ST750A
Adjustable step-down, current-mode PWM DC-DC converters
Features
Up to 450mA load currents 200kHz high-frequency current-mode PWM 85% to 96% efficiencies 33mH or 100mH pre-selected inductor value, no component design required 0.8mA quiescent current 0.3A shutdown supply current Adjustable output voltage Overcurrent, soft-start and undervoltage lockout protection Cycle-by-cycle current limiting Package available: SO-8 provides precise output regulation and excellent transient responses. Output voltage accuracy is guaranteed to be 4.5% plus feedback resistor tolerance over line, load, and temperature variations. Fixed-frequency switching and absence of subharmonic ripple allows easy filtering of output ripple and noise, as well as the use of small external components. This regulators require only a single inductor value to work in most applications, so no inductor design is necessary. Typical applications are: Cellular phones & radios, portable Instruments, Portable Communications Equipment and Computer Peripherals.
SO-8
Description
The ST750A is an adjustable output CMOS, stepdown switching regulator. The ST750A accepts inputs between 4V and 11V and delivers 450mA. Typical efficiencies are 85% to 96%. Quiescent supply current is 0.8mA and only 0.3mA in shutdown mode. The output does not exhibit frequency over this specified range. Pulsewidth modulation (PWM) current-mode control
Order code
Part number ST750AC May 2007 Rev. 3 Packaging ST750ACDTR 1/14
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ST750A
Contents
1 2 3 4 5 6 7 8 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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ST750A
Diagram
1
Figure 1.
Diagram
Schematic diagram
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Pin configuration
ST750A
2
Figure 2.
Pin configuration
Pin connections (top view)
Table 1.
Pin N 1 2 3 4 5 6 7 8
Pin description
Symbol SHDN REF SS CC IC GND LX VCC Name and function Shutdown control (active low): If connected to GND the IC is in shutdown. Connect to VCC for normal operation (ON MODE) Reference output voltage: (1.25V): Bypass to GND with a capacitor that does not exceed 47nF Soft start: a capacitor between SS and GND provides soft-start and short-circuit protections. Compensation capacitor input: externally compensates the outer (voltage) feedback loop. Connect to OUT with 330pF capacitor Internal connection: make no external connection to this pin Ground Switch output. Drain of internal P-channel power MOSFET Supply voltage input. Bypass to GND with 1F ceramic capacitance and large value electrolytic capacitor in parallel. The 1F capacitor must be as close as possible to the GND and VCC pins
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ST750A
Maximum ratings
3
Table 2.
Symbol VCC VLX VSHDN VS,VC ILX IREF PTOT Tstg Top
Maximum ratings
Absolute maximum ratings
Parameter DC Input voltage Switch pin voltage Shutdown voltage (SHDN) Soft start (SS) and compensation capacitor (CC) pins voltage Switching peak current Reference current Continuous power dissipation at TA=70C Storage temperature range Operating junction temperature range C series SO-8 Value -0.3 to 12 -0.3 to (VCC + 0.3) -0.3 to (VCC + 0.3) -0.3 to (VCC + 0.3) 2 2.5 344 -40 to +150 0 to +70 Unit V V V V A mA mW C C
Note:
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is not implied Thermal data
Parameter Thermal resistance junction-ambient (1) SO-8 160 Unit C/W
Table 3.
Symbol RthJA
1. This value depends from thermal design of PCB on which the device is mounted.
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Typical application
ST750A
4
Figure 3.
Typical application
Application circuit
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ST750A
Electrical characteristics
5
Table 4.
Symbol VCC VO VO VO
Electrical characteristics
Electrical characteristics (VCC=5V, IO = 0mA, TA = TMIN to TMAX, unless otherwise specified).
Parameter Input voltage Output voltage Line regulation Load regulation Power efficiency VCC = 6 to 11V, IO = 0 to 450mA VCC = 4 to 11V IO = 0 to 450mA IO = 300mA ON Mode Test conditions Min. 4 4.75 5 0.15 0.005 92 0.8 0.3 2 VCC Falling 0.25 1 2.7 0.5 1 1.17 1.24 50 C series 160 200 7500 280 1.31 3 2.5 100 Typ. Max. 11 5.25 Unit V V %/V %/mA % mA A V V A V A V ppm/C KHz
ISUPPLY Supply current VIH VIL ISHDN VLOCK SHDN Input high threshold SHDN Input low threshold
OFF Mode, SHDN = 0
Shutdown input leakage current ILX = 500mA Under voltage lockout VCC = 12V, VLX = 0V TA = 25C
RDS(on) LX On resistance ILX VREF VREF fOSC RC LX Leakage current Reference voltage Temperature reference drift Switching frequency Compensation pin impedance
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Typical performance characteristics
ST750A
6
Figure 4.
Typical performance characteristics
(Unless otherwise specified TJ = 25C) Efficiency vs output current Figure 5. Supply current vs temperature
Figure 6.
Oscillator frequency vs temp.
Figure 7.
Oscillator frequency vs input volt.
Figure 8.
Peak inductor current vs out. curr.
Figure 9.
Output voltage vs output current
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ST750A
Typical performance characteristics
Figure 10. Switching waveforms, continuous conduction
Figure 11. Switching waveforms, discontinuous conduction
VI = 6V to 11V, IO = 300mA
VI = 6V to 11V, IO = 300mA
Figure 12. Line transient
Figure 13. Load transient
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Package mechanical data
ST750A
7
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.
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ST750A
Package mechanical data
SO-8 MECHANICAL DATA
DIM. A A1 A2 B C D E e H h L k ddd 0.1 5.80 0.25 0.40 mm. MIN. 1.35 0.10 1.10 0.33 0.19 4.80 3.80 1.27 6.20 0.50 1.27 0.228 0.010 0.016 TYP MAX. 1.75 0.25 1.65 0.51 0.25 5.00 4.00 MIN. 0.053 0.04 0.043 0.013 0.007 0.189 0.150 0.050 0.244 0.020 0.050 inch TYP. MAX. 0.069 0.010 0.065 0.020 0.010 0.197 0.157
8 (max.)
0.04
00160 23/C
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Package mechanical data
ST750A
Tape & Reel SO-8 MECHANICAL DATA
mm. DIM. MIN. A C D N T Ao Bo Ko Po P 8.1 5.5 2.1 3.9 7.9 12.8 20.2 60 22.4 8.5 5.9 2.3 4.1 8.1 0.319 0.216 0.082 0.153 0.311 TYP MAX. 330 13.2 0.504 0.795 2.362 0.882 0.335 0.232 0.090 0.161 0.319 MIN. TYP. MAX. 12.99 2 0.519 inch
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ST750A
Revision history
8
Table 5.
Date
Revision history
Revision history
Revision 3 Changes Order code has been updated and the document has been reformatted.
29-May-2007
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ST750A
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