SEMTECH SC4910AITSTRT

SC4910A/B
High Performance Secondary Side
Controller with Synchronous Rectifier
POWER MANAGEMENT
Description
Features
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The SC4910A/B is an integrated, full featured, secondary side controller designed for use in single ended and
isolated switch mode power supplies with synchronous
rectification where efficiency and fast transient response
are of primary concern. The SC4910A/B has outputs for
both primary FET and secondary synchronous rectification. The primary drive output is designed to drive a small
and low cost pulse transformer to isolate the primary
FET driver. The secondary control makes it much easier
to monitor and control the system load with tight control
loops and implement load current sharing and synchronous rectification.
Synchronous rectification with adaptive control
Programmable secondary side delay
Programmable switching frequency
Programmable max. duty cycle
Remote voltage sense capability
Close-loop soft start with active low shutdown
0.75V precision reference for low output applications
Oscillator sychronization
Undervoltage Lockout
Operation to 1MHz
Current-mode or voltage-mode operation
Single stage power conversion with multiphase link
capability (with SC4201)
‹ Monotonic start-up with pre-biased output
‹ Active current sharing capability
‹ 20 pin TSSOP package
The SC4910A/B features synchronous rectification, multiphase link capability, programmable secondary side
delay, programmable switching frequency and programmable maximum duty cycle. It is designed for either
current mode or voltage mode operation.
Applications
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The SC4910A has a typical turn-on threshold of 9V and
the SC4910B has a threshold of 4.5V.
Typical Application Circuit
Telecom isolated DC to DC converters
Isolated VRMS
Networking power supplies
Industrial power supplies
Distributed power architectures
High density power modules
L1
+Vin
T1
C3
R2
R1
C1
LOAD
C2
M1
D1
M2
SC1301
SC1301
+12V
SC1301
C4
M3
SC4910
12
T2
D2
4
10
R3
R4
20
R5
19
3
15
5
PVCC
CS
C8
T3
C10
14
AVCC 16
ISHARE
PVCC
OUTA
PHASE
RT1
OUTB
RT2
COMP
SS
FB
SYNC/EN
DELAY
VREF
AGND
C9
13
7
-SENSE
PGND
8
6
11
C5
17
18
C6
R6
R7
2
1
R8
PGND
9
R9
D3
Revision: June 1, 2005
1
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SC4910A/B
POWER MANAGEMENT
Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified
in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device
reliability.
Parameter
Symbol
Maximum
Units
V cc
18
V
Output Voltage
V cc
V
Phase
V cc
V
-0.3 to 7
V
150
mA
Supply Voltage
FB, COMP, SYNC/EN, ISHARE
OUTA & OUTB Current Source or Sink
Junction Temperature Range
TJ
-40 to +150
°C
Storage Temperature Range
TSTG
-60 to +150
°C
Lead Temperature (Soldering) 10 Sec.
TLEAD
260
°C
Electrical Characteristics
Unless specified: TA = T = -40°C to 125°C , VCC = 12V, R = R = 50K, R
J
Parameter
T1
T2
DELAY
Test Conditions
= 50K, C
SS
= 0.1µF.
Min
Typ
Max
Unit
10
15
mA
Pow er Supply
Operating Current
SYNC/EN = Low
Undervoltage Lockout
Start Threshold
UVLO Hysteresis
S C 4910A
8.7
9.0
9.3
V
S C 4910B
4.35
4.50
4.75
V
S C 4910A
400
550
700
mV
S C 4910B
200
300
375
mV
S C 4910A
4.75
5.0
5.25
V
S C 4910B
2.97
3.30
3.63
V
VREF Reference
Output Voltage
Line Regulation
9.3V < Vcc < 15V
15
30
mV
Load Regulation
0mA < IREF < 5mA
2
10
mV
Soft Start
SS Output
0.75
Voltage Accuracy
Line Regulation
Impedance
TA = TJ = 25°C
9.3V < Vcc < 15V
 2005 Semtech Corp.
-1
+1
-1.5
+1.5
-5
0
7K
(2)
2
V
+5
%
mV
Ω
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SC4910A/B
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: TA = T = -40°C to 125°C , VCC = 12V, R = R = 50K, R
J
T1
Parameter
T2
DELAY
= 50K, C
SS
= 0.1µF.
