STMICROELECTRONICS L6902D_04

L6902D
UP TO 1A SWITCHING REGULATOR WITH
ADJUSTABLE CURRENT LIMIT
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Figure 1. Package
FEATURES
UP TO 1A OUTPUT CURRENT
OPERATING INPUT VOLTAGE FROM 8V TO 36V
PRECISE 3.3V (±2%) REFERENCE VOLTAGE
5% OUTPUT CURRENT ACCURACY
OUTPUT VOLTAGE ADJUSTABLE FROM
1.235V TO 34V
250KHz INTERNALLY FIXED FREQUENCY
VOLTAGE FEEDFORWARD
ZERO LOAD CURRENT OPERATION
ADJUSTABLE CURRENT LIMIT
PROTECTION AGAINST FEEDBACK
DISCONNECTION
THERMAL SHUTDOWN
SO-8
Table 1. Order Codes
Part Number
Package
L6902D
SO-8
L6902D013TR
SO-8 in Tape & Reel
rent 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)
a current limit programming is very simple and accurate (±5%). Moreover constant current control can be
used to charge NiMH and NiCd batteries.
APPLICATIONS
CHARGERS FOR NiCd, NiMH BATTERIES
AND PREREGULATOR FOR LITHIUM-ION
BATTERIES
ADJUSTABLE CURRENT GENERATOR
SIMPLE STEP-DOWN CONVERTERS WITH
ADJUSTABLE CURRENT LIMIT
BATTERY EQUIPPED SYSTEMS
DISTRIBUTED POWER SUPPLY
MOBILE PC & SUBNOTEBOOK
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 250mΩ assures high efficiency and a minimum dropout even at high output current level. The internal limiting current (latched function) of typical value
of 2.5A protects the device from accidental output short
circuit avoiding dangerous loads damage.
DESCRIPTION
The L6902D is a complete and simple step down
switching regulator with adjustable current limit.
Based on a voltage mode structure it integrates a cur-
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.
Figure 2. Test And Application Circuit
VCC
VIN=8V to 36V
3.3V
VREF
COMP
C1
10µF
25V
CERAMIC
C3
220pF
1
8
6
2
4
L1 22µH
RSENSE
D1
STPS340U
100mΩ
VOUT=3.3V
R1
5.6K
3
C2
22nF
R3
5.1K
OUT
7
GND
5
FB
R2
3.3K
C4
100µF
10V
POSCAP
D01IN1306A
October 2004
Rev. 8
1/7
L6902D
3 DESCRIPTION (continued)
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 250KHz, and the SO-8 package pin allow to built an ultra compact DC/
DC converter with a minimum board space.
Figure 3. Pin Connection
OUT
1
8
VCC
CS+
2
7
GND
CS-
3
6
VREF
COMP
4
5
FB
Table 2. Pin Description
N°
Pin
1
OUT
Function
2
CS+
Current Error Amplifier input (current sense at higher voltage)
3
CS-
Current Error Amplifier input (current sense at lower voltage)
4
COMP
5
FB
Regular Output
E/A output to be used for frequency compensation
Stepdown feedback input. Connecting directly to this pin results in an output voltage of 1.235V.
An external resistive divider is required for higher output voltages. In this case:
V out = V FB ⋅  1 + R1
-------- = 1.235V  1 + R1
--------


R2
R2
6
VREF
3.3V VREF. No cap is need for stability.
7
GND
Ground
8
VCC
Unregulated DC input voltage.
Table 3. Thermal Data
Symbol
Rth j-amb
Parameter
Thermal Resistance Junction to Ambient Max.
Value
Unit
110 (*)
°C/W
Value
Unit
(*) Package mounted on board.
Table 4. Absolute Maximum Ratings
Symbol
V8
Input Voltage
V1
Output DC voltageOutput peak voltage at t = 0.1µs
I1
Maximum output current
40
V
-1 to 40
-5 to 40
V
V
Internally limited
V4, V5
Analog pins
4
V
V2, V3
Analog pins
-0.3V to VCC
V
0.7
W
Ptot
Tj
Tstg
2/7
Parameter
Power dissipation at Tamb ≤ 70 °C
Operating junction temperature range
-40 to 150
°C
Storage temperature range
-55 to 150
°C
L6902D
Figure 4. Internal Block Diagram
Vcc
VOLTAGES
MONITOR
3.8V
INHIBIT
1.235V
CS+
VREF
GOOD
SUPPLY
Vref
Current_E/A
+
THERMAL
SHUTDOWN
-
TRIMMING
CSCOMP
PEAK TO PEAK
CURRENT LIMITING
Voltage_E/A
VFB
1.235V
+
E/A
-
-
D
PWM
Q
+
DRIVER
CK
OSCILLATOR
OUT
FREQUENCY
SHIFTER
GND
Table 5. Electrical Characteristcs
(Tj = 25°C, VCC = 12V, unless otherwise specified.) (•) Specification Referred to Tj from 0 to 125°C.
