1 www.semtech.com
SC4910A/B
High Performance Secondary Side
Controller with Synchronous Rectifier
POWER MANAGEMENT
Revision: June 1, 2005
Description Features
Applications
Typical Application Circuit
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 is an integrated, full featured, second-
ary 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 rectifica-
tion. 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 synchro-
nous rectification.
The SC4910A/B features synchronous rectification, multi-
phase link capability, programmable secondary side
delay, programmable switching frequency and program-
mable maximum duty cycle. It is designed for either
current mode or voltage mode operation.
The SC4910A has a typical turn-on threshold of 9V and
the SC4910B has a threshold of 4.5V.
+12V
C4
LOAD
C6
T3
R3
C5
C1
M1
SC1301
M2
R8
C10
R4
R7
T2
C2
R2
R6
L1
D2
SC4910
18
17
11
12
6
4
87
20
19
3
1
15 2
5
10
FB
COMP
OUTB
ISHARE
PHASE
CS
OUTA
PGND
RT1
RT2
SS
-SENSE
DELAY SYNC/EN
VREF
PVCC
M3
SC1301
D3
C8
+Vin
R1
C9
SC1301
R9
C3
D1
R5
T1
16
13 14
PVCC AVCC
9
PGNDAGND
Telecom isolated DC to DC converters
Isolated VRMS
Networking power supplies
Industrial power supplies
Distributed power architectures
High density power modules
2 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Absolute Maximum Ratings
Electrical Characteristics
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tnerruCgnitarepOwoL=NE/CNYS0151Am
tuokcoLegatlovrednU
dlohserhTtratS
A0194CS7.80.93.9V
B0194CS53.405.457.4V
siseretsyHOLVU
A0194CS004055007Vm
B0194CS002003573Vm
ecnerefeRFERV
egatloVtuptuO
A0194CS57.40.552.5V
B0194CS79.203.336.3V
noitalugeReniLV51<ccV<V3.95103Vm
noitalugeRdaoLI<Am0
FER
Am5<201Vm
tratStfoS
tuptuOSS 57.0V
ycaruccAegatloV
T
A
T=
J
C°52=1-1+
%
5.1-5.1+
noitalugeReniLV51<ccV<V3.95-05+Vm
ecnadepmI
)2(
K7 Ω
retemaraPlobmySmumixaMstinU
egatloVylppuSccV81V
egatloVtuptuO ccVV
esahP ccVV
ERAHSI,NE/CNYS,PMOC,BF 7ot3.0-V
kniSroecruoStnerruCBTUO&ATUO 051Am
egnaRerutarepmeTnoitcnuJT
J
051+ot04-C°
egnaRerutarepmeTegarotST
GTS
051+ot06-C°
.ceS01)gniredloS(erutarepmeTdaeLT
DAEL
062C°
Unless specified: TA = T
J
= -40°C to 125°C , VCC = 12V, R
T1
= R
T2
= 50K, R
DELAY
= 50K, C
SS
= 0.1µF.
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.
3 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Electrical Characteristics (Cont.)
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reifilpmArorrE
tnerruCsaiBtupnI 1.05Aµ
egatloVtesffO 27 Vm
niaGpooLnepO 08 Bd
RRMC
)1(
07 Bd
RRSP
)1(
07 Bd
egatloVhgiHtuptuO I
PMOC
Am0.1=57.19.1 V
egatloVwoLtuptuO I
PMOC
Am0.1=9.00.1 V
htdiwdnaBniaGytinU
)1(
0.5 zHM
etaRwelS
)1(
0.2 Sµ/V
rotallicsO
egnaRycneuqerFRycneuqerF.niM
1T
R=
2T
K005=05zHK
RycneuqerF.xaM
1T
R=
2T
K52=0001
ycneuqerF 054005055zHK
egatloVkaeP
)1(
5.2V
egatloVyellaV
)1(
0.1 V
hgiHtupnIelbanE 0.2 V
woLtupnIelbanE 8.0 V
elcyCytuD
elcyCytuDmumixaM
)2(
09 %
elcyCytuDmuminiM 0%
ecnareloTelcyCytuD 5-5+%
timiLtnerruC
dlohserhTelcyCybelcyC 579.0520.1570.1 V
dlohserhTnwodtuhS 1.152.14.1 V
tuptuOotyaleD
)2(
001 Sn
ecnadepmItupnI
)2(
02 kΩ
Unless specified: TA = T
J
= -40°C to 125°C , VCC = 12V, R
T1
= R
T2
= 50K, R
DELAY
= 50K, C
SS
= 0.1µF.