Test Conditions
Min
Typ
Max
Unit
0.1
5
µA
Offset Voltage
2
7
mV
Open Loop Gain
80
dB
CMRR
70
dB
70
dB
1.9
V
Error Amplifier
Input Bias Current
PSRR
(1)
(1)
Output High Voltage
ICOMP = 1.0mA
Output Low Voltage
ICOMP = 1.0mA
Unity Gain Bandwidth (1)
1.75
0.9
1.0
MHz
5.0
Slew Rate (1)
V
2.0
V/µS
Min. Frequency RT1 = RT2 = 500K
50
KHz
Max. Frequency RT1 = RT2 = 25K
1000
Oscillator
Frequency Range
Frequency
Peak Voltage
450
(1)
Valley Voltage
(1)
Enable Input High
500
550
KHz
2.5
V
1.0
V
V
2.0
Enable Input Low
0.8
V
Duty Cycle
Maximum Duty Cycle
(2)
Minimum Duty Cycle
Duty Cycle Tolerance
90
%
0
%
-5
+5
%
Current Limit
Cycle by Cycle Threshold
Shutdown Threshold
0.975
1.025
1.075
V
1.1
1.25
1.4
V
Delay to Output (2)
100
nS
Input Impedance
20
kΩ
(2)
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SC4910A/B
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: TA = T = -40°C to 125°C , VCC = 12V, R = R = 50K, R
J
T1
Parameter
T2
DELAY
= 50K, C
Test Conditions
SS
= 0.1µF.
Min
Typ
Max
Unit
1
1.3
V
OUTA and OUTB
Output Low
IOUTPUT = 100mA
Output High
IOUTPUT = 100mA
Rise Time
(2)
Fall Time (2)
10
V
COUT = 100pF
20
nS
COUT = 100pF
20
nS
RDELAY = 50KΩ
70
nS
PHASE > 1.5V
220
nS
PHASE < 1.5V
30
9.75
Delay
OUTB Falling to OUTA Rising
OUTA Falling to OUTB Rising
(2)
(2)
Current Share Error Amplifier
Transconductance
(1)
Output Source or Sink Current (1)
0.18
mS
10
µA
Notes:
(1) Guaranteed by design.
(2) Guaranteed by characterization.
(3) This device is ESD sensitive. Use of standard ESD handling requirements are required.
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SC4910A/B
POWER MANAGEMENT
Pin Configurations
Ordering Information
Part Number
TOP VIEW
SC4910AITSTRT(2)
-SENSE
1
20
RT1
SYNC/EN
2
19
RT2
SS
3
18
FB
CS
4
17
COMP
VREF
5
16
ISHARE
PHASE
6
15
DELAY
AGND
7
14
AVCC
PGND
8
13
PVCC
PGND
9
12
PVCC
OUTA
10
11
OUTB
SC4910BITSTRT(2)
P ackag e
TSSOP-20(1)
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
(20 Pin TSSOP)
Marking Information
Part Number (Example: 1471)
yyww = Date Code (Example: 0012)
xxxxx = Semtech Lot No. (Example: P94A01)
Part Number (Example: 1471)
yyww = Date Code (Example: 0012)
xxxxx = Semtech Lot No. (Example: P94A01)
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SC4910A/B
POWER MANAGEMENT
Pin Descriptions
Pin #
Pin Name
1
-SENSE
Remote voltage sense return.
2
SYNC/EN
Bidirectional synchronization and enable /disable pin. Referenced to -SENSE.
3
SS
Soft start.
4
CS
Current sense input.
5
VREF
6
PHASE
Phase node for synchronous rectification.
7
AGND
Analog ground.
8
PGND
Power ground for OUTA.
9
PGND
Power ground for OUTB.
10
OUTA
Output driver for primary MOSFET and secondary forward MOSFET. Low during UVLO.
11
OUTB
Output the MOSFET driving signal for forward rectifier. Low during UVLO.
12
PVC C
Power supply for OUTB.
13
PVC C
Power supply for OUTA.
14
AVCC
Analog supply voltage.
15
DELAY
Predictive delay between OUTA and OUTB. The delay is from turn-off of the freewheeling
MOSFET to turn-on of the forward MOSFET and primary MOSFET. The delay time is 20 to
200nS programmable.
16
ISHARE
Current share bus.
17
COMP
18
FB
F e e d b a ck.
19
RT2
Connect to timing resistor RT2 to control the negative ramp of the internal oscillator.
20
RT1
Connect to timing resistor RT1 to control the positive ramp of the internal oscillator.
 2005 Semtech Corp.
Pin Function
5V internal reference output.
Feedback compensation.
