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PDF R5975D Data sheet ( Hoja de datos )
| Número de pieza | R5975D | |
| Descripción | Up to 3A step-down switching regulator | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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R5975D
Up to 3 A step-down switching regulator for aerospace applications
HSOP8 - exposed pad
Features
General features
– 3 A DC output current
– Operating input voltage from 4 V to 36 V
– 3.3 V / (± 2%) reference voltage
– Large ambient temperature range:
-40 °C to 125 °C
– Output voltage adjustable from 1.235 V to
35 V
– Low dropout operation: 100% duty cycle
– 250 kHz internally fixed frequency
– Voltage feed-forward
– Zero load current operation
– Internal current limiting
– Inhibit for zero current consumption
– Synchronization
– Protection against feedback disconnection
– Thermal shutdown
Aerospace and defense features
– Suitable for use in aerospace and defense
applications
– Dedicated traceability and part marking
– Production parts approval documents
available
– Adapted extended life time and
obsolescence management
– Extended product change notification
process
– Designed and manufactured to meet sub-
ppm quality goals
– Advanced mold and frame designs for
superior resilience in harsh environments
(acceleration, EMI, thermal, humidity)
– Extended screening capability on request
Datasheet - preliminary data
Applications
Dedicated to aerospace applications
Description
The R5975D is a step-down monolithic power
switching regulator with a minimum switch current
limit of 3.75 A, it is therefore able to deliver up to
3 A DC current to the load depending on the
application conditions. The output voltage can be
set from 1.235 V to 35 V. The high current level is
also achieved thanks to a HSOP8 package with
exposed frame, that allows to reduce the RTHJ-A
down to approximately 40 °C/W. The device uses
an internal P-channel DMOS transistor (with
a typical RDS(on) of 250 mΩ) as switching element
to minimize the size of the external components.
An internal oscillator fixes the switching frequency
at 250 kHz. The large ambient temperature range
makes it ideal for aerospace and defense
applications. Pulse-by-pulse current limit with the
internal frequency modulation offers an effective
constant current short-circuit protection.
October 2014
DocID026878 Rev 1
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to
change without notice.
1/47
www.st.com
1 page  
R5975D
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Internal circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Oscillator circuit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Synchronization example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Current limitation circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Driving circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Block diagram of the loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Error amplifier equivalent circuit and compensation network . . . . . . . . . . . . . . . . . . . . . . . 20
Module plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Phase plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Layout example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Switching losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Power losses estimation (VIN = 5 V, fSW = 250 kHz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Power loss estimation (VIN = 12 V, fSW = 250 kHz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Measurement of the thermal impedance of the demonstration board . . . . . . . . . . . . . . . . 31
Maximum continuous output current vs. duty cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Short-circuit current VIN = 12 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Short-circuit current VIN = 24 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Short-circuit current VIN = 36 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Positive buck-boost regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Negative buck-boost regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Floating boost topology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
350 mA LED boost current source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Synchronization example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
MLCC compensation network circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Soft-start network example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Line regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Shutdown current vs. junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Output voltage vs. junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Switching frequency vs. junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Quiescent current vs. junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Junction temperature vs. output current (VIN 5 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Junction temperature vs. output current (VIN 12 V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Efficiency vs. output current (VIN 12 V). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Efficiency vs. output current (VIN 5 V). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
HSOP8 package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
DocID026878 Rev 1
5/47
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5 Page 
R5975D
5 Functional description
Functional description
The main internal blocks are shown in the device block diagram in Figure 2. They are:
A voltage regulator supplying the internal circuitry. From this regulator, a 3.3 V
reference voltage is externally available
A voltage monitor circuit which checks the input and the internal voltages
A fully integrated sawtooth oscillator with a frequency of 250 kHz 15%, including also
the voltage feed-forward function and an input/output synchronization pin
Two embedded current limitation circuits which control the current that flows through
the power switch. The pulse-by-pulse current limit forces the power switch OFF cycle-
by-cycle, if the current reaches an internal threshold, while the frequency shifter
reduces the switching frequency in order to significantly reduce the duty cycle
A transconductance error amplifier
A pulse width modulator (PWM) comparator and the relative logic circuitry necessary to
drive the internal power
A high side driver for the internal P-MOS switch
An inhibit block for standby operation
A circuit to implement the thermal protection function
Figure 2. Block diagram
DocID026878 Rev 1
$0 Y
11/47
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet R5975D.PDF ] | |
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