600kHz, 3A Step-Down
Switching Regulator
POWER MANAGEMENT
Description
The SC4519H is a current mode switching regulator with
an integrated switch, operating at 600kHz with separate
sync and enable functions. The integrated switch allows
for cost effective low power solutions (peak switch current
3 amps). The sync function allows customers to
synchronize to a faster clock in order to avoid frequency
beating in noise sensitive applications. High frequency
of operation allows for very small passive components.
Current mode operation allows for fast dynamic response
and instantaneous duty cycle adjustment as the input
varies (ideal for CPE applications where the input is a
wall plug power).
The low shutdown current makes it ideal for portable
applications where battery life is important.
The SC4519H is a 600kHz switching regulator
synchronizable to a faster frequency from 750kHz to
1.2MHz.
SC4519H
Features
Integrated 3 Amp switch
600kHz frequency of operation
Current mode controller
Synchronizable to higher frequency up to 1.2MHz
Precision enable threshold
SO-8 EDP package. Lead free product, fully WEEE
and RoHS compliant
Applications
XDSL modems
CPE equipment
DC-DC point of load applications
Portable equipment
Typical Application Circuit
D1
1
VIN
Enable
C3
2
5
8
BST
IN
SW
3
6
7
C1
L1
VOUT
R1
SC4519H
EN
SYNC
GND
4
FB
COMP
D2
R2
C2
C4
R3
Revision: December 12, 2007
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SC4519H
POWER MANAGEMENT
Absolute Maximum Ratings
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.
Parameter
Input Supply Voltage
Boost Pin Above V
SW
Boost Pin Voltage
EN Pin Voltage
FB Pin Voltage
FB Pin Current
SYNC Pin Current
Thermal Impedance Junction to Ambient
Operating Ambient Temperature Range
Maximum Junction Temperature
Storage Temperature Range
Lead Temperature (Soldering) 10 sec
ESD Rating (Human Body Model)
Symbol
V
IN
(V
BST
- V
SW
)
V
BST
V
EN
V
FB
I
FB
I
SYNC
θ
J A
T
A
T
J
T
STG
T
LEAD
ESD
Limits
-0.3 to +28
(1)
16
-0.3 to +32
-0.3 to +24
-0.3 to +6
1
1
36.5
(2)
-40 to +85
+150
-65 to +150
300
2
Units
V
V
V
V
V
mA
mA
°C/W
°C
°C
°C
°C
kV
Notes:
(1) For proper operation of device, V
IN
should be within maximum Operating Input Voltage as defined in Electrical
Characteristics.
(2) ThetaJA is calculated from a package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under exposed
pad per JESD51 standards.
Electrical Characteristics
Unless specified: V
IN
= 12V, V
COMP
= 0.8V, V
BST
= V
IN
+ 5V, EN = tied to V
IN
, SYNC = 0, SW = open.
T
A
= T
J
= -40°C to 125°C.
Parameter
Operating Input Voltage
Maximum Switch Current Limit
Oscillator Frequency
Switch On Voltage Drop
V
IN
Undervoltage Lockout
V
IN
UVLO Hysteresis
V
IN
Supply Current
Standby Current
Symbol
V
IN
I
SW
f
OSC
V
D(SW)
V
UVLO
Conditions
Min
Typ
Max
24
(1)
Units
V
A
kHz
mV
T
A
= 25°C, D = 50%
3.5
500
600
220
3.9
60
5.5
700
I
SW
= 3A
4.4
V
mV
I
Q
I
Q(OFF)
V
FB
= 1V
V
E N
= 0V
3
100
5
150
mA
µA
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SC4519H
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: V
IN
= 12V, V
COMP
= 0.8V, V
BST
= V
IN
+ 5V, EN = tied to V
IN
, SYNC = 0, SW = open.
T
A
= T
J
= -40°C to 125°C.
