current of the DCMs can be trimmed to:
IOUT = VREF •
1
R8 • R9 • Gm
AN:035
vicorpower.com (18)
Applications Engineering: 800 927.9474
Page 13
Figure 9.
Remote Sense Circuit for DCM
for Current Regulation with
Individual Current Sense Shunts
Module 1
RTRIM_1
TR
EN
Current sense subcircuit
FT
+IN
+IN
+OUT
-IN
-IN
-OUT
U51
LMP8645HV
3
4
+IN
-IN
2
5
VRG
1
6
VOUT V+
Module 2
RTRIM_2
TR
EN
+IN
+OUT
-IN
-OUT
≈
≈≈
Module N
RTRIM_N
-OUT
5VFILT
R91
C101
0.1uF
FT
VSENSE_1
R82
IOUT_2
U52
LMP8645HV
4
3
+IN
-IN
5
2
VRG
6
1
VOUT V+
5VFILT
TR
≈≈
C102
0.1uF
EN
+OUT
IOUT_1
R81
R92
VSENSE_2
FT
+IN
+OUT
-IN
-OUT
PRI-GND
EMI-GND
R8N
IOUT_N
U5N
LMP8645HV
4
3
+IN
-IN
5
2
VRG
6
1
VOUT V+
5VFILT
SEC-GND
C101
0.1uF
R9N
VSENSE_N
VTR
VOUT
U3
CNY17-3
5
C5
1nF
5VFILT
1
R7
VEAO 1
2
4
R6
400Ω
PRI-SGND
5
U2 2
MAX4238
VREF
6
2.5V
3
4
C1
2.2uF
ECW-FD2W225J
Remote sense circuit
L1
LQH32CN330
U1
ADR361
VO VIN 3
4
GND
2
C2
10uF
C6/C7/C8
C2012X6S1H475
U4
LM2936HVMAX-5.0*
1 VO VIN 8
7
GND
C9
6
R8
GND
0.1uF
1kΩ
5V
SEC-SGND
R3N
(120/N)kΩ
R32
(120/N)kΩ
R31
(120/N)kΩ
*See Table 1
The Power Behind Performance
Rev 1.0
10/15
vicorpower.com Applications Engineering: 800 927.9474
Page 14
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