R6902D
Up to 1 A step-down switching regulator with adjustable current limit for aerospace applications
Datasheet
-
preliminary data
SO-8
Features
General features
– Up to 1 A DC output current
– Operating input voltage from 8 V to 36 V
– Output voltage adjustable from 1.235 V to
35 V
– Precise 3.3 V (± 2%) reference voltage
– 250 kHz internally fixed frequency
– Voltage feedforward
– Zero load current operation
– Internal current limiting
– 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 subppm quality goals
– Advanced mold and frame designs for superior resilience in harsh environments
(acceleration, EMI, thermal, humidity)
– Extended screening capability on request
Applications
Aerospace applications
Adjustable current generator
Simple step-down converters with adjustable current limit
Figure 1. Application schematic
October 2014 DocID026994 Rev 1
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
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4
5
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Contents
Contents
3
R6902D
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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R6902D
1 Description
Description
The R6902D is a complete and simple step-down switching regulator with an adjustable current limit. Based on a voltage mode structure it integrates a current error amplifier to have a constant voltage and constant current control. By means of an on-board current sense resistor and the availability of the current sense pins (both compatible to Vcc and for
Cs- compatible with GND too) current limit programming is very simple and accurate.
Moreover constant current control can be used to charge NiMH and NiCd batteries. The device can be used as a standard DC/DC converter with the adjustable current limit (set by using the external sense resistor). The internal robust P-channel DMOS transistor with a typical of 250 m assures high efficiency and a minimum dropout even at a high output current level. The internal limiting current (latched function) of typical value of 2.5 A protects the device from an accidental output short-circuit avoiding dangerous loads damage. If the temperature of the chip goes higher than a fixed internal threshold (150 °C with 20 °C hysteresis), the power stage is turned off. The large ambient temperature range makes it ideal for aerospace and defense applications.
Other protections beside the thermal shutdown complete the device for a safe and reliable application: overvoltage protection, frequency foldback overcurrent protection and protection vs. feedback disconnection. The internal fixed switching frequency of 250 kHz, and the SO-8 package pin allow to built an ultra compact DC/DC converter with a minimum board space.
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Pin connection R6902D
Figure 2. Pin connection (top view)
287
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5
6
7
8
No.
1
2
3
4
Pin
OUT
CS+
CS-
COMP
FB
V
REF
GND
VCC
Table 1. Pin description
Description
Regulator output.
Current error amplifier input (current sense at higher voltage)
Current error amplifier input (current sense at lower voltage)
E/A output for frequency compensation.
Feedback input. Connecting directly to this pin results in an output voltage of 1.23 V. An external resistive divider is required for higher output voltages.
3.3 V reference voltage. No cap is need for stability.
Ground.
Unregulated DC input voltage.
4/10 DocID026994 Rev 1
R6902D Electrical data
Symbol
V
8
V
1
I
1
V
4
, V
5
V
2
, V
3
P
TOT
T
J
T
STG
Table 2. Absolute maximum ratings
Parameter
Input voltage
OUT pin DC voltage
OUT pin peak voltage at t = 0.1 s
Maximum output current
Analog pins
Analog pins
Power dissipation at T
A
70 °C
Operating junction temperature range
Storage temperature range
Value
40
-1 to 40
-5 to 40
Int. limit.
4
-0.3 to V
CC
0.7
-40 to 150
-55 to 150
Unit
V
V
V
V
V
W
°C
°C
Symbol
Table 3. Thermal data
Parameter
R thJA
Maximum thermal resistance junction ambient
1. Package mounted on board.
SO-8
110
(1)
Unit
°C/W
DocID026994 Rev 1 5/10
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Electrical characteristics R6902D
T
J
= -40 to 125 °C, V
CC
= 12 V, unless otherwise specified.
Symbol Parameter
Table 4. Electrical characteristics
Test conditions Min.
Typ.