6
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SC4910A/B
POWER MANAGEMENT
Block Diagram
Figure. 1
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SC4910A/B
POWER MANAGEMENT
Applications Information
The SC4910A/B is a secondary side PWM controller working either in current mode or voltage mode mainly for
applications of forward converters with synchronous rectification. While the OUTA drives the primary MOSFET
through transformer and the secondary forward rectifier, the OUTB drives the secondary freewheeling rectifier. The switching frequency and maximum duty cycle
can be programmable with two resistors. The delay time
from the falling edge of OUTA to the rising edge of OUTB
is adaptive by monitoring the phase node voltage. The
delay time from the falling edge of OUTB to the rising
edge of OUTA is determined by a programming resistor
from the DELAY pin to ground. The ISHARE pin allows for
current sharing among the parallel operating units to
make current equally distribute load. The -SENSE pin
separated from GND pin provides true output voltage
remote sense capability. Other features include soft start,
sychronization or enable/disable by user, provided 5V
reference voltage.
SYNC/EN
The enable function looks at the SYNC/EN pin and an
internal timing capacitor. If the SYNC/EN pin is low and
the internal timing capacitor voltage is high, then the
SC4910 is disabled with OUTA, OUTB and SS pulled low.
When the SYNC/EN pin is held high, the device is enabled
and runs off of the internal oscillator. When a rising signal
is detected on the SYNC/EN pin a one-shot is triggered
and discharges the internal timing capacitor. As long as
the internal timing capacitor is below an internal reference
level, the device will synchronize with the external pulse.
If the internal timing capacitor is allowed to charge up to
the internal reference level before another SYNC pulse
is detected, the device will switch back to the internal
oscillator.
Soft Start
The SS pin is connected to the internal reference, 0.75V,
through an internal 6K ohm resistor. The SS pin is also
connected to the non-inverting input of the error amplifier.
With an external capacitor connected to this pin, the soft
start timing will be determined by this RC time constant.
During start-up, the SS pin is held low until the
undervoltage lockout threshold is reached. Once the
UVLO threshold is reach, the SS pin is released and the
device will regulate to the voltage on this pin.
Oscillator
The frequency and duty cycle of the oscillator is controlled
by placing two resistors from the RT1 and RT2 pins to
ground. The resistor at RT1 controls the maximum “on”
duty cycle and the resistor at RT2 controls the “off”
portion of a cycle. When the resistor at RT1 is equal to
that at RT2, the maximum duty cycle will be approximately
50%. The following formula is used to determine the
time duration of the “on” and “off” portions:
t = RT × 20 × 10
Undervoltage Lockout
−12
When the supply voltage VCC is below the undervoltage
lockout threshold, both OUTA and OUTB are held low. The
SS pin and the COMP pin are also held low. Once the
undervoltage lockout threshold has been surpassed,
OUTA, OUTB, SS and COMP are released for normal
operation.
Current Sense and Current Limit
The CS pin has an input impedance of 20K ohms and
swings from 1.0V to 2.5V. With a 5K ohm resistor from
CS to ground, the device operates in voltage mode with
a ramp that will swing from 0.2V to 0.5V. When the 5K
resistor is connect to a voltage that is proportional to
the primary side current, the device will operate in current
mode. The cycle-by-cycle current limit is triggered when
the CS pin voltage rises above 1V. If CS exceeds 1.25V,
the faulty latch will be set and the outputs will be driven
low. The soft start capacitor is then discharged by the
internal current sink. No outputs are allowed until the
soft start capacitor is fully discharged to 0.15V. At this
point the fault latch will be reset and the SC4910 will
begin a soft start process. This results in a hiccup current
limit mode for continuous fault conditions.
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SC4910A/B
POWER MANAGEMENT
Applications Information (Cont.)
Programmable Delay
where
n – Power transformer primary to secondary turns ratio
NS – Secondary turns of current sense transformer
Io(pk) – Peak inductor current
SC4910 is for single ended topologies with secondary
side synchronous rectification. It provides outputs to drive
the primary MOSFET through a small pulse transformer
and the secondary synchronous rectifiers directly. To avoid
cross conduction and optimize performance, adjustable
delay is necessary between forwarding and freewheeling
switches. The delay from falling edge of OUTB to rising
edge of OUTA is determined by a resistor from the DELAY
pin to ground. The following formula is used to calculate
the delay time:
An example of choosing a current sense resistor is given
below. Assume the converter full load current is 20A and
peak inductor current is 23A, the power transformer
primary to secondary turns ratio is 6:1 and the current
sense transformer primary to secondary turns ratio is
1:100, then,
t DELAY = R • 1Ε − 12 + 20nS
Rs =
where, R is the delay time setting resistor.
R should be between 20K and 200K.
