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PDF A6985F Data sheet ( Hoja de datos )
| Número de pieza | A6985F | |
| Descripción | synchronous step-down switching regulator | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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A6985F
38 V 500 mA synchronous step-down switching regulator
with 30 µA quiescent current
Datasheet - production data
HTSSOP16 (RTH = 40 °C/W)
Features
AECQ100 qualification
0.5 A DC output current
4 V to 38 V operating input voltage
Low consumption mode or low noise mode
30 µA IQ at light-load (LCM VOUT = 3.3 V)
8 µA IQ-SHTDWN
Fixed output voltage (3.3 V and 5 V) or
adjustable from 0.85 V to VIN
Adjustable fSW (250 kHz - 2 MHz)
Embedded output voltage supervisor
Synchronization
Adjustable soft-start time
Internal current limiting
Overvoltage protection
Output voltage sequencing
Peak current mode architecture
RDSON HS = 360 m, RDSON LS = 150 m
Thermal shutdown
Description
The A6985F automotive grade device is a step-
down monolithic switching regulator able to
deliver up to 0.5 A DC. The output voltage
adjustability ranges from 0.85V to VIN. The 100%
duty cycle capability and the wide input voltage
range meet the cold crank and load dump
specifications for automotive systems. The “Low
Consumption Mode” (LCM) is designed for
applications active during car parking, so it
maximizes the efficiency at light-load with
controlled output voltage ripple. The “Low Noise
Mode” (LNM) makes the switching frequency
constant and minimizes the output voltage ripple
overload current range, meeting the low noise
application specification like car audio. The output
voltage supervisor manages the reset phase for
any digital load (µC, FPGA). The RST open
collector output can also implement output
voltage sequencing during the power-up phase.
The synchronous rectification, designed for high
efficiency at medium - heavy load, and the high
switching frequency capability make the size of
the application compact. Pulse by pulse current
sensing on both power elements implements an
effective constant current protection.
Applications
Designed for automotive systems
Battery powered applications
Car body applications (LCM)
Car audio and low noise applications (LNM)
April 2015
This is information on a product in full production.
DocID027738 Rev 2
1/77
www.st.com
1 page  
A6985F
2 Pin settings
2.1 Pin connection
Figure 2. Pin connection (top view)
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Pin settings
2.2 Pin description
Table 1. Pin description
No. Pin
Description
The RST open collector output is driven low when the output voltage is out of regulation. The RST
1 RST is released after an adjustable time DELAY once the output voltage is over the active delay
threshold.
2
VCC
Connect a ceramic capacitor (≥ 470 nF) to filter internal voltage reference. This pin supplies the
embedded analog circuitry.
3
SS/INH
An open collector stage can disable the device clamping this pin to GND (INH mode). An internal
current generator (2 A typ.) charges the external capacitor to implement the soft-start.
4
SYNCH/ The pin features Master / Slave synchronization in LNM (see Section 7.5 on page 47) and skip
ISKP current level selection in LCM (see Section 5.5.2 on page 26).
5
FSW
A pull up resistor (E24 series only) to VCC or pull down to GND selects the switching frequency.
Pinstrapping is active only before the soft-start phase to minimize the IC consumption.
A pull up resistor (E24 series only) to VCC or pull down to GND selects the low noise mode/low
6 MLF consumption mode and the active RST threshold. Pinstrapping is active only before the soft-start
phase to minimize the IC consumption.
7 COMP Output of the error amplifier. The designed compensation network is connected at this pin.
An external capacitor connected at this pin sets the time DELAY to assert the rising edge of the
8 DELAY RST o.c. after the output voltage is over the reset threshold. If this pin is left floating, RST is like
a Power Good.
9 VOUT Output voltage sensing
10 SGND Signal GND
DocID027738 Rev 2
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A6985F
Electrical characteristics
TJ = -40 to 135 °C, VIN = 12 V unless otherwise specified.
Table 6. fSW selection
Symbol RVCC (E24 series) RGND (E24 series) Tj fSW min. fSW typ.
0 NC 225 250
1.8 k
NC
285
3.3 k
5.6 k
NC
(1)
NC
330
380
10 k
NC
435
NC 0 450 500
18 k
NC
575
33 k
fSW 56 k
NC
(1)
NC
660
755
NC 1.8 k
870
NC 3.3 k 900 1000
NC 5.6 k
1150
NC
10 k
(1)
1310
NC 18 k
1500
NC
33 k
1575
1750
NC
56 k
1800
2000
1. Not tested in production.
fSW max.
275
550
1100
1925
2200
Unit
kHz
TJ = -40 to 135 °C, VIN = 12 V unless otherwise specified.
Symbol
RVCC
(E24 1%)
Table 7. LNM / LCM selection (A6985F3V3)
RGND
Operating VRST/VOUT
(E24 1%)
mode (tgt. value)
VRST
min.
VRST
typ.
VRST
max.
Unit
VRST
0
8.2 k
18 k
39 k
NC
NC
NC
NC
NC
NC
NC
NC
0
8.2 k
18 k
39 k
LCM
LNM
93%
80%
87%
96%
93%
80%
87%
96%
3.008
2.587
2.814
3.105
3.008
2.587
2.814
3.105
3.069
2.640
2.871
3.168
3.069
2.640
2.871
3.168
3.130
2.693
2.928
3.231
3.130
2.693
2.928
3.231
V
DocID027738 Rev 2
11/77
77
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet A6985F.PDF ] | |
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