4 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
retemaraPsnoitidnoCtseTniMpyTxaMtinU
BTUOdnaATUO
woLtuptuO I
TUPTUO
Am001=13.1 V
hgiHtuptuO I
TUPTUO
Am001=57.901V
emiTesiR
)2(
C
TUO
Fp001=02Sn
emiTllaF
)2(
C
TUO
Fp001=02Sn
yaleD
gnisiRATUOotgnillaFBTUO
)2(
R
YALED
K05= Ω07 Sn
gnisiRBTUOotgnillaFATUO
)2(
V5.1>ESAHP022 Sn
V5.1<ESAHP03
reifilpmArorrEerahStnerruC
ecnatcudnocsnarT
)1(
81.0 Sm
tnerruCkniSroecruoStuptuO
)1(
01 Aµ
Electrical Characteristics (Cont.)
Notes:
(1) Guaranteed by design.
(2) Guaranteed by characterization.
(3) This device is ESD sensitive. Use of standard ESD handling requirements are required.
Unless specified: TA = T
J
= -40°C to 125°C , VCC = 12V, R
T1
= R
T2
= 50K, R
DELAY
= 50K, C
SS
= 0.1µF.
5 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
rebmuNtraPegakcaP
TRTSTIA0194CS
)2(
02-POSST
)1(
TRTSTIB0194CS
)2(
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.
Pin Configurations Ordering Information
1
2
3
4
5
6
7
8
RT1-SENSE
TOP VIEW
(20 Pin TSSOP)
13
14
15
16
RT2SYNC/EN
FBSS
COMPCS
ISHAREVREF
DELAYPHASE
AVCCAGND
PVCCPGND
9
10
12 PVCCPGND
OUTBOUTA 11
18
17
19
20
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)
6 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Pin Descriptions
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4SC.tupniesnestnerruC
5FERV.tuptuoecnereferlanretniV5
6ESAHP.noitacifitcersuonorhcnysrofedonesahP
7DNGA.dnuorggolanA
8DNGP.ATUOrofdnuorgrewoP
9DNGP.BTUOrofdnuorgrewoP
01ATUO .OLVUgnirudwoL.TEFSOMdrawrofyradnocesdnaTEFSOMyramirprofrevirdtuptuO
11BTUO .OLVUgnirudwoL.reifitcerdrawrofroflangisgnivirdTEFSOMehttuptuO
21CCVP.BTUOrofylppusrewoP
31CCVP.ATUOrofylppusrewoP
41CCVA.egatlovylppusgolanA
51YALED gnileehweerfehtfoffo-nrutmorfsiyaledehT.BTUOdnaATUOneewtebyaledevitciderP
ot02siemityaledehT.TEFSOMyramirpdnaTEFSOMdrawrofehtfono-nrutotTEFSOM
.elbammargorpSn002
61ERAHSI.suberahstnerruC
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81BF.kcabdeeF
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021TR .rotallicsolanretniehtfopmarevitisopehtlortnocot1TRrotsisergnimitottcennoC
7 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Block Diagram
Figure. 1
8 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Applications Information
The SC4910A/B is a secondary side PWM controller work-
ing either in current mode or voltage mode mainly for
applications of forward converters with synchronous rec-
tification. While the OUTA drives the primary MOSFET
through transformer and the secondary forward recti-
fier, the OUTB drives the secondary freewheeling recti-
fier. 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.
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:
12
1020 −
××= RTt
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.
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.
Undervoltage Lockout
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.