Symbol
Parameter
Test Condition
Min.
Operating input voltage range
VO = 1.235V; IO = 1A
•
Vd
Dropout voltage
VCC = 8V; IO = 1A
•
IO
Operating charging current
Rsense = 0.1Ω
VCC
Il
Maximum limiting current
fs
Switching frequency
d
VCC = 8V to 36V
Typ.
Max.
Unit
36
V
0.25
0.5
V
1
1.05
A
1.08
A
8
0.95
•
0.92
•
2
2.5
3.2
A
•
212
250
287
kHz
225
250
275
kHz
100
%
Duty cycle
0
DYNAMIC CHARACTERISTICS
V5
η
Voltage feedback (FB)
Efficiency
8V < VCC < 36V,
20mA < IO < 1A
•
VO = 5V, VCC = 12V
1.21
1.235
1.259
V
1.198
1.235
1.272
V
90
%
DC CHARACTERISTICS
Iqop
Iq
Total operating quiescent
current
Quiescent current
•
Duty cycle = 0; VFB = 1.5V
3
5
mA
3
mA
3/7
L6902D
Table 5. Electrical Characteristcs (continued)
(Tj = 25°C, VCC = 12V, unless otherwise specified.) (•) Specification Referred to Tj from 0 to 125°C.
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
VOLTAGE ERROR AMPLIFIER
VOH
High level output voltage
VFB = 1V
VOL
Low level output voltage
VFB = 1.5
Source output current
Vcomp = 1.9V; VFB = 1V
Io sink
Sink output current
Vcomp = 1.9V; VFB = 1.5V
Ib
Source bias current
Io source
gm
3.6
V
0.4
200
300
µA
1
1.5
mA
2.5
DC open loop gain
RL = 0
Transconductance
Icomp = -0.1 to 0.1mA
Vcomp = 1.9V
V
50
4
µA
58
dB
2.3
mS
CURRENT ERROR AMPLIFIER
Voffs
Input offset voltage
VCS- = 1.8V; VCS+ = Vcomp
ICS+
CS+ Output Current
ICS-
CS- Output Current
95
100
105
mV
IO = 1A, Rsense = 100mΩ
Vout < VCC -2V
1.5
3
µA
IO = 1A, Rsense = 100mΩ
Vout < VCC -2V
1.5
3
µA
3.234
3.3
3.366
V
3.2
3.3
3.399
V
REFERENCE SECTION
Reference Voltage
IREF = 0 to 5mA
VCC = 8V to 36V
Line Regulation
IREF = 0mA
VCC = 8V to 36V
5
10
mV
Load Regulation
IREF = 0 to 5mA
8
15
mV
Short Circuit Current
4/7
•
10
mA
L6902D
Figure 5. SO-8 Mechanical Data & Package Dimensions
mm
inch
DIM.
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
1.35
1.75
0.053
0.069
A1
0.10
0.25
0.004
0.010
A2
1.10
1.65
0.043
0.065
B
0.33
0.51
0.013
0.020
C
0.19
0.25
0.007
0.010
D (1)
4.80
5.00
0.189
0.197
E
3.80
4.00
0.15
0.157
e
1.27
0.050
H
5.80
6.20
0.228
0.244
h
0.25
0.50
0.010
0.020
L
0.40
1.27
0.016
0.050
k
ddd
OUTLINE AND
MECHANICAL DATA
0˚ (min.), 8˚ (max.)
0.10
0.004
Note: (1) Dimensions D does not include mold flash, protrusions or gate burrs.
Mold flash, potrusions or gate burrs shall not exceed
0.15mm (.006inch) in total (both side).
SO-8
0016023 C
5/7
L6902D
Table 6. Revision History
6/7
Date
Revision
Description of Changes
January 2004
7
Technical Migration from ST-PRESS to EDOCS.
October 2004
8
Changed Style Look & Feel.
Changed Iq value in Table 5 page 3/7 from 2.7mA max. to 3.0mA max.
L6902D
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of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
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