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A5970D
Up to 1 A step down switching regulator for automotive applications
Features
Qualified following the AEC-Q100 requirements (temperature grade 3), see PPAP for more details. Up to 1 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 Inhibit for zero current consumption Synchronization Protection against feedback disconnection Thermal shutdown The A5970D is a step down monolithic power switching regulator capable to deliver up to 1 A at output voltages from 1.2 V to 35 V. 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
Dedicated to automotive applications Application schematic
Figure 1.
L1 33uH
VIN=4.4V to 35V
VCC COMP
C4 C1 10uF 35V CERAMIC C3 220pF R3 4k7 22nF
8 4
1 2
OUT SYNCH
Vout=3.3V
A5970D
FB 6 5 7 GND INH 3
D1 STPS340U
R1 5k6 C2 100uF 10V R2 3k3
VREF 3.3V
August 2008
Rev 4
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www.st.com 1
Contents
A5970D
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Packages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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A5970D
1
1.1
Pin settings
Pin connection
Figure 1. Pin connection (top view)
1.2
Pin description
Table 1.
N 1 2 3 4 5 6 7 8
Pin description
Pin OUT SYNCH INH COMP FB VREF GND VCC Regulator output. Master/slave synchronization. A logical signal (active high) disables the device. If INH not used the pin must be grounded. When it is open an internal pull-up disable the device. 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. 3.3 V VREF. No cap is requested for stability. Ground. Unregulated DC input voltage. Description
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Electrical data
A5970D
2
2.1
Electrical data
Maximum ratings
Table 2.
Symbol V8 V1 I1 V4 , V5 V3 V2 PTOT Tj TSTG Input voltage OUT pin DC voltage OUT pin peak voltage at t = 0.1 s Maximum output current Analog pins INH SYNCH 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 -0.3 to VCC -0.3 to 4 0.75 -40 to 150 -55 to 150 V V 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 120 (1) Unit C/W
1. Package mounted on board
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A5970D
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 Test condition V0 = 1.235 V; I0 = 1 A Min 4 0.250 Typ Max 36 0.5 2.25 A 1.5 212 0 1.87 250 2.25 280 100 kHz % Unit V
VCC = 5 V
VCC = 5 V, TJ = 25 C
1.35
1.87
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 Iqst-by Inhibit Device ON INH threshold voltage Device OFF Error amplifier VOH VOL Io source Io sink Ib High level output voltage Low level output voltage Source output current Sink output current Source bias current DC open loop gain RL= 50 VFB = 1 V VFB = 1.5 V
VCOMP = 1.9 V; VFB = 1 V VCOMP = 1.9 V; VFB=1.5 V
Total operating quiescent current Quiescent current Total stand-by quiescent current Duty cycle=0; VFB=1.5 V Vinh > 2.2 V VCC = 36 V; Vinh > 2.2 V
3
5 2.5
mA mA A A
50 80
100 150
0.8 2.2
V V
3.5 0.4 190 1 300 1.5 2.5 65 4
V V A mA A dB
8
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Electrical characteristics Table 4.
Symbol gm
A5970D
Electrical characteristics (continued)
(TJ = -40 to 125 C, VCC =12 V, unless otherwise specified) Parameter Transconductance Test condition ICOMP = -0.1 mA to 0.1 mA; VCOMP = 1.9 V Min Typ 2.3 Max Unit mS
Synch function High input voltage Low input voltage Slave synch current Master output amplitude Output pulse width Reference section Reference voltage Line regulation Load regulation Short circuit current IREF = 0 to 5 mA VCC = 4.4 V to 36 V IREF = 0mA VCC = 4.4 V to 36 V IREF = 0 mA 5 3.2 3.3 5 8 18 3.399 10 15 35 V mV mV mA VCC= 4.4 to 36 V; VCC= 4.4 to 36 V; Vsynch= 0.74 V Vsynch= 2.33 V Isource= 3 mA no load, Vsynch= 1.65 V
(2)
2.5
VREF 0.74
V V mA V s
0.11 0.21 2.75 0.20 3 0.35
0.25 0.45
1. With TJ = 85 C, Ilim_min = 1.5 A, assured by design, characterization and statistical correlation. 2. Guaranteed by design
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A5970D
4
Figure 2.
Typical characteristics
Junction temperature vs output current Figure 3. Load regulation
Figure 4.
Junction temperature vs output voltage
Figure 5.
Line regulation
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Typical characteristics Figure 6. Junction temperature vs output current Figure 7. Output voltage vs junction temperature
A5970D
Figure 8.
Quiescient current vs junction temperature
Figure 9.
Switching frequency vs junction temperature
8/11
A5970D Figure 10. Shutdown current vs junction temperature Figure 11. Efficiency vs output current
Figure 12. Efficiency vs output current
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Package mechanical data
A5970D
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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A5970D
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 0.1890 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 ccc
1.35 0.10 1.10 0.33 0.19 4.80 3.80
0 (min), 8 (max) 0.10 0.0039
Figure 13. Package dimensions
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Revision history
A5970D
6
Revision history
Table 6.
Date 06-Aug-2007 24-Oct-2007 2-May-2008 27-Aug-2008
7
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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A5970D
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