1www.semtech.com
SC250
Step-Down DC-DC Converter with
Bias LDO for RF Power Amplifi ers
POWER MANAGEMENT
August 28, 2006
Typical Application Circuit
Applications
The SC250 is a synchronous step-down converter
designed specifi cally for use as an adaptive voltage
supply for CDMA and WCDMA RF Power Amplifi ers (PAs).
The output voltage can be adjusted dynamically between
0.3V and (Vin - 0.4)V through a linear analog control input.
For high power operation, a maximum control input signal
level forces the device into bypass mode where the input
is connected directly to the output via an internal P-
Channel pass transistor. Bypass mode also occurs when
the output load demands duty cycles in excess of the
maximum rated duty cycle.
The SC250 also provides an LDO regulator which can be
used to supply a 2.85V bias to the PA. The internal clock
runs at 1MHz to maximize effi ciency while still allowing
the use of small surface mount inductors and capacitors
can be used.
The peak current rating of the internal PMOS switch allows
a DC output current of 600mA. The bypass PMOS current
rating allows a minimum of 1A DC output current in the
bypass mode. Shutdown turns off all the control circuitry
to achieve a typical shutdown current of 0.1A.
CDMA and WCDMA Phones
Handheld Radios
RF PC Cards
Battery Powered RF Devices
Adjustable output voltage range — 0.3 to 3.6V
Linearly proportional VDAC to VOUT relationship for
increased PA effi ciency
Pass-through mode automatic and on demand
Input voltage range — 2.7V to 5V
Typical settling time — 40s
Output current capability — 600mA
Maximum output current in bypass mode — 1A
Up to 96% effi ciency
Constant frequency operation — 1MHz
Less than 1A shutdown current
Internal 75m PMOS bypass transistor
PA bias voltage supply — 2.85V, 20mA, 1.5%
MLPD-W8, 2.3 x 2.3mm package
L1
4.7H
CIN
10F
VIN
VOUT
VREF
GND
LX
VDAC
PGND CREF
1F
EN
COUT
4.7μF
VIN
3
6
1
4
2
7
5
8
PA
RF Output
RF Input
Vcc
GNDBIAS
ENABLE
VDAC
SC250
Description Features
2
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SC250
PRELIMINARY
POWER MANAGEMENT
Electrical Characteristics
Unless otherwise noted: VIN = VEN =3.6V, TA = -40 to 85°C. Typical values are at TA = +25°C.
Parameter Symbol Conditions Min Typ Max Units
Input Voltage Range VIN 2.7 5.0 V
VOUT Accuracy VOUT
VIN = 4V, VDAC = 0.1V, IOUT = 0.3A 0.25 0.3 0.35 V
VIN = 4V, VDAC = 1.1V, IOUT = 0.3A 3.23 3.3 3.37 V
VOUT Line Regulation VOUT LINE VIN = 2.7V to 5.0V, VDAC = 0.7V 0.4 %/V
VOUT Load Regulation VOUT LOAD IOUT = 0A to 600 mA, VDAC = 0.7V -0.7 %
VREF Accuracy VREF IREF = 10 mA 2.8 2.85 2.9 V
VREF Line Regulation VREF LINE IREF = 1 mA, IOUT = 0A 0.3 %/V
VREF Load Regulation VREF LOAD IREF = 0.1 to 20 mA -0.5 %
VREF Load Current IREF 20 mA
Peak Inductor Current ILX PK 0.8 1.5 A
Bypass FET Current Limit IPASS 1 2.5 A
Exceeding the specifi cations below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specifi ed in the
Electrical Characteristics section is not recommended.
Parameter Symbol Maximum Units
Input Supply Voltage VIN -0.3 to 7 V
EN and VDAC Inputs VEN, VDAC -0.3 to 7 V
LX Pin Voltage (Power switch OFF) VLX -1 to VIN + 1, 7V MAX V
VOUT Voltage VOUT -0.3 to 7 V
VOUT Short Circuit to GND duration tSC Continuous s
Thermal Impedance Junction to Ambient (1) JA 110 °C/W
Operating Ambient Temperature Range TA-40 to +85 °C
Junction Temperature TJC +150 °C
Storage Temperature TS-60 to +160 °C
Peak IR Refl ow Temperature TP260 °C
ESD Protection Level (2) VESD 2kV
Absolute Maximum Ratings
Note:
1) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
2) Tested according to JEDEC standard JESD22-A114-B.
