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PDF LTC1909-8 Data sheet ( Hoja de datos )
| Número de pieza | LTC1909-8 | |
| Descripción | Step-Down DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC1909-8 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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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
1Ω
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
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
Transient Response
Transient Response
(Discontinuous Mode)
VOUT
50mV/DIV
VOUT
50mV/DIV
IL
5A/DIV
IL
5A/DIV
20µs
LOAD STEP 0A TO 10A
VIN = 15V
VOUT = 2.5V
FCB = 0V
FIGURE 1 CIRCUIT
19098 G16
Efficiency vs Input Voltage
100
FCB = 5V
FIGURE 1 CIRCUIT
95
ILOAD = 1A
90
ILOAD = 10A
85
80
0
5 10 15 20 25
INPUT VOLTAGE (V)
30
19098 G19
ITH Voltage vs Load Current
2.5
FIGURE 1 CIRCUIT
2.0
1.5
CONTINUOUS
MODE
1.0
DISCONTINUOUS
0.5 MODE
0
0 5 10 15
LOAD CURRENT (A)
19098 G22
20µs
LOAD STEP 1A TO 10A
VIN = 15V
VOUT = 2.5V
FCB = INTVCC
FIGURE 1 CIRCUIT
19098 G17
Frequency vs Input Voltage
300
FCB = 0V
FIGURE 1 CIRCUIT
280
IOUT = 10A
260
240 IOUT = 0A
220
200
5
10 15 20
INPUT VOLTAGE (V)
25
19098 G20
Current Sense Threshold
vs ITH Voltage
300
VRNG = 2V
200 1.4V
1V
100 0.7V
0.5V
0
–100
–200
0
0.5 1.0 1.5 2.0
ITH VOLTAGE (V)
2.5 3.0
19098 G23
LTC1909-8
Efficiency vs Load Current
100
90
DISCONTINUOUS
MODE
80
CONTINUOUS
MODE
70
60
50
0.001
VIN = 10V
VOUT = 2.5V
EXTVCC = 5V
FIGURE 1 CIRCUIT
0.01 0.1
1
LOAD CURRENT (A)
10
19098 G18
Load Regulation
0
FIGURE 1 CIRCUIT
–0.1
–0.2
–0.3
–0.4
0
2 4 68
LOAD CURRENT (A)
10
19098 G21
Current Limit Foldback
150
125
100
75
50
25
0
0 0.2 0.4 0.6 0.8
VFB (V)
1778 G09
19098f
5
5 Page 
W
FU CTIO AL DIAGRA
LTC1909-8
RON
2 VON 8 ION
SMBON*
0.7V 2.4V
DCON*
PGTMR* 14
50µs
TIMER*
5 FCB
1µA
4.7V
+
1
OST
tON
=
VVON
IION
(10pF)
+
ICMP
–
20k
R
SQ
0.8V
–+
F
+
IREV
–
1.4V
VRNG
4
0.7V
×
3.3µA
1
240k
ITHB
Q2 Q4
Q6
1V
20 EXTVCC
–
21 VIN
+
CIN
0.8V
REF
5V
REG
VIN
FCNT
ON
SWITCH
LOGIC
SHDN
OV
BOOST
28
TG
27
SW
26
SENSE+
25
INTVCC
22
BG
23
PGND
24
PGOOD
3
+
UV
–
0.76V
CB
M1
L1
DB
CVCC
VOSENSE*
16
M2
+ VOUT
COUT
RFB1*
VFB FB*
9 17
POR*
SGND GND*
7 18
VCC*
19
RFB2*
SEL*
+ 10
– 1.3V
Q3 Q1
+– 0.8V
×4 EA
0.8V
Q5
SS
–+
0.6V
6 ITH RC CC1
RUN
SHDN
+
OV
–
1.2µA
6V
0.6V CSS 1 RUN/SS
10:5
MUX*
REGISTER 0*
REGISTER 1*
SCL*
12
0.84V
*
DCON*
* SMBON*
*
ON/OFF
STATE
MACHINE*
SMBus
INTERFACE*
SDA*
11
VCC*
15 CPUON*
*
VRON*
+ 13
*PART OF THE SMBus VID PROGRAMMER
– 1.3V
19098 FD
19098f
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC1909-8.PDF ] | |
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