POWER MANAGEMENT
1www.semtech.com
SC1110
Sink and Source DC/DC Controller for
Termination Power Supply Applications
Features
Applications
Revision: July 20, 2004
Typical Application Circuit
Description
The SC1110 is a low-cost, full featured, synchronous
voltage-mode controller designed to generate
termination voltage in double data rate (DDR) memory
systems and other applications where wide data bus
need to be actively terminated. Synchronous control of
the MOSFET half bridge allows power flowing
bi-directionally. The termination voltage can be tightly
regulated to track the chipset voltage, i.e. to be exactly
50% of that at all times.
The SC1110 is ideal for low cost implementation of
termination voltage supplies. SC1110 features include
temperature compensated voltage reference, triangle
wave oscillator and current sense comparator circuitry,
and allows the use of inexpensive N-channel power
MOSFETs.
The SC1110 operates at a fixed 250kHz, providing an
optimum compromise between efficiency, transient
performance, external component size, and cost.
Generates termination voltages for active termina-
tion schemes
1% set point accuracy
For ±7A output current, transient regulation is
better than ±80mV
VREFIN pin available for external 50% resistive divider
to allow termination voltage track of the chip set
voltage
Buffered VREFOUT for system usage
RDSON sensing for over current protection in hiccup
mode
Soft start and logic input enabling
250kHz switching for best transient and efficiency
performance
Gate drive capable for 0.5A sourcing and sinking
For DDR memory systems
For active termination schemes in high speed logic
systems
Q1
Si9426DY
Q2
Si9426DY
R8
2.2
R3
10
L1
800 nH
D1
MBRM120
C6
1.0
C12-14
3 x 560uF
C10,11
2 x 560uF
R6
4.7k
C2
0.1
C4
0.022
C1
0.01 R2
1.24k
REFOUT
SS/ENBL
+
_
+
_
Vin 2.5V
Vout = 1.25V @ 7A
+5Vcc
R7
2.2
C8,9
2 x 10uF
C7
1.0
C5
0.047
C15-24
10 x 10uF
C10-14: Sanyo, 4SP560M
C8,9,15-24: TDK, CC3216AX5R0J106K
Q1,Q2 options: Si9426DY, FDS6890A, IRF7401
D1: ON Semi
(
Motorola
)
L1: Panasonic, ETQP6F0R8L or Falco, QPIP1205-809-3
R4
1k
R5
1k
C3
0.1
VCC
1REFOUT 14
SS/ENBL
2
OCSET
3
GND
5
PHASE
6
DL
7DH 8
BSTH 9
BSTL 10
COMP 11
SENSE 12
REFIN 13
PWRGD
4
U1
SC1110
PWRGD
R1
5k
C25
0.1
2 2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Electrical Characteristics
Absolute Maximum Ratings
retemaraPlobmySmumixaMstinU
V
CC
DNGotLTSB,V
NI
41ot5.0-V
DNGotDNGP +5.0V
DNGotESAHP 81ot3.0-V
ESAHPotHTSB 41V
esaCotnoitcnuJecnadepmIlamrehT θ
CJ
54W/C°
tneibmAotnoitcnuJecnatsiseRlamrehT θ
AJ
511W/C°
egnaRerutarepmeTgnitarepOT
A
07ot0C°
egnaRerutarepmeTegarotST
GTS
051+ot56-C°
.ceS01)gniredloS(erutarepmeTdaeLT
DAEL
003C°
)ledoMydoBnamuH(gnitaRDSEV
DSE
2Vk
Unless specified: VCC = 4.75V to 12.6V; GND = PGND = 0V; FB = VO; VBSTL = 12V; VBSTH-PHASE = 12V; TJ = 25oC
retemaraPsnoitidnoCniMpyTxaMstinU
ylppuSrewoP
egatloVylppuSV
CC
4.46.21V
tnerruCylppuS 821Am
noitalugeReniLV
O
V,V5.0±V5.2=
O
V=
NI
A0@2/5.0%
tuokcoLegatloVrednU
dlohserhTnO-nruT 51.4V
dlohserhTffO-nruT 59.3V
reifilpmArorrE
ecnatcudnocsnarT 2Sm
niaGCDpooLnepO 05Bd
Bd3-htdiwdnaB)zHM07revossorcniagytinU(005zHk
ytilibapaCecruoSPMOC 052±Aµ
saiBtupnI 25Aµ
rotallicsO
ycneuqerFrotallicsO 522052572zHk
elcyCytuDxaMrotallicsO 0959%
thgieHpmaR 1V
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.