3
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SC250
PRELIMINARY
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Parameter Symbol Conditions Min Typ Max Units
Quiescent Current IQ
Normal Mode (VDAC < 1V) 1.5
mA
Bypass Mode (VDAC > 1.4V) 1
Shutdown Current ISD
LX = open, EN = GND, VOUT = open,
TA= 25°C 0.1 1 A
VDAC Regulated Output
Mode VDAC VIN = 4.2V 0.10 1.20 V
VDAC Pass-Through
Mode Threshold VDAC PT
VDAC Rising 1.28 1.37
V
VDAC Falling 1.20 1.3
VDAC to VOUT Transfer
Ratio GV3 V/V
RDS ON of Bypass
P-Channel FET RPASS IOUT = 100mA, VIN = 3V, VDAC= 1.4V 75 m
RDS ON of P-Channel
Switching FET RDSP IOUT = 100mA, VIN = 3V 400 m
RDS ON of N-Channel
Switching FET RDSN IOUT = 100mA, VIN = 3V 250 m
LX Leakage Current PMOS ILXP VIN = 3.6V, LX = 0V, EN = GND 2 A
LX Leakage Current NMOS ILXN VIN = 3.6V, LX = 3.6V, EN = GND 2 A
VOUT Pin Bypass
PMOS Leakage ILVOUT VIN = 3.6V, VOUT = 0V, EN = GND 2 A
Oscillator Frequency
(Fixed Frequency) fOSC VDAC > 0.2V 0.85 1 1.15 MHz
Oscillator Frequency
(Variable Frequency) fOSCV VDAC = 0.1V 0.65 MHz
Logic Input High VIH 1.6 V
Logic Input Low VIL 0.6 V
Control Input Current - High IIH VDAC/EN =3.6V ±2 A
Control Input Current - Low IIL VDAC/EN = GND ±2 A
Enable Transient
Over/Undershoot OSEN 20 %
Enable Transient Settling
Time tEN-ST 40 s
VDAC Transient
Over/Undershoot OSVDAC 20 %
VDAC Transient Settling
Time tVDAC-ST 40 s
4
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SC250
PRELIMINARY
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Parameter Symbol Conditions Min Typ Max Units
Pass-Through Transition
Over/Undershoot OSPASS 20 %
Pass-Through Transition
Settling Time tPASS-ST 40 s
Thermal Shutdown TSD 160 °C
Thermal Shutdown
Hysteresis TSDH 15 °C
Auto Pass-Through
Threshold (VIN-VOUT)PTTH 400 430 460 mV
Auto Pass-Through
Threshold Hysteresis PTTH_HYST 135 160 190 mV
5
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SC250
PRELIMINARY
POWER MANAGEMENT
Pin Confi guration
Ordering Information
Note:
1) Available on tape and reel only. A reel contains 3000 devices.
2) Device is WEEE and RoHS compliant.
DEVICE PACKAGE
SC250WLTRT(1)(2) MLPD-W8 2.3x2.3
SC250EVB Evaluation Board
Ordering Information
Marking Information
TOP VIEW
MLPD-W8 2.3 x 2.3
1
2
45
63
7
8PGND
EN
VOUT
VDAC
LX
VIN
VREF
GND
Marking for the 2.3 x 2.3mm MLPD 8 Lead Package:
ww = Datecode (Reference Package Marking Design
Guidelines, Appendix A)
250
yw
6
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SC250
PRELIMINARY
POWER MANAGEMENT
Block Diagram
Control Logic
6
References
VIN
VREF
EN
GND
VDAC
PGND
LX
VOUT
SENSE
SENSE
Error Amp.
PWM
Comparator
Oscillator Slope Generator
Current
Sense
12
8
3
4
7
5
7
© 2006 Semtech Corp. www.semtech.com
SC250
PRELIMINARY
POWER MANAGEMENT
Pin Descriptions
Pin # Pin Name Pin Function
1LXInductor connection to the switching FETs
2 VIN Input voltage connection
3 VREF 2.85V, 20mA reference supply — can be used as a supply for power amplifi er bias inputs or
to supply a resistive divider on VDAC to set a fi xed level of VOUT.