9 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Programmable Delay
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:
nS20121RtDELAY +−Ε•=
where, R is the delay time setting resistor.
R should be between 20K and 200K.
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:
)pk(I%120
Nn0.1
Rs
O
S
•••
=
Applications Information (Cont.)
where
n – Power transformer primary to secondary turns ratio
NS – Secondary turns of current sense transformer
Io(pk) – Peak inductor current
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,
Ω≈
•
••
=21
23%120
10060.1
Rs
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.
S
S
O
LIN
OIN
INO
Nn
R
nV
IV
)nVV(2
VnV2
Se •
•
ƥ
•
−−
≥
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:
mV85
1006
21
63.3
636
)63.336(2
3663.32
Se ≈
•
•
•
•
•
•− −••
≥
10 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
This is the minimum external slope required to avoid sub-
harmonic oscillation at low input line.
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.
)
fNL
RV
Se()0.15.2(
20)
fNL
RV
Se(
10R
SSM
SIN
SSM
SIN
•• •
−−−
•
•• •
−
=
where:
LM - Power transformer magnetizing inductance
fS = Switching frequency
In the example,
Ω=
••− •
−−−
•
••− •
−
=240
)
3E2501006E450
2136
085.0()0.15.2(
20)
3E2501006E450
2136
085.0(
10R
R10
C36
R22
C22
C13
U5
SC4910
18
17
11
16
6
4
10
7
20
19
3
1
15
2
5
14
8
9
13
12
FB
COMP
OUTB
ISHARE
PHASE
CS
OUTA
AGND
RT1
RT2
SS
-SENSE
DELAY
SY NC/EN
VREF
AVCC
PGND
PGND
PVCC
PVCC
R21
R12
R25
Figure 2
Applications Information (Cont.)
Closed-Loop Compensation
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:
p
z
vgovg s
1
s
1
GG
ω
+
ω
+
=
where
closedloopcurrentwithstagepowerofgainDC
RI
VnN
G
SO
OS
vgo =
closedloopcurrentwithstagepowerofpoleantminDo
RC
1
P=ω
stagepowerofzeroESR
CR
1
ESR
Z=ω
where
R - Load resistance
C - Output capacitance
RESR - Output capacitors ESR
For the given example above, at low line and R = 0.165Ω,
C = 2 x 680uF = 1360uF, RESR = 17mΩ, therefore:
dB1371.4
2120
3.31006
Gvgo ==
•••
=
Hz6887s/rad43253
6E1360X3E17
1
Hz710s/rad4456
6E1360X165.0
1
Z
P
==
−−
=ω
==
−
=ω
11 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Type 2 compensator (Figure 3) is needed for the above
current mode control. The compensation network gives
the following characteristics:
p
z1
COMP s
1
s
1
s
G
ω
+
ω
+
ω
=
Figure 3
where
31
31
2
PC
12
ZC
311
1
CC
CC
R
1
CR
1
)CC(R
1
+
=ω
=ω
+
=ω
The loop gain will be given by:
O
ref
PC
ZC
1
p
z
vgoFBCOMPvg V
V
s
1
s
1
s
s
1
s
1
GKGGT •
ω
+
ω
+
ω
•
ω
+
ω
+
==
Figure 4
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
)CC(
1
R,
1
C
C,
R
C
31I
1
ZC
PC
1
3
P2
1
1+ω
=
−
ω
ω
=
ω
=
ωI
is adjusted for satisfactory phase margin and
crossover frequency.
Synchronization
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.
R2
C3
C1
R1
Vref
-
+
ωC
ωpc
ωZ
ωP
Loop gain T(s)
Power stage
Compensator
ωzc
fs
12 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Load Remote Sensing
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.
R7
R8
LOAD
R10
C5
SC4910
18
17
11
16
6
4
10
7
20
19
3
1
15 2
5
12
8
9
13
14
FB
COMP
OUTB
ISHARE
PHASE
CS
OUTA
AGND
RT1
RT2
SS
-SENSE
DELAY SYNC/EN
VREF
PVCC
PGND
PGND
PVCC
AVCC
C6
R1
R6
Figure 5
Load Current Sharing
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.
