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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 L5988D L5988DTR August 2006 Package HTSSOP16 HTSSOP16 Rev 3 Packaging Tube Tape and reel 1/10
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This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. www.st.com
Contents
L5988
Contents
1 2 3 4 5 6 Technical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin connections and functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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L5988
Technical characteristics
1
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 40C/W
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Pin connections and functions
L5988
2
Figure 1.
Pin connections and functions
Pin connection ( Top view)
VOUT VCC VCC VCC SS/INH COMP ILIM-ADJ FB
Table 1.
No Pin 2,3,4 1,16 13,14,15 9
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9
VOUT GND GND GND VREF OUS FSW SYNCH
Pin functions
Name VCC VOUT GND SYNCH Unregulated DC input voltage. Regulator output. Ground. 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. 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). 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. This pin is connected to the error amplifier output and is used to compensate the voltage control feedback loop. The soft-start time is programmed connecting an external capacitor from this pin and GND. The internal current generator forces a current of 22 A through the capacitor. When the voltage at this pin is lower than 0.65V the device is disabled. 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 1F ceramic cap. Description
10
FSW
8
FB
6
COMP
5
SS/INH VREF
12
7
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. 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);
11
S/O/U
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
Maximum ratings
3
Table 2.
Maximum ratings
Absolute maximum ratings
Symbol VCC VOUT Input voltage Output DC voltage Parameter Value 20 -0.3 to 20 -0.3 to 4 Unit V V V W -40 to 150 -55 to 150 C C
S/O/U, SS/INH, FB, COMP, Analog pins SYNCH, Fsw, ILIM-ADJ PTOT TJ Tstorage Power dissipation at TA = 60C Junction temperature range Storage temperature range
4
Electrical characteristics
VCC = 12V, TJ = 25 C, unless otherwise specified
Table 3.
Symbol VCC Rdson_hs Rdson_ls
Electrical characteristics
Parameter Operating input voltage range On resistance high-side MOSFET On resistance low-side MOSFET ILIM-ADJ = float Test condition VO = 0.6V Min 2.9 75 60 4 5 1.3 4.6 5.6 1.8 35 Typ Max 18 Unit V m m A A A A A A A
II peak
Current limit
R = 270K to GND R = 47K to VREF ILIM-ADJ = float
II valley
Current limit
R = 270K to GND R = 47K to VREF
Iqst-by Power-ON 3.3V BUS
Total shutdown quiescent current
SS to GND
Turn-On VCC threshold Turn-Off VCC threshold
2.8 2.6 8 7
V V V V 5/10
12V BUS
Turn-On VCC threshold Turn-Off VCC threshold
Electrical characteristics
L5988
Table 3.
Symbol
Electrical characteristics
Parameter Test condition Min Typ Max Unit
Soft start and inhibit Iss Soft start current Inhibit current Device ON level Device OFF level Oscillator fS Switching frequency Duty cycle (1) Voltage feedback VFB Error amplifier VCOMP IFB Io source Io sink VCM VOFFSET GV Output voltage Bias current Source output pin Sink output pin Common mode voltage Error amplifier offset Open loop voltage gain Vref = 0.6V 0 -5 100 VSS = 3V VFB = 0V to 2.5V 0 0.290 25 40 2.3 +5 3 V A mA mA V mV dB Output voltage 2.9V < VCC < 18V 0.6 V FSW = open 0 400 100 KHz % SS = 2V SS = 0V 0.8 0.3 18 5 A A V V
Reference section VREF Reference voltage Iref = 0 to 5mA VCC = 2.9 to 18V Iref = 0 mA VCC = 2.9 to 18V Iref = 0 to 5mA 1.8 V
Line regulation Load regulation Short circuit current Protections Over voltage trip (VFB / 0.6V int. ref.)
1. Guaranteed by design
6 7.5 12
mV mV mA
VFB Rising
20
%
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L5988
Package mechanical data
5
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) 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.
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L5988
Package mechanical data
Table 4.
Dim.
TSSOP16 exposed pad mechanical data
mm. Min Typ Max 1.2 0.15 0.8 0.19 0.09 4.9 1.7 6.2 4.3 1.5 0.65 0 0.45 0.60 8 0.75 0 0.018 0.024 6.4 4.4 6.6 4.5 5 1 1.05 0.30 0.20 5.1 0.031 0.007 0.004 0.193 0.067 0.244 0.169 0.059 0.0256 8 0.030 0.252 0.173 0.260 0.177 0.197 0.004 0.039 Min Inch Typ Max 0.047 0.006 0.041 0.012 0.0089 0.201
A A1 A2 b c D D1 E E1 E2 e K L
Figure 2.
Package dimensions
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L5988
Revision history
6
Revision history
Table 5.
Date 25-Nov-2005 10-Jan-2006 08-Aug-2006
Revision history
Revision 1 2 3 Initial release Various updates on Table 1 Added Electrical data Table 3. Changes
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L5988
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