Max. Unit
R
V
CC
DS(on) f
I
L
SW
Operating input voltage range V
0
= 1.235 V; I
0
= 2 A
MOSFET on resistance
Maximum limiting current
(1)
V
CC
= 8.5 V
V
CC
= 8.5 V, T
J
= 25 °C
Switching frequency
Duty cycle
Dynamic characteristics
V
5
Voltage feedback
Efficiency
DC characteristics
I qop
Total operating quiescent current
8 V < V
V
0
CC
= 5 V, V
< 36 V, 20 mA < I
CC
= 12 V
0
< 1 A
8
1.8
2
36
0.250
0.5
2.5
2.5
3.2
3.2
V
A
212 250 280 kHz
0 100 %
1.198 1.235 1.272
90
3 5
V
% mA
I q
Quiescent current
Error amplifier
V
OH
V
OL
I o source
I o sink
I b
High level output voltage
Low level output voltage
Source output current
Sink output current
Source bias current
DC open loop gain
Duty cycle = 0; V
V
V
V
V
FB
FB
=1 V
=1.5 V
COMP
COMP
= 1.9 V; V
= 1.9 V; V
FB
FB
FB
= 1.5 V
= 1 V
= 1.5 V
3.6
160
1 gm Transconductance
V
OFFS
I
CS+
Input offset voltage
CS+ output current
I
CS-
CS- output current
Reference section
Reference voltage
I
R
L
= 50
COMP
= -0.1 mA to 0.1 mA; V
V
CS-
= 1.8 V; V
CS+
= V comp
I
0
= 1 A; R
SENSE
= 100 m ; V
I
0
= 1 A; R
SENSE
= 100 m ; V
COMP
= 1.9 V
OUT
< V
CC
- 2 V
OUT
< V
CC
- 2 V
Line regulation
Load regulation
I
REF
= 0 to 5 mA, V
CC
= 8 V to 36 V
I
REF
= 0mA, V
CC
= 8 V to 36 V
I
REF
= 0 to 5 mA
Short-circuit current
1. With T
J
= 85 °C, I lim_min
= 2 A, assured by design, characterization and statistical correlation.
90
3.2
5
300
1.5
2.5
58
2.3
3.3
5
8
18
2.7
0.4
4
3.399
10
15
35 mA mA
A dB mS
100 110 mV
1.5
3 A
1.5
3 A
V mV mV mA
V
V
A
6/10 DocID026994 Rev 1
R6902D Package information
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK ® packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com
.
ECOPACK is an ST trademark.
DocID026994 Rev 1 7/10
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Package information
Figure 3. SO-8 package outline
R6902D
8/10
Table 5. SO-8 package mechanical data
Dimensions (mm) Dimensions (inch)
Symbol
Min.
Typ.
Max.
Min.
Typ.
Max.
H h
E e
A
A1
A2
B
C
D
(1)
L k ddd
1.35
0.10
1.10
0.33
0.19
4.80
3.80
5.80
0.25
0.40
1.27
1.75
0.25
1.65
0.51
0.25
5.00
4.00
0.053
0.004
0.043
0.013
0.007
0.189
0.15
6.20
0.50
0.228
0.010
1.27
0.016
0 ° (min), 8 ° (max)
0.10
0.050
0.244
0.020
0.050
0.004
1. 1. Dimension “D” does not include mold flash, protrusions or gate burrs. Mold flash, protrusions or gate burrs shall not exceed 0.15 mm (0.006 inch) in total (both sides).
0.069
0.010
0.065
0.020
0.010
0.197
0.157
DocID026994 Rev 1
R6902D Order codes
Order codes
R6902D
R6902D13TR
Table 6. Ordering information
Package
SO-8
Packaging
Tube
Tape and reel
Date
06-Oct-2014
Table 7. Document revision history
Revision Changes
1 Initial release.
DocID026994 Rev 1 9/10
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R6902D
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10/10 DocID026994 Rev 1
