SC185
POWER MANAGEMENT
Features
4A Synchronous
Step-Down Regulator
Description
The SC185 is a 4A synchronous step-down regulator
designed to operate with an input voltage range of
2.9V to 5.5V. The device requires only three external
filter components for a complete a step down regulator
solution. The output voltage is factory predetermined
with an available range of 1.0V to 3.3V.
The SC185 is optimized for maximum efficiency over a
wide range of load currents. During full load operation,
the SC185 operates in PWM mode with fixed 1.5MHz
oscillator frequency, allowing the use of small surface
mount external components. As the load decreases, the
regulator has the option to transition into Power Save
mode maintaining high efficiency or stay in forced PWM
mode operation.
The SC185 offers output short circuit and thermal
protection to safe guard the device under extreme
operating conditions. The enable pin provides on/off
control of the regulator. When connected to logic
low, the device enters shutdown and consumes less
than 1uA of current. Other protection features include
programmable soft start with Power Good indicator, over
voltage protection and under voltage lockout.
The SC185 is available in a thermally-enhanced, 3mm
x 3mm x 0.6mm MLPQ-UT16 package and has a rated
temperature range of -40 to +85°C.
V
IN
Range: 2.9 – 5.5V
V
OUT
Options: 1.0V to 3.3V
Up to 4A Output Current
Ultra-Small Footprint, <1mm Height Solution
1.5MHz Switching Frequency
Optional Power Save Mode Operation
Efficiency Up to 95%
Low Output Noise Across Load Range
Excellent Transient Response
Start Up into Pre-Bias Output
100% Duty-Cycle Low Dropout Operation
<1µA Shutdown Current
Externally Programmable Soft Start Time
Power Good indicator
Input Under-Voltage Lockout
Output Over-Voltage, Current Limit Protection
Over-Temperature Protection
3mm x 3mm x 0.6mm thermally enhanced
MLPQ-UT16 package
-40 to +85°C Temperature Range
Pb-free, Halogen free, and RoHS/WEEE compliant
Fixed VOUT version
Applications
Desktop Computing
Set-Top Box
LCD TV
Network Cards
Printer
Typical Application Circuit
V
IN
C
IN
22µF
R
1
1
C
1
0.1µF
PGOOD
Enable
Mode
C
SS
7
6
5
9
1,2
PVIN
LX
14,15,16
L, 1.0µH
V
OUT
1.5V
C
OUT
47µF
SC185H
4
AVIN
VOUT
PGOOD
EN
MODE
SS
PGND
AGND
11,12,13,T
3
10
June 18, 2010
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SC185
Pin Configuration
LX
PGND
LX
LX
Ordering Information
Device
SC185xULTRT
(2)(3)(4)
SC185xEVB
(5)
12
11
10
Package
3mm x 3mm x 0.6mm MLPQ-UT16
Evaluation Board
16
15
14
13
PVIN
PVIN
AGND
AVIN
1
2
3
4
5
TOP VIEW
PGND
PGND
VOUT
SS
T
9
7
8
6
Notes:
(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) Available in tape and reel only. A reel contains 3,000 devices.
(3) Device is Pb-free, Halogen free, and RoHS/WEEE compliant.
(4) “x” is the code of the output voltage. See Table 1 for the code. For
example, the device number for VOUT= 1.50V is SC185HULTRT.
(5) “x” is the code of the output voltage. See Table 1 for the code. For
example, the EVB with VOUT= 1.50V is SC185HEVB.
3mm x 3mm x 0.6mm MLPQ-UT16
θ
JA
= 40°C/W
(1)
; θ
JC
= 7°C/W
PGOOD
MODE
NC
EN
Marking Information
Table 1: Available Output Voltages
Code
B
VOUT
(6)
1.00
1.20
1.50
1.80
2.50
3.30
185x
E
H
J
L
Q
nnnn
yyww
Notes:
(6) Contact factory for alternative output voltage options.
Marking for 3mm x 3mm MLPQ-UT 16 Lead Package:
x = Code of the output voltage (Example: H for VOUT=1.50V)
yyww = Datecode (Example: 0852)
nnnn = Semtech Lot number (Example: E901)
© 2010 Semtech Corp.
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SC185
Absolute Maximum Ratings
PVIN and AVIN Supply Voltages ………………… -0.3 to 6.0V
LX Voltage
(9)
……………………
-0.3 to PVIN+0.3V, 6V Max
VOUT Voltage …………………………… -0.3 to AVIN+0.3V
CTLx pins Voltages ……………………… -0.3 to AVIN+0.3V
Peak IR Reflow Temperature …………………………. 260°C
ESD Protection Level
(8)
………………………………….
3kV
Recommended Operating Conditions
Supply Voltage PVIN and AVIN …………………… 2.9 to 5.5V
Maximum Output Current
………………………………… 4.0A
Temperature Range …………………………… -40 to +85˚C
Input Capacitor ………………………………………… 22uF
Output Capacitor
Output Inductor
……………………… 47uF (or 2 x 22uF)
……………………………………… 1.0uH
Thermal Information
Thermal Resistance, Junction to Ambient
(7)
………… 40 °C/W
Thermal Resistance, Junction to Case …………… 7 °C/W
Maximum Junction Temperature …………………… +150°C
Storage Temperature Range ………………… -65 to +150 °C
Exceeding the absolute maximum ratings may result in permanent damage to the device and/or device malfunction. Operation outside of the
parameters specified in the Electrical Characteristics section is not recommended.