Slope Compensation
Slope compensation is needed to prevent sub-harmonic
oscillation at duty cycle higher than 50% and to
compensate the peak to average difference in peak
current mode control. The following equation can be used
to calculate the external slope. If negative Se is obtained
by the equation, no slope compensation is needed.
The delay time from falling edge of OUTA to rising edge of
OUTB is adaptive and is triggered when the PHASE node
falls below 1.5V. If after 220nS the PHASE node has still
not fallen, the device will automatically switch.
Operation Mode
SC4910 could be configured either current mode or
voltage mode operation. In current mode, the current
sense signal comes to the CS pin while an external resistor
could configure slope compensation. In voltage mode,
an external resistor forms sawtooth with the internal 20K
resistor for voltage mode operation while current limit
signal comes to the same pin.
In current mode, which is preferred for application of
SC4910, current is sensed by a current transformer for
current feedback and over current protection. The current
in the primary switch is sensed and controlled by
developing a voltage proportional to current across a
sense resistor on the secondary. The sensed voltage is
then fed into the CS pin of SC4910. The typical current
limit threshold in the current sense pin of the SC4910 is
1.0V. The over current limit is assumed typical 120% of
full load current. Then the current sense resistor can be
calculated by the following equation:
Rs =
 2005 Semtech Corp.
1.0 • 6 • 100
≈ 21Ω
120% • 23
Se ≥
2VOn − VIN VIN • ∆IL
RS
•
•
2( VIN − VOn)
VOn
n • NS
where
Se – External slope magnitude
Vin – Low input line voltage
Vo – Output voltage
n – Power transformer primary to secondary turns ratio
NS – Secondary turns of current sense transformer
∆IL - Peak-to-peak Inductor current ripple
For example, if the low input line voltage is 36V, output
voltage is 3.3V, power transformer primary to secondary
turns ratio is 6:1; the peak-to-peak inductor current ripple
is 6A, and current sense gain RS is 21W, then the external
slope needed is:
1.0 • n • NS
120 % • IO (pk )
Se ≥
9
2 • 3.3 • 6 − 36 36 • 6
21
•
•
≈ 85mV
2(36 − 3.3 • 6) 3.3 • 6 6 • 100
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SC4910A/B
POWER MANAGEMENT
Applications Information (Cont.)
Closed-Loop Compensation
This is the minimum external slope required to avoid subharmonic oscillation at low input line.
The simplified control-to-output transfer function for the
forward converter with current mode control, for small
value of external slope ( Se ≤ Sn, Sn is on-time slope of
sensed current waveform) is given by:
With SC4910, the external slope is very easy to
implement. Referring to Figure 2, R12 is the current sense
resistor. R10 and the internal 20KΩ resistor divide the
internal slope 1.0V - 2.5V down to the required
compensation slope.
G vg
where
where:
G vgo =
LM - Power transformer magnetizing inductance
fS = Switching frequency
In the example,
36 • 21
) • 20
450
E
−
6
• 100 • 250E3
R10 =
= 240Ω
36 • 21
(2.5 − 1.0) − (0.085 −
)
450E − 6 • 100 • 250E3
(0.085 −
5
C22
R25
12
PVCC
13
RT1
PHASE
U5
SC4910
RT2
OUTB
SS
COMP
FB
DELAY
VREF
C36
PGND
15
SY NC/EN
PGND
3
ISHARE
ωP =
1
Do min ant pole of power stage with current loop closed
RC
ωZ =
1
ESR zero of power stage
R ESR C
-SENSE
For the given example above, at low line and R = 0.165Ω,
C = 2 x 680uF = 1360uF, RESR = 17mΩ, therefore:
16
2
6
11
G vgo =
17
18
6 • 100 • 3.3
= 4.71 = 13dB
20 • 21
1
= 4456 rad / s = 710Hz
0.165 X 1360E − 6
1
ωZ =
= 43253 rad / s = 6887Hz
17E − 3 X 1360E − 6
ωP =
1
9
R22
OUTA
8
19
PVCC
14
20
AGND
R21
CS
7
4
10
AVCC
C13
nNS VO
DC gain of power stage with current loop closed
IOR S
where
R - Load resistance
C - Output capacitance
RESR - Output capacitors ESR
R10
R12
s
ωz
= G vgo
s
1+
ωp
1+
VIN • R S
) • 20
(Se −
L M • NS • fS
R10 =
VIN • R S
(2.5 − 1.0) − (Se −
)
L M • NS • f S
Figure 2
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SC4910A/B
POWER MANAGEMENT
Applications Information (Cont.)