Applications Information (Cont.)
13 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Typical Characteristics
Icc vs Vcc
8.00
10.00
12.00
14.00
16.00
18.00
4.5 6.5 8.5 10.5 12.5 14.5
Vcc (V)
Icc (mA)
TA = 25°C
Sync/En = High
Sync/En = Low
Icc vs Temperature
0.00
5.00
10.00
15.00
20.00
25.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Icc (mA)
Vcc = 12V
Syn/En = High
Syn/En = Low
(Sc4910A) UVLO Hysteresis vs Temperature
550.00
555.00
560.00
565.00
570.00
575.00
580.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
UVLO Hysteresis (mV)
(Sc4910A) UVLO High Threshold vs Temperature
8.90
8.91
8.92
8.93
8.94
8.95
8.96
8.97
8.98
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
UVLO High Thre shold (V)
(Sc4910B) UVLO Hysteresis vs Temperature
284.00
286.00
288.00
290.00
292.00
294.00
296.00
298.00
300.00
302.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
UVLO Hysteresis (mV)
(Sc4910B) UVLO High Threshold vs Temperature
4.52
4.52
4.53
4.53
4.54
4.54
4.55
4.55
4.56
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
UVLO High Thre shold (V)
14 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Typical Characteristics (Cont.)
Error Amp Input Bias Current vs Vcc
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
4.5 6.5 8.5 10.5 12.5 14.5
Vcc (V)
Error Amp Input Bias Current
(nA)
TA
= 25°C
Vfb = 5V
Vfb = 0V
Error Amp Input Bias Current vs Temperature
-200.00
-100.00
0.00
100.00
200.00
300.00
400.00
500.00
600.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Error Amp Input Bias Current
(nA)
Vcc = 12V
Vfb = 5V
Vfb = 0V
Error Amp Offset Voltage vs Vcc
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
4.5 6.5 8.5 10.5 12.5 14.5
Vcc (V)
Error Amp Offset Voltage (mV)
TA = 25°C
Error Amp Offset Voltage vs Temperature
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Error Amp Offset Voltage (mV)
Vcc = 12V
Bandgap Voltage vs Vcc
0.745
0.747
0.749
0.751
0.753
0.755
9 101112131415
Vcc (V)
Bandgap Voltage (V)
TA = 25°C
Iout = 0mA
Bandgap Voltage vs Temperature
0.7475
0.7480
0.7485
0.7490
0.7495
0.7500
0.7505
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Bandgap Voltage (V)
Vcc = 12V
15 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Error Amp Output Voltage vs Temperature
0.50
1.00
1.50
2.00
2.50
3.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Error Amp Output Voltage (V)
Vcc = 12V
Icomp = 1mA
High
Low
Oscillator Frequency vs Temperature
475
480
485
490
495
500
505
510
515
520
525
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Oscillator Frequency (kHz)
Rt1 = Rt2 = 50kohm
Enable Voltage vs Temperature
0.50
1.00
1.50
2.00
2.50
3.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Enable Voltage (V)
Vcc = 12V
High
Low
Max Duty Cycle vs Temperature
89.00
89.20
89.40
89.60
89.80
90.00
90.20
90.40
90.60
90.80
91.00
-40 -20 0 20 40 60 80 100 120
Te mpe rature (°C)
Max Duty Cycle (%)
Output A
Progammable Delay vs Temperature
60.00
65.00
70.00
75.00
80.00
85.00
90.00
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Progammable Delay (nS)
Rdelay = 50kohm
Typical Characteristics (Cont.)
