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A5972D
Up to 1.5 A step down switching regulator for automotive applications
Features
Qualified following the AEC-Q100 requirements (temperature grade 3), see PPAP for more details. 1.5 A DC output current Operating input voltage from 4 V to 36 V Output voltage adjustable from 1.235 V to 35 V Low dropout operation: 100 % duty cycle 250 kHz Internally fixed frequency Voltage feedforward Zero load current operation Internal current limiting Protection against feedback disconnection Thermal shutdown The A5972D is a step down monolithic power switching regulator with a minimum switch current limit of 1.8 A so it is able to deliver more than 1.5 A DC current to the load depending on the application conditions. The output voltage can be set from 1.235V to 35V. The device uses an internal P-channel D-MOS transistor (with a typical RDS(on) of 250 m) as switching element to minimize the size of the external components. An internal oscillator fixes the switching frequency at 250 kHz. Having a minimum input voltage of 4 V only, it is particularly suitable for 5 V bus. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection. SO-8

Description
Applications
Automotive applications
Figure 1.
Application schematic
33uH
VIN=4.4V to 35V
VCC COM P OUT
VO UT=3.3V
C4 C1 10uF C3 220pF 4.7K R3 22nF
A5972D
GND FB
D1 STPS2L40U
R1 5.6K
C2 100uF
R2 3.3K
August 2008
Rev 4
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www.st.com 1
A5972D
Contents
Contents
1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 1.2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 2.2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 4 5 6
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
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A5972D
1
1.1
Pin settings
Pin connection
Figure 1. Pin connection (top view)
1.2
Pin description
Table 1.
N 1 2,3,6,7 4 5 8
Pin description
Pin OUT GND COMP FB VCC Regulator output. Ground. E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1.23 V. An extenal resistive divider is required for higher output voltages. Unregulated DC input voltage. Description
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Electrical data
A5972D
2
2.1
Electrical data
Maximum ratings
Table 2.
Symbol V8 V1 I1 V4 , V5 PTOT TJ TSTG Input voltage OUT pin DC voltage OUT pin peak voltage at t = 0.1 s Maximum output current Analog pins Power dissipation at TA 70 C Operating junction temperature range Storage temperature range
Absolute maximum ratings
Parameter Value 40 -1 to 40 -5 to 40 int. limit. 4 1.2 -40 to 150 -55 to 150 V W C C Unit V V V
2.2
Thermal data
Table 3.
Symbol RthJA
Thermal data
Parameter Maximum thermal resistance junction-ambient SO8 65
(1)
Unit C/W
1. Package mounted on board
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A5972D
3
Electrical characteristics
Table 4.
Symbol VCC RDS(on) IL fSW
Electrical characteristics (TJ = -40 to 125 C, VCC = 12 V, unless otherwise specified)
Parameter Operating input voltage range Mosfet on resistance Maximum limiting current (1) Switching frequency Duty cycle VCC = 5 V VCC = 5 V, TJ = 25 C 1.8 2 212 0 Test condition V0 = 1.235 V; I0 = 2 A Min 4 0.250 2.5 2.5 250 Typ Max 36 0.5 3 A 3 280 100 kHz % Unit V
Dynamic characteristics (see test circuit) V5 Voltage feedback Efficiency 4.4 V < VCC < 36 V, 20 mA < I0 < 2 A V0 = 5 V, VCC = 12 V 1.198 1.235 90 1.272 V %
DC characteristics Iqop Iq Total operating quiescent current Quiescent current Duty cycle = 0; VFB= 1.5 V 3 5 2.5 mA mA
Error amplifier VOH VOL Io source High level output voltage Low level output voltage Source output current VFB = 1 V VFB = 1.5 V VCOMP = 1.9 V; VFB = 1 V VCOMP = 1.9 V; VFB = 1.5 V Source bias current DC open loop gain gm Transconductance RL= 50 2.5 65 2.3 4 A dB mS 1 1.5 190 300 3.5 0.4 V V A
Io sink Ib
Sink output current
mA
ICOMP = -0.1 mA to 0.1 mA; VCOMP = 1.9 V
1. With TJ = 85 C, Ilim_min = 2 A, assured by design, characterization and statistical correlation.
8
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Typical characteristics
A5972D
4
Typical characteristics
Figure 2. Output voltage vs junction temperature Figure 3. Quiescent current vs junction temperature
Figure 4.
Line regulatior
Figure 5.
Shutdown current vs junction temperature
Figure 6.
Output voltage vs junction temperature
Figure 7.
Junction temperature vs output current
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A5972D Figure 8. Junction temperature vs output current Figure 9. Efficiency vs output current
Figure 10. Efficiency vs output current
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Package mechanical data
A5972D
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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A5972D
Table 5.
Dim
SO-8 mechanical data
mm Min Typ Max 1.75 0.25 1.65 0.51 0.25 5.00 4.00 1.27 5.80 0.25 0.40 6.20 0.50 1.27 0.228 0.010 0.016 Min 0.053 0.004 0.043 0.013 0.007 0.189 0.15 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
A A1 A2 B C D (1) E e H h L k ddd
1.35 0.10 1.10 0.33 0.19 4.80 3.80
0 (min), 8 (max) 0.10 0.004
1. Dimension D does not include mold flash, protrusions or gate burrs. Mold flash, protrusions or gate burrs shall not exceed 0.15mm (0.006 inch) in total (both side).
Figure 11. SO-8 mechanical data
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Revision history
A5972D
6
Revision history
Table 6.
Date 06-Aug-2007 5-Nov-2007 2-May-2008 27-Aug-2008
Document revision history
Revision 1 2 3 4 Initial release Updated: Table 4 on page 5 Updated: Cover page, Table 4 on page 5 Updated: Coverpage and Table 4 on page 5 Changes
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A5972D
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