The goal of the compensation design is to shape the loop
with high DC gain, high bandwidth, enough phase margin,
and high attenuation for high frequency noises. Figure 4
gives the asymptotic diagrams of the power stage with
current loop closed and its loop gain.
One integrator is added to increase the DC gain. Wzc is
used to cancel the power stage pole wp so that the loop
gain has –20dB rate when it reaches 0 dB line. wpc is
placed at output capacitor ESR or half switching frequency,
whichever is lower.
Arbitrarily choose R2, then
Type 2 compensator (Figure 3) is needed for the above
current mode control. The compensation network gives
the following characteristics:
C3
s
ω
ωz
= 1
s
s
1+
ωp
1+
C1
R1
-
GCOMP
R2
+
V ref
Figure 3
C1 =
1
R 2ωP
where
ω1 =
ωPC =
1
R 2 C1
Synchronization
1
CC
R2 1 3
C1 + C 3
Synchronization of oscillators in multiphase operation
allows for reduced size of filtering components and
improved dynamic response.
SC4910 provides single stage conversion where SC4201
provides the multiphase function. SC4910 and SC4201
are placed on the secondary side, outputs A and C of the
SC4201 are fed into the Sync pins of 2 separate
SC4910’s. Both power supplies operate 180 degrees
apart. SC4201 can be configured up to 4 phase
operation.
The loop gain will be given by:
s
s
1+
ω
V
ωz ω1
ZC
= G vgo
•
• ref
s
s
s
VO
1+
1+
ωp
ωPC
1+
T = G vg GCOMPK FB
C1
1
,R1 =
ωPC
ω
(
C
I
1 + C3 )
−1
ωZC
ωI is adjusted for satisfactory phase margin and
crossover frequency.
1
R 1 ( C1 + C 3 )
ω ZC =
, C3 =
Loop gain T(s)
ωzc
Compensator
Power stage
ωpc
fs
ωC
ωP
ωZ
Figure 4
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SC4910A/B
POWER MANAGEMENT
Applications Information (Cont.)
Load Remote Sensing
Load Current Sharing
Dedicated -SENSE pin provides true remote sensing of
the regulated supply’s output terminal voltage for high
current applications. As shown in Figure 5, the bandgap
reference “ground “ is brought out as –Sense, which is
connected to the “load ground” and to the local analog
ground by the resistor R10. With this way combined with
upper side R1, the voltage drop on power line is offset
and the load voltage is truly sensed.
A single wire connected between the ISHARE pins will
force current sharing between parallel units for paralleling
or n+1 redundant operation.
The ISHARE pin allows for current sharing between several
parallel units. The ISHARE pin connects internally to the
non-inverting input of ISHARE amplifier. An internal 4KΩ
resistor is between the inverting and non-inverting inputs
of this amplifier, with the inverting input also connected
to the COMP pin. The output of the amplifier connects
to the SS (0.75V ref) pin. During normal operation, when
all devices are sharing the load current equally, the COMP
pin voltages on each units should be approximately equal.
If one of the devices begins to take on too much or too
little of the load, the difference in COMP pin voltage will
cause the ISHARE amplifier to adjust the SS (0.75V ref)
voltage accordingly. In the event of ISHARE pulled down
below 1V, the ISHARE amplifier is disabled to prevent
output voltage of the unit lower than specification.
R1
15
14
AVCC
13
PVCC
RT1
OUTB
RT2
COMP
SS
FB
DELAY
SY NC/EN
VREF
-SENSE
7
AGND
5
PHASE
PGND
3
ISHARE
OUTA
PGND
19
SC4910
16
6
11
C5
17
C6
R7
R6
18
2
R8
1
R10
9
20
CS
8
4
10
PVCC
12
LOAD
Figure 5
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SC4910A/B
POWER MANAGEMENT
Typical Characteristics
Icc vs Temperature
Icc vs Vcc
25.00
20.00
16.00
Syn/En = High
Sync/En = High
Icc (mA)
Icc (mA)
Vcc = 12V
TA = 25°C
18.00
14.00
12.00
Sync/En = Low
10.00
15.00
Syn/En = Low
10.00
5.00
8.00
0.00
4.5
6.5
8.5
10.5
12.5
14.5
-40
-20
0
Vcc (V)
60
80
100
120
(Sc4910A) UVLO High Threshold vs Temperature
8.98
UVLO High Thre shold (V)
580.00
UVLO Hysteresis (mV)
40
Temperature (°C)
(Sc4910A) UVLO Hysteresis vs Temperature
575.00
570.00
565.00
560.00
555.00
550.00
8.97
8.96
8.95
8.94
8.93
8.92
8.91
8.90
-40
-20
0
20
40
60
80
100
120
-40
-20
0
Temperature (°C)
20
40
60
80
100
120
Temperature (°C)
(Sc4910B) UVLO Hysteresis vs Temperature
(Sc4910B) UVLO High Threshold vs Temperature
302.00
4.56
300.00
4.55
UVLO High Thre shold (V)
UVLO Hyste resis (mV)
20
298.00
296.00
294.00
292.00
290.00
288.00
286.00
284.00
4.55
4.54
4.54
4.53
4.53
4.52
4.52
-40
-20
0
20
40
60
80
100
120
-40
Temperature (°C)