16 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Evaluation Board Schematics
D5
1N4148WS
Q2
FMMT718
D6
1N4148WS
C1
2.2nF
+12V
R3
5.1
27
63
1
8
45
U4
SC1302A
D1
ES1D
+12PRI
+Vin
C17
0.1uF
FB 18
COMP 17
OUTB 11
ISHARE 16
PHASE 6
CS
4
OUTA
10
AGND
7
RT1
20
RT2
19
SS
3
-SENSE 1
DELAY
15
SYNC/EN 2
VREF
5
AVCC 14
PGND
8
PGND
9
PVCC 13
PVCC 12
U5
SC4910
1
34
6
T3
PE68386
D10
1N4148WS
R14
37.4K
R15
18.2K
R25
62K
D12 1N4148WS
R12
22
R11
10K
R37
5.1
Ilim=24A
3.3V/20A
R27
100K
D11 1N4148WS
R1
39K
+Vin
C11
0.1uF
D15
SMAZ20
4 5
3
2
1
6
7
8
M6
si4490dy
4 5
3
2
1
6
7
8
M7
Not po pulat ed
C16
0.1uF
C32
2.2nF
C12
0.1uF
C26
0.47uF
1u,100V
C33
1u,100V
C34
4 5
3
2
1
6
7
8
M3
si4842dy
R26
10.0
45
3
2
1
6
7
8
M2si4842dy R18
10K
R38
10K
fs=250KHz
R13
10.0K
Vin+
Vin-
CON1
C18
0.1uF
C28
100pF
C19
0.1uF
C13
150pF
R5 4.7
C22
0.1uF
LUVLO 1
RT
2
FB
3
COMP
4ILIM 5
GND
6
OUT 7
VCC 8
U6 SC4911
R6 10K
C20
100pF
C21
1.0nF
R50
10
8
7
1
3
T2
P8208T
3
4
5
8
2
1
T4
PB2090
2
5
8
10
T1
PA0168A
D14
B130L
C23
47uF
R8
4.7
R4 10K
C30
47nF
C24
47uF
C31
1000pF
C29
150pF
C2
0.1uF,100V
C36
0.1uF
C25
47uF
L1
1.3uH
C8
680uF
+12V
* : Optional
R28
2.7MEG
R30
100K
R35
20K
R31
470K
12
4
5
Vref
U3
SC4431
R33
100K
R36
100K
R34
1.00
R29
68
R32
51
Q3
FMMT718
Q4
Not Populated
+12V
C14
0.1uF
C37
470pF
Q1
Si2320DS
D9
1N4148WS
D20*
1N5819HW
C50
22nF
1u,100V
C5
R17 1K
D22*
1N5819HW
D21*
1N5819HW
Q5
FMMT718
D2
1N4148WS
C27
10uF
R51
10
1u,100V
C4
1u,100V
C3
+12V
45
3
2
1
6
7
8
M1 s i4 84 2d y
4 5
3
2
1
6
7
8
M4
si4842dy
+12V
D3
1N4148WS
27
63
1
8
45
U2
SC1302A
R53
0
R21 124K
Vout -
7
Sens
e
4
Ishar
e
5
Sens
e
3
Vout +
1
EN
6
CON2
C6
100uF
R22 75K R23
43K
R10
1.5K
4 5
3
2
1
6
7
8
M5
si4490dy
R52
1K
C51
10uF
C7
100uF
R24
2.0K
R19
6.8K
C9
680uF
R2
10.0
17 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
metIytitnauQecnerefeRtraP#rerutcafunaMtnirPtooF
32 23C,1CFn2.25080_C/MS
412CV001,Fu1.0M401A2R7X6123C,KDT6021_C/MS
55 43C,33C,5C,4C,3CV001,Fu1,ataruM
B10AK501A27RR55MRG
0222_C/MS
64 9C,8C,7C,6CV4,Fu086086BPT4,oynaS3437_TC/MS
701,91C,81C,71C,61C,41C,21C,11C
15C,63C,22C
Fu1.05080_C/MS
82 92C,31CFp0515080_C/MS
91 02CFp0655080_C/MS
01112CFn5.15080_C/MS
113 52C,42C,32CV61,Fu7474BPT61,oynaS3437_TC/MS
21162CFu74.06021_C/MS
31172CV01,Fu01,ataruM
L13CK601C16RE23MRG
0121_C/MS
41182CFp0015080_C/MS
51103CFn745080_C/MS
61113CFp00015080_C/MS
71173CFp0745080_C/MS
81105CFn225080_C/MS
9111DD1SE31-D1SE.cnIsedoiDAMS_/MS
0201,9D,6D,5D,2D