4 GND Ground connection
5 VDAC
Analog control voltage input ranges between 0.1 and 1.2V for control of VOUT in accordance
with the VOUT= 3 x VDAC transfer function. VDAC > 1.4V enables pass-through mode using
the internal pass MOSFET.
6 VOUT Regulated output voltage and feedback
7EN
Enable digital input: a high input enables the SC250, a low disables the output and
reduces quiescent current to less than 1A and LX becomes high impedance.
8 PGND Ground reference for internal N-channel MOSFET
8
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SC250
PRELIMINARY
POWER MANAGEMENT
Applications Information
SC250 Detailed Description
The SC250 adaptive power controller is a step-down,
fi xed frequency pulse-width modulated DC-DC converter
designed for use with RF Power Amplifi ers (PAs) in
CDMA and WCDMA handsets and modules. The SC250
output is used to supply DC power to the PA rather than
connecting the DC input pin directly to the battery supply.
A substantial system power effi ciency improvement can
be achieved by allowing the system controller to adaptively
adjust the DC power to the PA, reducing the total power
consumption of the device when in low-power mode. To
improve effi ciency at all RF output gain settings, the PA
supply voltage is adjusted in a linear fashion, minimizing
PA supply headroom and losses.
A consequence of using the SC250 to power the PA, rather
than using a linear regulator or direct connection to the
battery, is that less current is needed. Reduced current
consumption results in more talk-time for the handset.
Operation Modes
The SC250 output voltage is dependent on the VDAC analog
control voltage, defi ned by the following relationship:
V
OUT = 3 × VDAC
In a typical PA system application, the system controller
determines what output power level is needed from the
PA and adjusts the VDAC voltage to match the required PA
headroom for optimized effi ciency.
Pass-Through Mode
When the VDAC voltage reaches 1.36V, the SC250
enters pass-through mode. If the demanded output
voltage is within 430mV of the input voltage, the SC250
automatically enters pass-through as this exceeds the
maximum controlled duty cycle of the power converter.
In pass-through mode, the device enables an internal P-
Channel MOSFET that bypasses the converter, connecting
the output directly to the input. The RDSON of this FET is
extremely low, so there is little voltage drop across the part.
Pass-through allows the lowest insertion loss possible
between VIN and VOUT under high-power conditions, thereby
maintaining maximum effi ciency under these conditions.
Bias Supply Output
In addition to the main output, the SC250 also provides a
low current LDO output that can be used as a bias supply
for power amplifi ers. This output provides a regulated
2.85V with output current capability up to 20mA. The
2.85V output is guaranteed for input supply voltages in
excess of 2.95V.
Protection Features
The SC250 provides the following protection features:
Thermal shutdown
Current limit
Under-voltage lockout
Thermal Shutdown
The device has a thermal shutdown feature to protect the
device if the junction temperature exceeds 150°C. In
thermal shutdown, the PWM drive is disabled, effectively
tri-stating the LX output. The device will not be enabled
again until the temperature reduces by 10°C.
Short-Circuit Protection
The PMOS and NMOS power devices of the buck switcher
stage are protected by current limit functions. In the case
of a short to ground on the output, the LX pin will switch
with minimum duty cycle. The duty cycle is short enough to
allow the inductor to discharge during each cycle, thereby
preventing the inductor current from “staircasing.”
The pass-through PMOS is also protected by a current
limit function. When the part is fi rst enabled in pass-
through, the output capacitor charges up with a large
surge current. This surge current is internally limited for
protection purposes, but the limit is set high enough to
meet fast start-up times. In order to protect against a
short-circuit condition and to allow the transient response
time, an internal timer allows the part to operate under
current limit conditions for a maximum of 64 cycles of the
internal clock (1MHz typical). If the short-circuit conditions
persists, the pass-through PMOS will turn off for 1ms,
after which the fi rst timer is restarted. This allows the part
to manage thermal dissipation while giving it the ability to
recover when the fault condition is removed.
•
•
•
9
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SC250
PRELIMINARY
POWER MANAGEMENT
Under-Voltage Lockout
Under-voltage lockout protection is used to prevent
erroneous operation. As the input decreases, the device
shuts down when the voltage drops below 2.35V and will
not restart until the input voltage exceeds approximately
2.5V.