PARAMETER
FB Input Current
Feedback Voltage
Feedback Voltage Line
Regulation
FB to V
COMP
Voltage Gain
(3)
FB to V
COMP
Transconductance
(3)
V
COMP
Pin Source Current
V
COMP
Pin Sink Current
V
COMP
Pin to Switch Current
Transconductance
V
COMP
Pin Maximum
Switching Threshold
V
COMP
OCP Threshold
V
COMP
Hiccup Retry Threshold
Maximum Switch Duty Cycle
Minimum Boost Voltage
Above Switch
(3)
Boost Current
SYMBOL
I
FB
CONDITIONS
MIN
TYP
-0.25
MAX
-1
0.816
UNITS
µA
V
mV/V
V/V
0.784
4.4V < V
IN
< 24V
(2)
0.9V
≤
V
COMP
≤
2.0V
∆
I
COMP
=
±
10µA
V
FB
= 0.6V
V
FB
= 1.0V
V
COMP
= 1.25V
Duty cycle = 0%
V
COMP
rising
V
COMP
falling
V
COMP
= 1.2V, I
SW
= 400mA
85
150
500
0.8
+3
350
850
70
-70
5
0.6
2
0.25
1300
110
-110
µMho
µA
µA
A/V
V
V
V
%
2.7
I
SW
= 1A
I
SW
= 3A
10
30
15
45
V
mA
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SC4519H
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: V
IN
= 12V, V
COMP
= 0.8V, V
BST
= V
IN
+ 5V, EN = tied to V
IN
, SYNC = 0, SW = open.
T
A
= T
J
= -40°C to 125°C.
PARAMETER
Enable Input Threshold Voltage
Enable Output Bias Current
SYMBOL
V
ETH
I
EOL
I
EOH
CONDITIONS
MIN
1.1
TYP
1.27
8
10
1.5
MAX
1.5
UNITS
V
µA
µA
V
EN = 50mV below threshold
EN = 50mV above threshold
SYNC Threshold Voltage
SYNC Input Frequency
SYNC Pin Resistance
(4)
800
V
SYNC
= 0.5V
20
1200
kHz
kΩ
Notes:
(1) The device may not function properly outside its operating input voltage range.
(2) The required minimum input voltage for a regulated output depends on the output voltage and load condition.
(3) Guaranteed by design.
(4) Please contact factory for SYNC applications.
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SC4519H
POWER MANAGEMENT
Pin Configurations
Ordering Information
Part Number
(1)(2)
SC4519HSETRT
P ackag e
SO-8 EDP
EVALUATION BOARD
TOP VIEW
BST
IN
SW
GND
1
2
3
4
8
7
6
5
SYNC
COMP
FB
EN
SC4519HEVB
(3)
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(2) Lead free product. This product is WEEE and
RoHS compliant.
(3) Consult factory for all other available options.
(SO-8 EDP)
Pin Descriptions
Pin #
1
2
3
4
5
Pin Name Pin Function
BST
IN
SW
GND
EN
This pin provides power to the internal NPN switch. The minimum turn on voltage for this switch
is 2.7V.
Pin IN delivers all power required by control and power circuitry. This pin sees high di/dt during
switching. A decoupling capacitor should be attached to this pin as close as possible.
Pin SW is the emitter of the internal switch. The external freewheeling diode should be connected
as close as possible to this pin.
All voltages are measured with respect to this pin. The decoupling capacitor and the freewheeling
diode should be connected to GND as short as possible.
This is the chip enable input. The regulator is switched on if EN is high, and it is off if EN is low.
The regulator is in standby mode when EN is low, and the input supply current is reduced to a few
microamperes.
Feedback input for adjustable output controllers.
Thi s i s the output of the i nternal error ampli fi er and i nput of the peak current comparator. A
compensation network is connected to this pin to achieve the specified performance.
This is synchronous control pin used to synchronize the internal oscillator to an external pulse
control signal. When not used, it should be connected to GND.
6
7
8
-
FB
COMP
SYNC
THERMAL P ad for heatsi nki ng purposes. C onnect to ground plane usi ng multi ple vi as. Not connected
PAD
internally.
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