Notes:
(7) 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.
(8) Tested according to JEDEC standard JESD22-A114-B.
(9) Due to parasitic board inductance, the transient LX pin voltage at the point of measurement may appear larger than that which exists on silicon. The device is
designed to tolerate the short duration transient voltages that will appear on the LX pin due to the deadtime diode conduction, for inductor currents up to the
current limit setting of the device.
Electrical Characteristics
Unless specified: PVIN= AVIN= 5.0V, VOUT= 1.50V, C
IN
= 22µF, C
OUT
= 2 x 22µF; L= 1.0µH; -40°C≤ T
J
≤ +125 °C; Unless otherwise noted typical values are T
A
= +25 °C.
Parameter
Under-Voltage Lockout
Output Voltage Tolerance
(10)
Current Limit
Supply Current
Shutdown Current
High Side Switch Resistance
(11)
Low Side Switch Resistance
(11)
L
X
Leakage Current
(11)
Load Regulation
Oscillator Frequency
Soft-Start Charging Current
(11)
Foldback Holding Current
Symbol
UVLO
Conditions
Rising AVIN, PVIN=AVIN
Hysteresis
Min
2.70
Typ
2.80
300
Max
2.90
Units
V
mV
ΔV
OUT
I
LIMIT
I
Q
I
SHDN
R
DSON_P
R
DSON_N
I
LK(LX)
ΔV
LOAD-REG
f
OSC
I
SS
I
CL_HOLD
PVIN= AVIN= 2.9 – 5.5V; I
OUT
=0A
Peak LX current
No load, MODE= High
No load, MODE= Low
EN= AGND
I
LX
= 100mA, T
J
= 25 °C
I
LX
= -100mA, T
J
= 25 °C
PVIN= AVIN= 5.5V; LX= 0V; EN= AGND
PVIN= AVIN= 5.5V; LX= 5.0V; EN= AGND
PVIN= AVIN= 5.0V, MODE=Hi, I
OUT
=1mA – 4A
-1.25
5.0
6.0
12
100
1
50
35
1
-20
-1
±0.3
1.275
1.5
+5
+1.25
7.0
%
A
mA
µA
10
µA
mΩ
10
µA
%
1.725
MHz
µA
A
Average LX Current
1
© 2010 Semtech Corp.
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SC185
Electrical Characteristics (continued)
Parameter
Impedence of PGOOD Low
PGOOD Threshold
PGOOD Delay
EN Delay
EN Input Current
(11)
EN Input High Threshold
EN Input Low Threshold
MODE Input Current
(11)
MODE Input High Threshold
MODE Input Low Threshold
V
OUT
Over Voltage Protection
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Symbol
R
PGOOD_LO
V
PG_TH
V
PG_DLY
t
EN_DLY
I
EN_
V
EN_HI
V
EN_LO
I
MODE_
V
MODE_HI
V
MODE_LO
V
OVP
T
SD
T
SD_HYS
Conditions
Min
Typ
10
Max
Units
Ω
%
ms
µs
µs
VOUT rising
Asserted
PGOOD= Low
From EN Input High to SS starts rising
EN =AVIN or AGND
-2.0
1.2
90
2
20
50
2.0
µA
V
0.4
MODE= AVIN or AGND
-2.0
1.2
0.4
110
115
160
10
120
2.0
V
µA
V
V
%
°C
°C
Notes:
(10) The “Output Voltage Tolerance” includes output voltage accuracy, voltage drift over temperature and the line regulation.
(11) A negative current means the current flows into the pin and a positive current means the current flows out from the pin.
© 2010 Semtech Corp.
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SC185
Pin Descriptions
Pin #
1,2
3
4
Pin Name
PVIN
AGND
AVIN
Pin Function
Input supply voltage for the converter power stage.
Ground connection for the internal circuitry. AGND needs to be connected to PGND directly.
Power supply for the internal circuitry. AVIN is required to be connected to PVIN through an R-C filter of 1Ω
and 100nF.
MODE select pin. When connected to logic high, the device operates in forced PWM mode. When connected
to logic low, it operates normally with PSAVE mode at light load. The enable pin has a 500kΩ internal pull-
down resistor. This resistor is switched in circuit whenever the MODE pin is “Low” or when the part is in un-
dervoltage lockout.
Enable pin. When connected to logic high or tied to AVIN pin, the SC185 is on. When connected to logic low,
the device enters shutdown and consumes less than 1µA current (typ.). The enable pin has a 500kΩ internal
pulldown resistor. This resistor is switched in circuit whenever the EN is “Low” or when the part is in undervolt-
age lockout.
Power good indicator. When the output voltage reaches the PGOOD threshold, this pin will be open-drain
(After the PGOOD delay), otherwise, it is pulled low internally.
No connection.
Soft Start. Connect a soft-start capacitor to program the soft start time. There is a 5µA charging current flow-
ing out of the pin.
Output voltage sense pin.
Ground connection for converter power stage.
Switching node - connect an inductor between this pin and the output capacitor.
Thermal pad for heatsinking purposes. Recommend to connect it to PGND. It is not connected internally.
5
MODE
6
EN
7
8
9
10
11,12,13
14,15,16
T
PGOOD
NC
SS
VOUT
PGND
LX
Thermal Pad
© 2010 Semtech Corp.
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