Inductor Selection
The SC250 is designed for use with a 4.7H inductor. The
magnitude of the inductor current ripple is dependent on
the inductor value and can be determined by the following
equation:
OSC
N I
OUT
OUT
L
f
L
V
V
1V
Iu
¸
¹
·
¨
©
§
'
This equation demonstrates the relationship between
input voltage, output voltage, and inductor ripple current.
The inductor should have a low DC resistance to minimize
the conduction losses and maximize effi ciency. As a
minimum requirement, the DC current rating of the
inductor should be equal to the maximum load current
plus half of the inductor current ripple as shown by the
following equation:
2
I
II L
)MAX(OUTLPK
'
Final inductor selection depends on various design
considerations such as effi ciency, EMI, size, and cost.
Table 1 lists the manufacturers of practical inductor
options.
Table 1 — Recommended Inductors
Manufacturer/Part # Value
(H)
DCR
()
Saturation
Current (A)
Tolerance
(%)
Dimensions
LxWxH (mm)
BI Technologies
HM66304R7 4.7 0.072 1.32 20 4.7 × 4.7 ×3.0
Coilcraft
D01608C-472ML 4.7 0.09 1.5 20 6.6 × 4.5 ×3.0
TDK
VLCF4018T- 4R7N1R0-2 4.7 0.101 1.07 30 4.3 × 4.0 ×1.8
CIN Selection
The source input current to a buck converter is non-
continuous. To prevent large input voltage ripple, a low
Applications Information (Cont.)
ESR ceramic capacitor is required. A minimum value of
10F should be used for suffi cient input voltage fi ltering
and a 22F should be used for improved input voltage
fi ltering.
COUT Selection
The internal compensation is designed to work with a
certain output fi lter corner frequency defi ned by the
equation:
OUT
CCL2
1
fuS
This single pole fi lter is designed to operate with an output
capacitor value of 4.7F.
Output voltage ripple is a combination of the voltage
ripple from the inductor current charging and discharging
the output capacitor, and the voltage created from the
inductor current ripple through the output capacitor ESR.
Selecting an output capacitor with a low ESR will reduce
the output voltage ripple component that is dependent
upon this ESR, as can be seen in the following equation:
)COUT()ripple(L)ESR(OUT ESRIV u' '
Capacitors with X7R or X5R ceramic dielectric are
strongly recommended for their low ESR and superior
temperature and voltage characteristics. Y5V capacitors
should not be used as their temperature coeffi cients
make them unsuitable for this application. Table 2 lists
the manufacturers of recommended capacitor options.
Table 2 — Recommended Capacitors
Manufacturer/Part Number Value
(F)
Rated
Voltage
(VDC)
Type Case Size
Murata
GRM21BR60J226ME39L 22 6.3 X5R 0805
Murata
GRM188R60J106MKE19 10 6.3 X5R 0603
TDK
C2012X5R0J106K 10 6.3 X5R 0603
Murata
GRM188R60J475KE19D 4.7 6.3 X5R 0603
10
© 2006 Semtech Corp. www.semtech.com
SC250
PRELIMINARY
POWER MANAGEMENT
Applications Information (Cont.)
PCB Layout Considerations
Poor layout can degrade the performance of the DC-
DC converter and can be a contributory factor in EMI
problems, ground bounce and resistive voltage losses.
Poor regulation and instability can result.
A few simple design rules can be implemented to ensure
good layout:
Place the inductor and fi lter capacitors as close to the
device as possible and use short wide traces between
the power components.
Route the output voltage feedback and VDAC path away
from inductor and LX node to minimize noise and
magnetic interference.
1.
2.
Maximize ground metal on component side to improve
the return connection and thermal dissipation.
Separation between the LX node and GND should be
maintained to avoid coupling of switching noise to the
ground plane.
To further reduce noise interference on sensitive
circuit nodes, use a ground plane with several vias
connecting to the component side ground.
3.
4.