22D,12D,02D,21D,11D,01D
WH9185N17-WH9185N1.cnIsedoiD321DOS
12141DL031B31-L031B.cnIsedoiDAMS
22151DA02JAMS31-A021JAMS.cnIsedoiDAMS
3211LHu3.1E3R1FAPQTE,cinosanaP1S-CCP
424 4M,3M,2M,1Myd2484isyahsiV8-OS
522 6M,5Myd0944isyahsiV8-OS
6211QSD0232iSyahsiV321_32TOS/MS
7211RK935080_R/MS
822 62R,2R015080_R/MS
922 73R,3R1.55080_R/MS
036 83R,81R,71R,11R,6R,4RK015080_R/MS
132 8R,5R7.45080_R/MS
Evaluation Board Bill of Materials
18 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Evaluation Board Bill of Materials
metIytitnauQecnerefeRtraP#rerutcafunaMtnirPtooF
23101R2145080_R/MS
33121R225080_R/MS
43131RK0.015080_R/MS
53141RK4.735080_R/MS
63151RK2.815080_R/MS
73191RK5.125080_R/MS
83112RK0615080_R/MS
93122RK2.045080_R/MS
04132RK345080_R/MS
14142RK91.65080_R/MS
24152RK0115080_R/MS
343 33R,03R,72RK0015080_R/MS
44182RGEM7.25080_R/MS
54392R865080_R/MS
64113RK3835080_R/MS
74123R155080_R/MS
84143R15080_R/MS
94153RK7.45080_R/MS
05163RK0315080_R/MS
152 15R,05R015080_R/MS
25125RK0.15080_R/MS
3511T8610APesluP4PX
4512TT8028PesluP8028P
5513T68386EPesluP68386EP
6514TR41413mocdiM
752 4U,2UA2031CShcetmeSNIP5_32TOS
8513U1344CShcetmeSNIP5_32TOS
9515U0194CShcetmeS02-POSST
0616U1194CShcetmeS8-POSM
19 2005 Semtech Corp. www.semtech.com
SC4910A/B
POWER MANAGEMENT
Outline Drawing - TSSOP-20
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804
Contact Information
Land Pattern - TSSOP-20
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
NOTES:
1.
F
X
H
INCHES
DIMENSIONS
Z
P
Y
X
DIM
C
G
MILLIMETERS
H .126 3.20
F .157 4.00
(.222) (5.65)
ZG
Y
P
(C)
4.10.161
0.65.026
0.40.016
1.55.061
7.20.283
L
(L1)
c
01
GAGE
PLANE
SEE DETAIL DETAIL A
A
0.25
.026 BSC
.252 BSC
20
.004
.169
.251
.173
.255
.007 -
20
0.10
0.65 BSC
6.40 BSC
4.40
6.50
-
.177
.259
4.30
6.40
.012 0.19
4.50
6.60
0.30
bxN
2X N/2 TIPS
SEATING
aaa C
E/2
INDICATOR
PIN 1
2X
1 32
N
E1
bbb C A-B D
ccc C
DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS3.
OR GATE BURRS.
DATUMS AND TO BE DETERMINED AT DATUM PLANE
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
-B-
NOTES:
1.
2. -A- -H-
SIDE VIEW
(.039)
.004
.008
-
.024
-
-
-
-
0°
.018
.003
.031
.002
-
8° 0°
0.20
0.10
-8°
0.45
0.09
0.80
0.05
.030
.007
.047
.042
.006
-
(1.0)
0.60
-
0.75
0.20
-
-
-1.20
1.05
0.15
A
B
C
D
e
e/2
H
PLANE
D
E
A1
A2 A
REFERENCE JEDEC STD MO-153, VARIATION AC.
4.
INCHES
b
N
ccc
aaa
bbb
01
E1
E
L
L1
e
D
c
A2
A1
DIM
A
MIN MAX
MILLIMETERS
MIN
DIMENSIONS
NOM MAX NOM
