ST A6902D User Manual
Up to 1 A step down switching regulator with adjustable
current limit for automotive applications
Features
■ Qualified following the AEC-Q100
requirements (see PPAP for more details)
■ 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
A6902D
SO-8
Applications
■ Automotive applications
■ Adjustable current generator
■ Simple step-down converters with adjustable
current limit
Figure 1. Application schematic
V
V
=8V to 36V
=8V to 36V
IN
IN
=8V to 36V
=8V to 36V
V
V
IN
IN
C1
C1
10µF
10µF
35V
35V
C3
C3
220pF
220pF
C2
C2
22nF
22nF
V
V
CC
CC
V
V
REF
REF
COMP
COMP
R3
R3
5.1kO
5.1kO
L6902D
L6902D
GND
GND
OUT
OUT
CS+
CS+
CS-
CS-
FB
FB
L1 22µH
L1 22µH
D1
D1
STPS340U
STPS340U
Rsense
Rsense
100mO
100mO
V
V
OUT
OUT
R1
R1
5.6kO
5.6kO
R2
R2
3.3kO
3.3kO
=3.3V
=3.3V
C4
C4
100µF
100µF
10V
10V
April 2009 Doc ID 13959 Rev 5 1/12
www.st.com
12
Contents A6902D
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2/12 Doc ID 13959 Rev 5
A6902D Description
1 Description
The A6902D is a complete and simple step down switching regulator with 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 Cscompatible with GND too) a 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 adjustable current limit (set by
using the external sense resistor). The internal robust P-channel DMOS transistor with a
typical of 250 mΩ assures high efficiency and a minimum dropout even at high output
current level. The internal limiting current (latched function) of typical value of 2.5 A protects
the device from 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.
Other protections beside thermal shutdown complete the device for a safe and reliable
application: overvoltage protection, frequency folback 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.
Doc ID 13959 Rev 5 3/12
Pin connection A6902D
2 Pin connection
2.1 Pin connection
Figure 2. Pin connection (top view)
2.2 Pin description
Table 1. Pin description
N° Pin Description
1 OUT Regulator output.
2 CS+ Current error amplifier input (current sense at higher voltage)
3 CS- Current error amplifier input (current sense at lower voltage)
4 COMP E/A output for frequency compensation.
Feedback input. Connecting directly to this pin results in an output
5FB
voltage of 1.23 V. An extenal resistive divider is required for higher
output voltages.
6V
REF
3.3 V reference voltage. No cap is need for stability.
7 GND Ground.
8 VCC Unregulated DC input voltage.
4/12 Doc ID 13959 Rev 5
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