LX L
OUT
C
OUT
SC250
V
OUT
VREF
GND
C
REF
V
IN
C
IN
VDAC
EN
PGND
1
11
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SC250
PRELIMINARY
POWER MANAGEMENT
Typical Characteristics
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1
I
OUT
(V)
Efficiency (%)
V
IN
=3.6V
V
IN
=3.9V
V
IN
=4.2V
Effi ciency vs. Load Current VOUT = 3.2V
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1
Efficiency (%)
I
OUT
(V)
VIN=3.9V
VIN=4.2V
VIN=3.3V
Effi ciency vs. Load Current VOUT = 2.5V
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1
Efficiency (%)
I
OUT
(V)
V
IN
=4.2V
V
IN
=2.7V
V
IN
=3.6V
Effi ciency vs. Load Current VOUT = 1.5V
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1
Efficiency (%)
I
OUT
(V)
V
IN
=4.2V
V
IN
=2.7V
V
IN
=3.6V
Effi ciency vs. Load Current VOUT = 1.2V
0
10
20
30
40
50
60
70
80
90
100
2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Efficiency (%)
V
IN
(V)
IOUT=10mA
IOUT=600mAIOUT=300mA IOUT=100mA
Effi ciency vs. VIN
0
10
20
30
40
50
60
70
80
90
100
00.511.522.533.5
Efficiency(%)
V
IN
(V)
IOUT=100mA
IOUT=600mA
Effi ciency vs. VOUT, VIN = 3.6V
12
© 2006 Semtech Corp. www.semtech.com
SC250
PRELIMINARY
POWER MANAGEMENT
Typical Characteristics (Cont.)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
`
VDAC (V)
VIN=5.5V
VOUT (V)
VIN=4.2V
VIN=3.6V
VIN=3.0V
VIN=2.7V
Control Transfer Function IOUT = 0.3A
2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
V
IN
(V)
V
OUT
(V)
V
IN
Up
V
IN
Down
Auto Bypass Function, VOUT = 3.25V
0
0.001
0.002
0.003
0.004
0.005
0.006
2.5 3 3.5 4 4.5 5 5.5 6
V
OUT
=2.1V
VIN (V)
IIN (A)
V
OUT
=1.5V
V
OUT
=0.3V
Dynamic Supply Current vs. VIN
T
J
(°C)
I
Q
Shutdown (A)
0
2
4
6
8
10
12
14
16
-40 -20 0 20 40 60 80 100 120
Shutdown Current vs. Temperature, VIN = 3.6V
2
2.05
2.1
2.15
2.2
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
I
OUT
(A)
V
OUT
(V)
Load Regulation, VOUT = 2.1V
1.49
1.495
1.5
1.505
1.51
1.515
1.52
2.533.54 4.555.56
V
OUT
(V)
50mA
150mA
300mA
600mA
T
A
(°C)
Line Regulation, VOUT = 1.5V
13
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SC250
PRELIMINARY
POWER MANAGEMENT
Typical Characteristics (Cont.)
1.46
1.48
1.5
1.52
1.54
1.56
-60 -40 -20 0 20 40 60 80 100
V
OUT
(V)
T
A
(°C)
I
OUT
=10mA I
OUT
=600mA
I
OUT
=300mA
I
OUT
=100mA
VOUT vs. Temperature (VOUT = 1.5V)
3.16
3.18
3.2
3.22
3.24
3.26
-60 -40 -20 0 20 40 60 80 100
V
OUT
(V)
T
A
(°C)
I
OUT
=10mA
I
OUT
=600mA
I
OUT
=300mAI
OUT
=100mA
VOUT vs. Temperature (VOUT = 3.2V)
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
V
IN
(V)
V
REF
(V)
VREF vs. VIN
2.835
2.84
2.845
2.85
2.855
2.86
2.865
0 0.005 0.01 0.015 0.02 0.025
I
REF
(A)
V
REF
(V)
VREF vs. IREF
0
0.5
1
1.5
2
2.5
3
1 1.1 1.2 1.3 1.4 1.5 1.6
I
OUT
(A)
VIN=5.0V
V
OUT
(V)
VIN=4.5V VIN=3.5V
VIN=4.0V
Maximum Output Current, VOUT = 2.5V
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1 1.1 1.2 1.3 1.4 1.5 1.6
I
OUT
(A)
V
IN
=5.0V
V
OUT
(V)
V
IN
=4.5V
V
IN
=3.5V
V
IN
=4.0V
Maximum Output Current, VOUT = 1.8V
14
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SC250
PRELIMINARY
POWER MANAGEMENT
Typical Characteristics (Cont.)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1 1.1 1.2 1.3 1.4 1.5 1.6
I
OUT
(A)
V
IN
=5.0V
V
OUT
(V)
V
IN
=3.5V
V
IN
=3.0V
V
IN
=2.7V
V
IN
=4.0V
V
IN
=4.5V
Maximum Output Current, VOUT = 1.5V
0
5
10
15
20
25
30
35
40
45
50
0 0.10.20.30.40.50.60.7
Dropout Voltage (mV)
IOUT (A)
Dropout Voltage vs. Bypass Load Current
1120
1140
1160
1180
1200
1220
1240
1260
1280
-40 -20 0 20 40 60 80 100 120
PMOS Current Limit (mA)
T
J
(°C)
PMOS Current Limit vs. Temperature
1400
1450
1500
1550
1600
1650
1700
-40 -20 0 20 40 60 80 100 120
Passthrough Current Limit (mA)
T
J
(°C)
Passthrough Current Limit vs. Temperature
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Switching Frequency (kHz)
V
DAC
(V)
Oscillator Frequency vs. VDAC, VIN = 3.6V
940
960
980
1000
1020
1040
1060
1080
-40 -20 0 20 40 60 80 100 120 140
Oscillator Frequency (kHz)
T
J
(°C)
Oscillator Frequency vs. Temperature, VIN = 3.6V
15
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SC250
PRELIMINARY
POWER MANAGEMENT
VDAC Step Response (100% duty)
VDAC Step Response
VDAC Step Response (Pass-through)
Typical Characteristics (Cont.)
