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STMicroelectronics Electronic Components Datasheet

L6984A Datasheet

synchronous step-down switching regulator

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L6984
36 V 400 mA synchronous step-down switching regulator
Datasheet - production data
VFDFPN10 4 x 4 x 1.0 mm
VDFPN10 3 x 3 x 1.0 mm
Features
400 mA DC output current
4.5 V to 36 V operating input voltage
Synchronous rectification
Low consumption mode or low noise mode
100 µA IQ at light load (LCM VOUT = 3.3 V)
13 µA IQ-SHTDWN
Adjustable fSW (250 kHz - 600 kHz)
Output voltage adjustable from 0.9 V
No resistor divider required for 3.3 V VOUT
VBIAS maximizes efficiency at light load
350 mA valley current limit
Constant on-time control scheme
PGOOD open collector
Thermal shutdown
Application
Automotive systems (LCM)
Battery powered applications (LCM)
Car audio and low noise applications (LNM)
Sensors (LNM)
E- metering
Description
The L6984 is a step-down monolithic switching
regulator able to deliver up to 400 mA DC. The
output voltage adjustability ranges from 0.9 V. The
fixed 3.3 V VOUT requires no external resistor
divider. 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 almost constant over the load current
range, serving low noise application specification
like car audio/sensors. The PGOOD open
collector output can 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 low-side power element implements
an effective constant current protection.
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Figure 1. Application schematic
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July 2014
This is information on a product in full production.
DocID025378 Rev 3
1/34
www.st.com


STMicroelectronics Electronic Components Datasheet

L6984A Datasheet

synchronous step-down switching regulator

No Preview Available !

Contents
Contents
L6984
1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 ESD protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 Output voltage adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Leading network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 Control loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3 Soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4 Light load operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4.1
3.4.2
Low noise mode (LNM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Low consumption mode (LCM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.5 Switchover feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.5.1
3.5.2
LCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
LNM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.6 Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.7 PGOOD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.8 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.9 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4 Design of the power components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1 Input capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.3 Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.3.1 Output voltage ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.3.2 COUT specification and loop stability . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2/34 DocID025378 Rev 3


Part Number L6984A
Description synchronous step-down switching regulator
Maker STMicroelectronics
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L6984A Datasheet PDF






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