STMICROELECTRONICS L5988

L5988
4A step-down switching regulator
with synchronous rectification
Preliminary Data
Features
■
4A DC output current
■
2.9V to 18V input voltage
■
Output voltage adjustable from 0.6V
■
400KHz switching frequency, programmable
up to 1MHz
■
Soft-start and inhibit
■
1.8V ± 2% reference voltage
■
Low dropout operation: 100% duty cycle
■
Voltage feed-forward
■
Zero load current operation
■
Sink current capability
■
Over current, over voltage and thermal
protection
■
HTSSOP16 package
HTSSOP16
Applications
■
Consumer:
– STB, DVD, DVD recorder, TV, VCR, Car
audio, LCD monitors
■
Networking:
– XDSL, Modems, DC-DC modules
■
Computer:
– Optical storage, Hard disk drive, Printers,
Audio/Graphic cards
■
Industrial:
– Chargers, car battery, DC-DC converters
Application circuit
Order codes
Part Number
Package
Packaging
L5988D
HTSSOP16
Tube
L5988DTR
HTSSOP16
Tape and reel
August 2006
Rev 3
1/10
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
www.st.com
10
L5988
Contents
Contents
1
Technical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Pin connections and functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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L5988
1
Technical characteristics
Technical characteristics
The L5988D is a synchronous step down monolithic power switching regulator capable of
delivering up to 4A. The input voltage can range from 2.9V to 18V.
Thanks to the very short minimum ON time, the device is able to manage extremely low duty
cycles, allowing very low output voltages. Requiring a minimum set of external components, the
device includes an internal 400 KHz switching frequency oscillator that can be externally
adjusted up to 1MHz. The regulator can provide 100% duty-cycle. A multifunction pin allows to
enable-disable the sink mode current capability after soft-start, to enable-disable the latch
mode for the OVP and to set the UVLO threshold for the 3.3V BUS and 12V BUS. The current
limit can be externally adjusted to fit the application requirements. The current is sensed during
both the on-time and the off-time and so the protection is effective with both very low or very
high duty-cycle and/or with high switching frequency. The HTSSOP16 package with exposed
pad allows reducing the RthJA to 40°C/W
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L5988
Pin connections and functions
2
Pin connections and functions
Figure 1.
Table 1.
Pin connection ( Top view)
VOUT
1
16
VOUT
VCC
2
15
GND
VCC
3
14
GND
VCC
4
13
GND
SS/INH
5
12
VREF
COMP
6
11
OUS
ILIM-ADJ
7
10
FSW
FB
8
9
SYNCH
Pin functions
No Pin
Name
2,3,4
VCC
Unregulated DC input voltage.
1,16
VOUT
Regulator output.
13,14,15
GND
Ground.
9
SYNCH
It is a Master-Slave pin. Two or more devices can be synchronized by simply connecting the
SYNCH pins together. The device operating with the highest FSW will be the Master. The
Slave devices will operate with 180° phase shift from the Master.
10
FSW
Connecting an external resistor from this pin to GND, the external frequency can be increased
up to 1 MHz. Connecting an external resistor from this pin to VREF (1.8V), the switching
frequency can be decreased down to 200 KHz. If the pin is left open, the default switching
frequency is 400 KHz. The pin voltage is 1.2V. In OVP the pin is pulled up to 3.3V (only in
latched mode).
8
FB
This pin is connected to the error amplifier inverting input. Connect it to the output resistor
divider (if used) or directly to Vout. This pin is also used to sense the output voltage in order to
manage the over voltage condition.
6
COMP
This pin is connected to the error amplifier output and is used to compensate the voltage
control feedback loop.
5
SS/INH
The soft-start time is programmed connecting an external capacitor from this pin and GND.
The internal current generator forces a current of 22 µA through the capacitor. When the
voltage at this pin is lower than 0.65V the device is disabled.
12
VREF
7
11
Description
Internally regulated voltage of 1.8V. It is used to provide a voltage reference for the
multifunction pin. Filter this pin to ground with at least 1µF ceramic cap.
Connecting a resistor between this pin and GND it is possible to increase the over current
ILIM-ADJ protection threshold. Connecting a resistor between this pin and VREF it is possible to
decrease the over current protection threshold.
S/O/U
Multifunction pin. Depending on the voltage level at the input, with this pin it is possible:
– to enable-disable the sink mode current capability after soft-start;
– to enable-disable the latch mode for the OVP;
– to set the UVLO threshold for the 3.3V BUS and 12V BUS. (2.4V and 8V respectively);
The device continuously checks the analog value present at this pin and sets the
function according with the measured voltage.