3
2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
retemaraPsnoitidnoCniMpyTxaMstinU
gnimiT
emiT-ffOmuminiM 002sn
emiTdaeDnoitaziretcarahcybdeetnarauG08sn
srevirDTEFSOM
tnerruCecruoS/kniSHDkaeP V0.3=ESAHP-HD,V5.4=HD-HTSB
V5.1=ESAHP-HD
5.0A
1.0
tnerruCecruoS/kniSLDkaeP V0.3=DNG-LD,V5.4=LD-LTSB
V5.1=DNG-LD
5.0A
1.0
noitcetorP
ecruosIteStnerrucrevOV
TESCO
V2.2=081002022Aµ
tratStfoS
tnerruCegrahCV
SS
V5.1=80121Aµ
tnerruCegrahcsiDV
SS
V5.1=123Aµ
dooGrewoP
dlohserhTreppU 211%
dlohserhTrewoL 88%
woLegatloVDGRWPI
DGRWP
Am2=5.0V
ecnerefeR
tnerruCecruoSTUOFER 3Am
tesffOFER
NI
V52.1=5-5Vm
elbanE
dlohserhT 55.006.056.0V
Electrical Characteristics (Cont.)
Unless specified: VCC = 4.75V to 12.6V; GND = PGND = 0V; FB = VO; VBSTL = 12V; VBSTH-PHASE = 12V; TJ = 25oC
4 2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Timing Diagrams
SIMULASIMULA
SIMULASIMULA
SIMULATION WTION W
TION WTION W
TION WAA
AA
AVEFVEF
VEFVEF
VEFORMSORMS
ORMSORMS
ORMS
Output current of the VTT supply
2.5V and 1.25V ramp up
5
2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Pin Configuration Ordering Information
Pin Descriptions
eciveD
)1(
egakcaP
)2()1(
T(egnaRpmeT
J
)
TRTSC0111CS41-OSC°521ot°0
TRTST0111CS41-POSST
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(2) Lead free product.
#niPemaNniPnoitcnuFniP
1CCV.egatloVylppuSpihC
2LBNE/SS.elbanE/tratstfoS
3TESCO.tnioptestimiltnerruC
4DGRWP.tuptuotcerrocsetacidnihgihcigoL
5DNG.dnuorG
6ESAHP.sTEFSOMneewtebnoitcennocedonesahP
7LD.tuptuorevirdediswoL
8HD.tuptuorevirdedishgiH
9HTSB.ylppusrevirdedishgiH
01LTSB.ylppusrevirdediswoL
11PMOC.noitasnepmoc,tuptuoreifilpmarorrE
21ESNES.tupnievitagenreifilpmarorrE
31NIFER.tupnievitisopreifilpmarorrE
41TUOFER.egatlovecnereferdereffuB
NOTE:NOTE:
NOTE:NOTE:
NOTE:
(1) All logic level inputs and outputs are open collector TTL compatible.
(14 Pin SOIC or TSSOP)
6 2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Block Diagram
Applications Information
THEORY OF OPERATION
Synchronous Buck Converter
VTERMINATION power is provided by a synchronous, voltage-
mode pulse width modulated (PWM) controller. This sec-
tion has all the features required to build a high efficiency
synchronous buck converter for termination of power
application.
