SC172
POWER MANAGEMENT
Features
2A EcoSpeed
TM
Synchronous Step-Down
Regulator with Optional Ultrasonic Power Save
Description
The SC172 is an integrated, synchronous 2A EcoSpeed
TM
step-down regulator, which incorporates Semtech’s
advanced, patented adaptive on-time architecture to
achieve best-in-class performance in dynamic point-of-
load applications. The input voltage range is 3V to 5.5V
with a programmable output voltage from 0.75V up to
95% x V
IN
. The device features low-R
DS(ON)
internal switch-
es and optional PSAVE mode for high efficiency across
the output load range.
Adaptive on-time control provides programmable pseu-
do-fixed frequency operation and excellent transient
performance. The switching frequency can be set from
200kHz to 1MHz - allowing the designer to reduce exter-
nal LC filtering and minimize light load (standby) losses.
Disabling PSAVE operation reduces output voltage ripple
at light load for ceramic output capacitors.
Additional features include cycle-by-cycle current limit,
soft start, input UVLO and output OV protection, and
over temperature protection. The open-drain PGOOD
pin provides output status. Standby current is less than
10μA when disabled.
The device is available in a low profile, thermally en-
hanced MLPD-3x3mm 10-pin package.
V
IN
: 3V to 5.5V
V
OUT
: 0.75V to 95% x V
IN
I
OUT
: Up to 2A
Low R
DS(ON)
Switches
Up to 95% Peak Efficiency
High Output Accuracy
Small Ceramic Capacitors
Power Good Pin (Open-Drain)
Patented Adaptive On-Time Control:
Excellent Transient Response
Programmable Pseudo-fixed Frequency
Fault Protection Features:
Cycle-by-Cycle Current Limit
Short Circuit Protection
Over and Under Output Voltage Protection
Over-Temperature
Internal Soft start
Ultrasonic Power Save
Smart Power Save
Ultra-Small Lead-Free 3x3mm, 10-Pin MLPD Package
Fully WEEE and RoHS Compliant
Applications
Networking Equipment, Embedded Systems
Medical Equipment, Office Automation
Instrumentation, Portable Systems
Consumer Devices (DTV, Set-top Box, ... )
5V POL Converters
Typical Application Circuit
3 to 5.5V
VIN
BST
LX
VOUT = 0.75V to 95% VIN
SC172
VDD
FB
PGOOD
Power Good
Enable /
Power Save
EN/PSV
PGND
TON
AGND
October 11 , 2010
© 2010 Semtech Corporation
1
SC172
Pin Configuration
Ordering Information
Device
SC172MLTRT
(1)
Top Mark
172
Package
(2)
MLPD-10 3x3
Evaluation Board
BST
VIN
LX
PGND
PGOOD
VDD
AGND
TON
EN/PSV
FB
SC172EVB
Notes:
1) Available in tape and reel packaging only. A reel contains 3000
devices.
2) Available in lead-free packaging only. WEEE compliant and Halogen
free. This component and all homogenous sub-components are RoHS
compliant.
10 Pin MLPD
θ
JA
= 40°C/W.
Marking Information
TOP MARKING
172
yyww
xxxx
yyww = Date Code(Example: 0952)
xxxx = Semtech Lot Number(Example: 3901)
© 2010 Semtech Corporation
2
SC172
Absolute Maximum Ratings
LX to GND
(3)
……………………… - 0.3(DC) to +6.0V(DC) Max
VIN to PGND, EN/PSV to AGND ………………… -0.3 to +6.0V
VIN to VDD…………………………………………………+0.3V
BST to LX ………………………………………… -0.3 to +6.0V
BST to PGND……………………………………
-0.3 to +12V
VDD to AGND, VOUT to AGND………………… -0.3V to +6.0V
FB, PGOOD, TON …………………………… -0.3 to VDD + 0.3V
AGND to PGND………………………………… -0.3 to +0.3V
Peak IR Reflow Temperature ……………….…………… 260°C
ESD Protection Level
(2)
………………………………………2kV
Recommended Operating Conditions
Supply Input Voltage……………………………… 3V to 5.5V
Maximum Continuous Output Current …………………… 2A
Thermal Information
Storage Temperature …………………………… -60 to +150°C
Maximum Junction Temperature ……………………… 150°C
Operating Junction Temperature ……………… -40 to +125°C
Thermal Resistance, Junction to Ambient
(1)
………… 40°C/W
Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not recommended.