Time (40s/div)
Condition VIN=3.6V, Load=15, VDAC=0.7 to 1.7V
VOUT (1V/div)
VDAC (1V/div)
VLX (2V/div)
VOUT (1V/div)
VDAC (500mV/div)
VLX (2V/div)
Time (40s/div)
Condition VIN=4.2V, Load=15, VDAC=0.5 to 1.1V
Time (40s/div)
Condition VIN=3V, Load=15, VDAC=0.7 to 1V
VOUT (1V/div)
VDAC (500mV/div)
VLX (2V/div)
Enable Transient
VOUT (1V/div)
VLX (2V/div)
VEN (2V/div)
Time (40s/div)
Condition VIN=3.6V, Load=15, VDAC=0.7V
0
50
100
150
200
250
300
350
400
450
-45 5 55 105 155
TJ(°C)
PASS
PMOS
NMOS
R
DSON
(m
Ω
)
RDSON vs. Temperature, VIN = 3.6V
0
50
100
150
200
250
300
350
400
2.5 3.0 3.5 4.0 4.5 5.0 5.5
V
IN
(V)
PMOS
NMOS
PASS
R
DSON
(mΩ)
RDSON vs. VIN
16
© 2006 Semtech Corp. www.semtech.com
SC250
PRELIMINARY
POWER MANAGEMENT
Typical Characteristics (Cont.)
Enable Start-Up
VEN (2V/div)
VOUT (1V/div)
VLX (5V/div)
IIN (500mA/div)
Time (20s/div)
Condition VIN=4.2V, Load=15, VOUT=3.4V
Output Ripple Waveform (VOUT=3.25V)
VOUT (50mV/div)
VLX(5V/div)
Time (1s/div)
Condition VIN=4.2V, Load=300mA, VOUT=3.25V
Pass-Through Current Limit
VOUT (1V/div)
VLX(2V/div)
Time (1ms/div)
Condition VIN=3.6V, Load=1, VDAC=1.4V
Output Ripple Waveform (VOUT=1.5V)
VOUT (50mV/div)
VLX(5V/div)
Time (1s/div)
Condition VIN=3.6V, Load=300mA, VOUT=1.5V
Load Step response (VOUT=3.25V)
VOUT (100mV/div)
IOUT(500mA/div)
Time (40s/div)
Condition VIN=4.2V, Load=600mA-60mA, VOUT=3.25V
Load Step response (VOUT=1.5V)
VOUT (100mV/div)
IOUT(500mA/div)
Time (40s/div)
Condition VIN=3.6V, Load=600mA-60mA, VOUT=1.5V
17
© 2006 Semtech Corp. www.semtech.com
SC250
PRELIMINARY
POWER MANAGEMENT
Outline Drawing - MLPD-W8, 2.3 x 2.3
Marking Information
18
© 2006 Semtech Corp. www.semtech.com
SC250
PRELIMINARY
POWER MANAGEMENT
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 FAX (805)498-3804
Contact Information
Land Pattern - MLPD-W8, 2.3 x 2.3
www.semtech.com