The output voltage of the synchronous converter is set
and controlled by the output of the error amplifier. The
external resistive divider generates reference voltage for
the error amplifier from the chipset voltage which is
usually 2.5V. The inverting input of the error amplifier
receives its voltage from the SENSE pin.
The internal oscillator uses an on-chip capacitor and
trimmed precision current sources to set the oscillation
frequency to 250kHz. The triangular output of the oscil-
lator sets the reference voltage at the inverting input of
the PWM comparator. The non-inverting input of the com-
parator receives it’s input voltage from the error ampli-
fier. When the oscillator output voltage drops below the
error amplifier output voltage, the comparator output
goes high. This pulls DL low, turning off the low-side FET,
and DH is pulled high, turning on the high-side FET (once
the cross-current control allows it). When the oscillator
voltage rises back above the error amplifier output volt-
age, the comparator output goes low. This pulls DH low,
turning off the high-side FET, and DL is pulled high, turn-
ing on the low-side FET (once the cross-current control
allows it).
As SENSE increases, the output voltage of the error
amplifier decreases. This causes a reduction in the on-
time of the high-side MOSFET connected to DH, hence
lowering the output voltage.
Under Voltage Lockout
The under voltage lockout circuit of the SC1110 assures
that both the high-side MOSFET driver outputs remain in
the off state whenever the supply voltage drops below
set parameters. Lockout occurs if VCC falls below 4.1V.
Normal operation resumes once VCC rises above 4.2V.
7
2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Soft Start
Initially, SS/ENABLE sources 10µA of current to charge
an external capacitor. The outputs of the error amplifiers
are clamped to a voltage proportional to the voltage on
SS/ENABLE. This limits the on-time of the high-side
MOSFETs, thus leading to a controlled ramp-up of the
output voltages.
RDS(ON) Current Limiting
The current limit threshold is set by connecting an exter-
nal resistor from the VCC supply to OCSET. The voltage
drop across this resistor is due to the 200µA internal
sink sets the voltage at the pin. This voltage is compared
to the voltage at the PHASE node. This comparison is
made only when the high-side drive is high to avoid false
current limit triggering due to uncontributing measure-
ments from the MOSFET’s off-voltage. When the voltage
at PHASE is less than the voltage at OCSET, an overcurrent
condition occurs and the soft start cycle is initiated. The
Applications Information
synchronous switcher turns off and SS/ENABLE starts
to sink 2µA. When SS/ENABLE reaches 0.8V, it then
starts to source 10µA and a new cycle begins.
Hiccup Mode
During power up, the SS/ENABLE pin is internally pulled
low until VCC reaches the undervoltage lockout level of
4.2V. Once VCC has reached 4.2V, the SS/ENABLE pin is
released and begins to source 10µA of current to the
external soft-start capacitor. As the soft-start voltage
rises, the output of the internal error amplifier is clamped
to this voltage. When the error signal reaches the level
of the internal triangular oscillator, which swings from 1V
to 2V at a fixed frequency of 250 kHz, switching occurs.
As the error signal crosses over the oscillator signal, the
duty cycle of the PWM signal continues to increase until
the output comes into regulation. If an over-current con-
dition has not occurred the soft-start voltage will con-
tinue to rise and level off at about 2.2V.
8 2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Typical Characteristics
CH1: Vout_ripple
CH2: Phase node
Vin = 2.5V
Vout = 1.25V
Iout = 7A
60%
65%
70%
75%
80%
85%
90%
95%
0123456789101112
Current, A
Efficiency
-1.0%
-0.5%
0.0%
0.5%
1.0%
0123456789101112
Current, A
Regulation
9
2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Evaluation Board
Top View
Bottom View
10 2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Evaluation Board (Cont.)
Top Copper Bottom Copper
Midlayer 1 Midlayer 2
11
2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
Land Pattern - SO-14
Outline Drawing - SO-14
12 2004 Semtech Corp. www.semtech.com
POWER MANAGEMENT
SC1110
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-14
Outline Drawing - TSSOP-14