 2005 Semtech Corp.
-20
0
20
40
60
80
100
120
Temperature (°C)
13
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SC4910A/B
POWER MANAGEMENT
Typical Characteristics (Cont.)
Bandgap Voltage vs Vcc
0.7505
TA = 25°C
Iout = 0mA
0.753
Vcc = 12V
Bandgap Voltage (V)
Bandgap Voltage (V)
0.755
Bandgap Voltage vs Temperature
0.751
0.749
0.747
0.745
0.7500
0.7495
0.7490
0.7485
0.7480
0.7475
9
10
11
12
13
14
15
-40
-20
0
20
Vcc (V)
140.00
TA = 25°C
Vfb = 5V
100.00
80.00
60.00
40.00
20.00
Vfb = 0V
0.00
4.5
6.5
8.5
10.5
12.5
600.00
Vcc = 12V
200.00
Vfb = 5V
100.00
0.00
Vfb = 0V
-100.00
-200.00
-40
-20
0
20
10.5
Error Amp Offset Voltage (mV)
60
80
100
120
Error Amp Offset Voltage vs Temperature
12.5
14.5
1.50
Vcc = 12V
1.40
1.30
1.20
1.10
1.00
0.90
0.80
-40
Vcc (V)
 2005 Semtech Corp.
40
Temperature (°C)
Error Amp Offset Voltage (mV)
8.5
120
300.00
14.5
TA = 25°C
6.5
100
400.00
Error Amp Offset Voltage vs Vcc
4.5
80
500.00
Vcc (V)
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
-0.20
-0.40
-0.60
60
Error Amp Input Bias Current vs Temperature
Error Amp Input Bias Curre nt
(nA)
Error Amp Input Bias Curre nt
(nA)
Error Amp Input Bias Current vs Vcc
120.00
40
Temperature (°C)
-20
0
20
40
60
80
100
120
Temperature (°C)
14
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SC4910A/B
POWER MANAGEMENT
Typical Characteristics (Cont.)
Oscillator Frequency vs Temperature
3.00
Oscillator Frequency (kHz)
Error Amp Output Voltage (V)
Error Amp Output Voltage vs Temperature
Vcc = 12V
Icomp = 1mA
2.50
2.00
High
1.50
1.00
Low
0.50
-40
-20
0
20
40
60
80
100
120
525
520
515
510
505
500
495
490
485
480
475
Rt1 = Rt2 = 50kohm
-40
-20
0
20
Temperature (°C)
Enable Voltage vs Temperature
Vcc = 12V
2.50
High
2.00
1.50
Low
1.00
0.50
-40
-20
0
20
40
60
60
80
100
120
Max Duty Cycle vs Temperature
Max Duty Cycle (%)
Enable Voltage (V)
3.00
40
Temperature (°C)
80
100
120
91.00
90.80
90.60
90.40
90.20
90.00
89.80
89.60
89.40
89.20
89.00
Output A
-40
Temperature (°C)
-20
0
20
40
60
80
100
120
Temperature (°C)
Progammable Delay vs Temperature
Progammable De lay (nS)
90.00
Rdelay = 50kohm
85.00
80.00
75.00
70.00
65.00
60.00
-40
-20
0
20
40
60
80
100
120
Temperature (°C)
