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Linear Technology Electronic Components Datasheet

LTC1909-8 Datasheet

Step-Down DC/DC Controller

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LTC1909-8 pdf
LTC1909-8
Wide Operating Range,
No RSENSETM Step-Down DC/DC
Controller with SMBus Programming
FEATURES
s SMBus/I2CTM Programmable Output Voltage:
1.3V to 3.5V
s No Sense Resistor Required
s 2% to 90% Duty Cycle at 200kHz
s tON(MIN) 100ns
s True Current Mode Control
s Stable with Ceramic COUT
s Power Good Output Voltage Monitor and 50µs Timer
s Wide VIN Range: 4V to 36V (Abs Max)
s Precision Resistor Divider and Reference Provide
±1.35% Output Voltage Accuracy Over Temperature
s Adjustable Switching Frequency and Current Limit
s Forced Continuous Control Pin
s Programmable Soft-Start
s Output Overvoltage Protection
s Optional Short-Circuit Shutdown Timer
s Available in a 28-Lead SSOP Package
U
APPLICATIO S
s Power Supplies for DSPs, ASICs, FPGAs and CPUs
s Voltage Margining
DESCRIPTIO
The LTC®1909-8 is a synchronous step-down switching
regulator controller with a digitally programmable output
voltage. The output voltage is selected from one of two
5-bit settings programmed into internal registers via a
2-wire SMBus/I2C interface. The interface features safe-
guards against invalid output voltages and allows the mi-
croprocessor to turn the regulator on and off. Valley cur-
rent control delivers very low duty cycles without requiring
a sense resistor. Operating frequency is selected by an
external resistor and is compensated for variations in VIN
and VOUT.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
operation when the main output is lightly loaded.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer.
The LTC1909-8 is available in the 28-lead SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No RSENSE is a trademark of Linear Technology Corporation.
I2C is a trademark of Philips Electronics N.V.
TYPICAL APPLICATIO
100k 100k
100k
0.1µF
11k 39k
100pF
470pF
20k
SEL
SDA
SCL
VRON
LTC1909-8
1 28
RUN/SS BOOST
2
VON
3
PGOOD
27
TG
26
SW
4
VRNG
5
FCB
SENSE+ 25
24
PGND
6
ITH
7
SGND
8
ION
9
VFB
10
SEL
11
SDA
BG
INTVCC
VIN
EXTVCC
VCC
GND
23
22
21
20 5V
19 EXT
18
12
SCL
17
FB
13 16
VRON VOSENSE
14 15
PGTMR CPUON
CMDSH-3
0.22µF
1
0.1µF
RON
1.4M 1%
+
M1 L1
1.8µH
CIN
10µF
50V
×4
VIN
5V TO 24V
GND
VOUT
2.5V OR 2.6V
10A
(VOUT SET BY SEL)
M2
4.7µF
6.3V
+
COUT1, 2
180µF
COUT3
22µF
4V 6.3V
×2 X7R
D1
GND
19098 F01
CIN: UNITED CHEMICON THCR60E1H106TZ
COUT1, 2: CORNELL DUBILIER ESRE181ME04B/
PANASONIC EEFVEOG181R
D1: DIODES INC. B340A
L1: SUMIDA CEP125-1R8MC-H
M1: Si4884
M2: Si4874
Figure 1. High Efficiency Step-Down Converter
19098f
1


Linear Technology Electronic Components Datasheet

LTC1909-8 Datasheet

Step-Down DC/DC Controller

No Preview Available !

LTC1909-8 pdf
LTC1909-8
ABSOLUTE AXI U RATI GS
(Note 1)
Input Supply Voltage
VIN, ION ..................................................– 0.3V to 36V
Boosted Topside Driver Supply Voltage
BOOST .................................................. – 0.3V to 42V
SW, SENSE+ Voltages ................................. – 5V to 36V
EXTVCC, (BOOST – SW), RUN/SS, PGOOD, INTVCC,
SEL, SDA, SCL, VRON, PGTMR, VOSENSE,
FB, CPUON, VCC Voltages .......................... – 0.3V to 7V
FCB, VON, VRNG Voltages ....... – 0.3V to (INTVCC + 0.3V)
ITH, VFB Voltages...................................... – 0.3V to 2.7V
TG, BG, INTVCC, EXTVCC Peak Currents .................... 2A
TG, BG, INTVCC, EXTVCC RMS Currents .............. 50mA
Operating Ambient Temperature Range
LTC1909-8EG (Note 2) ....................... – 40°C to 85°C
Junction Temperature (Note 4) ............................ 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
RUN/SS 1
VON 2
PGOOD 3
VRNG 4
FCB 5
ITH 6
SGND 7
ION 8
VFB 9
SEL 10
SDA 11
SCL 12
VRON 13
PGTMR 14
TOP VIEW
28 BOOST
27 TG
26 SW
25 SENSE+
24 PGND
23 BG
22 INTVCC
21 VIN
20 EXTVCC
19 VCC
18 GND
17 FB
16 VOSENSE
15 CPUON
ORDER PART
NUMBER
LTC1909-8EG
G PACKAGE
28-LEAD PLASTIC SSOP
TJMAX = 125°C, θJA = 95°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS (Switching Regulator Controller) The q denotes specifications which apply
over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 15V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Main Control Loop
IQ Input DC Supply Current
Normal
Shutdown Supply Current
900 2000
15 30
µA
µA
VFB
VFB(LINEREG)
VFB(LOADREG)
IFB
gm(EA)
VFCB
IFCB
tON
Feedback Reference Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
Feedback Input Current
Error Amplifier Transconductance
Forced Continuous Threshold
Forced Continuous Pin Current
On-Time
tON(MIN)
tOFF(MIN)
VSENSE(MAX)
Minimum On-Time
Minimum Off-Time
Maximum Current Sense Threshold
VPGND – VSENSE+
VSENSE(MIN)
Minimum Current Sense Threshold
VPGND – VSENSE+
VFB(OV)
Output Overvoltage Fault Threshold
ITH = 1.2V (Note 3)
VIN = 4V to 30V, ITH = 1.2V (Note 3)
ITH = 0.5V to 1.9V (Note 3)
VFB = 0.8V
ITH = 1.2V (Note 3)
VFCB = 0.8V
ION = 60µA, VON = 1.5V
ION = 30µA, VON = 1.5V
ION = 180µA, VON = 0V
ION = 60µA, VON = 1.5V
VRNG = 1V, VFB = 0.76V
VRNG = 0V, VFB = 0.76V
VRNG = INTVCC, VFB = 0.76V
VRNG = 1V, VFB = 0.84V
VRNG = 0V, VFB = 0.84V
VRNG = INTVCC, VFB = 0.84V
q 0.792
q
q 1.4
q 0.76
212
425
113
q 79
158
5.5
0.800
0.002
– 0.05
–5
1.7
0.8
–1
250
500
50
250
133
93
186
– 67
– 47
– 93
7.5
0.808
– 0.3
±50
2
0.84
–2
288
575
100
400
153
107
214
9.5
V
%/V
%
nA
mS
V
µA
ns
ns
ns
ns
mV
mV
mV
mV
mV
mV
%
19098f
2


Part Number LTC1909-8
Description Step-Down DC/DC Controller
Maker Linear Technology
Total Page 30 Pages
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LTC1909-8 pdf
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