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) Tested according to JEDEC standard JESD22-A114-B
(3) 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. See application section for details.
Electrical Characteristics
Parameter
Input Supplies
VIN, VDD Input Voltage
VDD UVLO Threshold
VDD UVLO Hysteresis
Unless specified: V
IN
=5V, T
A
=+25°C for Typ, -40°C to +85°C for Min and Max, T
J
< 125°C
Symbol
Conditions
Min
Typ
Max
Units
3
Rising UVLO V
TH
2.75
100
EN/PSV= 0V
2.85
200
5
744
1000
5.5
2.98
V
V
mV
15
μA
VIN, VDD Supply Current
I
OUT
=0A, PSAVE, f
SW
=25kHz
(1)
Forced Continuous Conduction Mode
EN floating, I
OUT
=0A , Not Switching
Controller
FB On-Time Threshold
Frequency Programming Range
FB Input Bias Current
© 2010 Semtech Corporation
See R
TON
Calculation
FB=VDD or 0V
0.7425
200
-1
0.75
0.7575
1000
+1
V
kHz
μA
3
SC172
Electrical Characteristics (continued)
Unless specified: V
IN
=5V, T
A
=+25°C for Typ, -40°C to +85°C for Min and Max, T
J
< 125°C
Parameter
Timing
On-Time
Minimum On-Time
(1)
Minimum Off-Time
(1)
Symbol
Conditions
Min
Typ
Max
Units
Continuous Mode
V
IN
=5V, V
OUT
=3V, R
TON
=66.7kΩ
0.9
1
80
250
1.1
μ
s
ns
ns
Soft start
Soft start Time
(1)
Delay from PWM Switching to Output
Regulation
850
μs
Ultrasonic Power Save
Zero-Crossing Detector Threshold
Ultrasonic Power Save Frequency
LX - PGND
0
25
mV
kHz
Power Good
Power Good Signal Threshold High
Power Good Threshold
Power Good Signal Threshold Low
VDD=3V
PGOOD Delay Time
(1)
116
86
120
90
1
124
%V
OUT
93
ms
VDD=5V
2
5
1
10
20
µs
µA
Ω
Noise Immunity Delay Time
Leakage
Power Good On-Resistance
Fault Protection
Output Under-Voltage Fault
Output Over-Voltage Fault
Smart PowerSave
Protection Threshold
OV, UV Fault Noise Immunity Delay
Over-Temperature Shutdown
OT Latched
FB with Respect to REF,
8 Consecutive Clocks
FB with Respect to REF
FB with Respect to REF
-30
+16
+7
-25
+20
+10
5
150
-20
+24
+13
%
%
%
μs
°C
© 2010 Semtech Corporation
4
SC172
Electrical Characteristics (continued)
Unless specified: V
IN
=5V, T
A
=+25°C for Typ, -40°C to +85°C for Min and Max, T
J
< 125°C
Parameter
Enable/Power Save
Output Enabled
Output Disabled
EN/PSV Input Bias Current
Power Save Enabled
Forced Continuous Conduction Mode
Symbol
Conditions
Min
Typ
Max
Units
1
0.4
EN/PSV = VDD or 0V
60
EN/PSV floating
39
41
44
0.5
8.0
V
V
μA
%V
DD
%V
DD
Gate Drivers
BST Switch On resistance
40
75
Ω
Internal Power MOSFETs
Valley Current Limit, VDD=5V
Current Limit
Valley Current Limit, VDD=3V
LX Leakage Current
Switch Resistance
Low Side
Non-overlap time
(1)
75
30
120
ns
VIN=5.5V, LX=0V, High Side
High Side
2
2.4
1
95
10
150
mΩ
µA
2.5
3.2
A
Note:
(1) Typical value from EVB, not ATE tested.
© 2010 Semtech Corporation
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