 2005 Semtech Corp.
15
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Vin-
C3
1u,100V
C4
1u,100V
C5
1u,100V
C33
1u,100V
C34
1u,100V
M5
si4490dy
R53
8
Q3
FMMT718
D9
1N4148WS
D3
1N4148WS
0
C18
0.1uF
Q4
Not Populated
R17 1K
3
T3
C19
0.1uF
6 PE68386 1
4
1
3
7
R37
5.1
8
7
6
5
R12
22
R10
1.5K
R33
100K
R31
470K
C37
470pF
C28
100pF
R5 4.7
R35
20K
C30
47nF
4
3
COMP
FB
R30
100K
R28
2.7MEG
0.1uF
C22
R22 75K
R25
62K
R27
100K
f s=250KHz
R36
100K
4
7
C16
0.1uF
ILIM
OUT
5
7
M4
si4842dy
10
R51
U5
SC4910
C31
1000pF
51
R32
C29
150pF
R29
68
4
3
1
2
8
5
R34
1.00
16
2
1
18
17
11
6
R26
10.0
D15
SMAZ20
R38
10K
R18
10K
C21
C24
47uF
C25
47uF
+12V
43K
R23
C20
100pF
1.0nF
D12 1N4148WS
Q1
Si2320DS
PB2090
T4
-SENSE
FB
COMP
OUTB
PHASE
SY NC/EN
ISHARE
C17
0.1uF
+12V
R4 10K
C11
0.1uF
+12V
4
2
D10
1N4148WS
C23
47uF
C27
10uF
0.1uF
C36
VREF
DELAY
SS
RT2
RT1
OUTA
CS
R8
4.7
5
U2
SC1302A
Q2
FMMT718
U6 SC4911
5
15
3
19
20
10
D21*
1N5819HW
R21 124K
D11 1N4148WS
C12
0.1uF
+12V
C13
150pF
R3
5.1
C1
2.2nF
D5
1N4148WS
D14
B130L
D22*
1N5819HW
Q5
FMMT718
R6 10K
Ilim=24A
+12PRI
4
2
R11
10K
D6
1N4148WS
D2
1N4148WS
M2si4842dy
1
2
3
4
M1 si4842dy
8
1
7
2
6
3
5
4
C32
2.2nF
C26
0.47uF
+Vin
5
U4
SC1302A
10
D20*
1N5819HW
R50
8
10
M6
si4490dy
P8208T
7 T2
2
5
5
6
7
8
4
3
2
1
ES1D
D1
C2
0.1uF,100V
5
6
7
8
4
3
2
1
M7
Not populated
R1
39K
5
6
7
8
4
3
2
1
M3
si4842dy
8
Vin+
8
8
7
6
5
1
2
3
4
1
6
3
T1
1
6
3
14
AVCC
AGND
7
PA0168A
8
VCC
GND
1
LUVLO
RT
2
16
6
8
7
6
5
1
2
3
4
12
PVCC
13
PVCC
PGND
8
PGND
9
R52
1K
C50
22nF
C51
10uF
L1
1.3uH
R13
10.0K
5
C14
0.1uF
+12V
C7
100uF
R24
2.0K
R19
6.8K
U3
SC4431
C6
100uF
1
+Vin
C8
680uF
V re f
 2005 Semtech Corp.
2
CON1
4
R15
18.2K
R14
37.4K
C9
680uF
* : Optional
R2
10.0
7
6
5
4
3
1
Vout-
EN
Ishare
Sense
Sense
Vout+
CON2
3.3V/20A
SC4910A/B
POWER MANAGEMENT
Evaluation Board Schematics
www.semtech.com
SC4910A/B
POWER MANAGEMENT
Evaluation Board Bill of Materials
Item
Quantity Reference
3
2
C1,C32
4
1
C2
5
5
6
Part
Manufacturer #
2.2nF
Foot Print
SM/C_0805
0.1uF,100V
TDK, C3216X7R2A104M
SM/C_1206
C3,C4,C5,C33,C34
1uF,100V
Murata,
GRM55RR72A105KA01B
SM/C_2220
4
C6,C7,C8,C9
680uF, 4V
Sanyo, 4TPB680
SM/CT_7343
7
10
C11,C12,C14,C16,C17,C18,C19,
C22,C36, C51
0.1uF
SM/C_0805
8
2
C13,C29
150pF
SM/C_0805
9
1
C 20
560pF
SM/C_0805
10
1
C 21
1.5nF
SM/C_0805
11
3
C23,C24,C25
12
1
C 26
0.47uF
13
1
C 27
10uF, 10V
14
1
C 28
100pF
SM/C_0805
15
1
C 30
47nF
SM/C_0805
16
1
C 31
1000pF
SM/C_0805
17
1
C 37
470pF
SM/C_0805
18
1
C 50
22nF
SM/C_0805
19
1
D1
E S 1D
20
10
21
1
D 14
B 130L
22
1
D 15
23
1
L1
24
4
M1,M2,M3,M4
25
2
26
D2,D5,D6,D9,
D10,D11,D12,D20,D21,D22
47uF, 16V
Sanyo, 16TPB47
SM/CT_7343
SM/C_1206
Murata,
GRM32ER61C106KC31L