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L5988
3
Maximum ratings
Maximum ratings
Table 2.
Absolute maximum ratings
Symbol
Parameter
VCC
Input voltage
VOUT
Output DC voltage
S/O/U, SS/INH, FB, COMP,
Analog pins
SYNCH, Fsw, ILIM-ADJ
Unit
20
V
-0.3 to 20
V
-0.3 to 4
V
Power dissipation at TA = 60°C
PTOT
4
Value
W
TJ
Junction temperature range
-40 to 150
°C
Tstorage
Storage temperature range
-55 to 150
°C
Electrical characteristics
VCC = 12V, TJ = 25° C, unless otherwise specified
Table 3.
Symbol
VCC
Electrical characteristics
Parameter
Operating input voltage range
Test condition
VO = 0.6V
Min
Typ
2.9
Max
Unit
18
V
Rdson_hs
On resistance high-side MOSFET
75
mΩ
Rdson_ls
On resistance low-side MOSFET
60
mΩ
ILIM-ADJ = float
4
A
R = 270KΩ to GND
5
A
R = 47KΩ to VREF
1.3
A
ILIM-ADJ = float
4.6
A
R = 270KΩ to GND
5.6
A
R = 47KΩ to VREF
1.8
A
SS to GND
35
µA
Turn-On VCC threshold
2.8
V
Turn-Off VCC threshold
2.6
V
Turn-On VCC threshold
8
V
Turn-Off VCC threshold
7
V
II peak
II valley
Iqst-by
Current limit
Current limit
Total shutdown quiescent current
Power-ON
3.3V BUS
12V BUS
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L5988
Electrical characteristics
Table 3.
Electrical characteristics
Symbol
Parameter
Test condition
Min
Typ
Max
Unit
Soft start and inhibit
Iss
Soft start current
SS = 2V
18
µA
Inhibit current
SS = 0V
5
µA
Device ON level
0.8
V
Device OFF level
0.3
V
Oscillator
fS
Switching frequency
FSW = open
Duty cycle (1)
400
0
KHz
100
%
Voltage feedback
VFB
Output voltage
2.9V < VCC < 18V
Output voltage
VSS = 3V
Bias current
VFB = 0V to 2.5V
0.6
V
Error amplifier
VCOMP
IFB
Io source
Io sink
VCM
VOFFSET
GV
0
3
V
0.290
µA
Source output pin
25
mA
Sink output pin
40
mA
Common mode voltage
Error amplifier offset
Vref = 0.6V
Open loop voltage gain
0
2.3
V
-5
+5
mV
100
dB
Reference section
VREF
Reference voltage
Iref = 0 to 5mA
VCC = 2.9 to 18V
1.8
V
Line regulation
Iref = 0 mA
VCC = 2.9 to 18V
6
mV
Load regulation
Iref = 0 to 5mA
7.5
mV
12
mA
20
%
Short circuit current
Protections
Over voltage trip
(VFB / 0.6V int. ref.)
1. Guaranteed by design
6/10
VFB Rising
L5988
5
Package mechanical data
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK® packages.
These packages have a Lead-free second level interconnect . The category of second Level
Interconnect is marked on the package and on the inner box label, in compliance with JEDEC
Standard JESD97. The maximum ratings related to soldering conditions are also marked on
the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at:
www.st.com.
7/10
L5988
Table 4.
Package mechanical data
TSSOP16 exposed pad mechanical data
Dim.
mm.
Min
Typ
Inch
Max
A
1.2
A1
0.15
A2
0.8
b
Typ
Max
0.047
0.004
0.006
0.039
0.041
1.05
0.031
0.19
0.30
0.007
0.012
c
0.09
0.20
0.004
0.0089
D
4.9
5.1
0.193
D1
1.7
E
6.2
6.4
6.6
E1
4.3
4.4
4.5
E2
1.5
e
5
0.197
0.201
0.244
0.252
0.260
0.169
0.173
0.177
0.067
0.059
0.65
K
0°
L
0.45
Figure 2.
1
Min
0.60
0.0256
8°
0°
0.75
0.018
8°
0.024
0.030
Package dimensions
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L5988
6
Revision history
Revision history
Table 5.
Revision history
Date
Revision
Changes
25-Nov-2005
1
Initial release
10-Jan-2006
2
Various updates on Table 1
08-Aug-2006
3
Added Electrical data Table 3.
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L5988
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