Diodes Inc. ES1D-13
1N5819HW Diodes Inc. 1N5819HW-7
SM/C_1210
SM/_SMA
SOD123
Diodes Inc. B130L-13
SMA
SMAJ20A
Diodes Inc. SMAJ120A-13
SMA
1.3uH
Panasonic, ETQPAF1R3E
PCC-S1
si 4 8 4 2 d y
Vishay
SO-8
M5,M6
si 4 4 9 0 d y
Vishay
SO-8
1
Q1
S i 2320D S
Vishay
SM/SOT23_123
27
1
R1
39K
SM/R_0805
28
2
R2,R26
10
SM/R_0805
29
2
R3,R37
5.1
SM/R_0805
30
6
R4,R6,R11,R17,R18,R38
10K
SM/R_0805
31
2
R5, R8
4.7
SM/R_0805
 2005 Semtech Corp.
17
www.semtech.com
SC4910A/B
POWER MANAGEMENT
Evaluation Board Bill of Materials
Item
Quantity Reference
Part
Manufacturer #
Foot Print
32
1
R10
412
SM/R_0805
33
1
R12
22
SM/R_0805
34
1
R13
10.0K
SM/R_0805
35
1
R14
37.4K
SM/R_0805
36
1
R15
18.2K
SM/R_0805
37
1
R19
21.5K
SM/R_0805
38
1
R21
160K
SM/R_0805
39
1
R22
40.2K
SM/R_0805
40
1
R23
43K
SM/R_0805
41
1
R24
6.19K
SM/R_0805
42
1
R25
110K
SM/R_0805
43
3
R27,R30,R33
100K
SM/R_0805
44
1
R28
2.7MEG
SM/R_0805
45
3
R29
68
SM/R_0805
46
1
R31
383K
SM/R_0805
47
1
R32
51
SM/R_0805
48
1
R34
1
SM/R_0805
49
1
R35
4.7K
SM/R_0805
50
1
R36
130K
SM/R_0805
51
2
R50,R51
10
SM/R_0805
52
1
R52
1.0K
SM/R_0805
53
1
T1
PA0168
Pulse
XP4
54
1
T2
P 8208T
Pulse
P 8208
55
1
T3
P E 68386
Pulse
P E 68386
56
1
T4
31414R
Midcom
57
2
U2, U4
S C 1302A
Semtech
SOT23_5PIN
58
1
U3
S C 4431
Semtech
SOT23_5PIN
59
1
U5
S C 4910
Semtech
TSSOP-20
60
1
U6
SC4911
Semtech
MSOP-8
 2005 Semtech Corp.
18
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SC4910A/B
POWER MANAGEMENT
Outline Drawing - TSSOP-20
A
D
e
2X E/2
E
PIN 1
INDICATOR
ccc C 1 2 3
2X N/2 TIPS
e/2
B
1.20
0.15
0.05
1.05
0.80
0.19
0.30
0.20
0.09
6.40 6.50 6.60
4.30 4.40 4.50
6.40 BSC
0.65 BSC
0.45 0.60 0.75
(1.0)
20
0°
8°
0.10
0.10
0.20
D
aaa C
SEATING
PLANE
.047
.006
.002
.042
.031
.007
.012
.007
.003
.251 .255 .259
.169 .173 .177
.252 BSC
.026 BSC
.018 .024 .030
(.039)
20
8°
0°
.004
.004
.008
A
A1
A2
b
c
D
E1
E
e
L
L1
N
01
aaa
bbb
ccc
N
E1
DIMENSIONS
MILLIMETERS
INCHES
MIN NOM MAX MIN NOM MAX
DIM
A2 A
C
H
A1
bxN
bbb
C A-B D
c
GAGE
PLANE
0.25
SIDE VIEW
SEE DETAIL
L
(L1)
DETAIL
A
01
A
NOTES:
1.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. DATUMS -A-
AND -B-
TO BE DETERMINED AT DATUM PLANE-H-
3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
OR GATE BURRS.
4. REFERENCE JEDEC STD MO-153, VARIATION AC.
Land Pattern - TSSOP-20
F
DIM
(C)
H
G
C
F
G
H
P
X
Y
Z
Z
Y
P
NOTES:
1.
DIMENSIONS
INCHES
MILLIMETERS
(.222)
.157
.161
.126
.026
.016
.061
.283
(5.65)
4.00
4.10
3.20
0.65
0.40
1.55
7.20
X
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
Contact Information
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804
 2005 Semtech Corp.
19
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