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LTC1736IG#PBF

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1
LTC1736
5-Bit Adjustable
High Efficiency Synchronous
Step-Down Switching Regulator
Figure 1. High Efficiency Step-Down Converter
■
Dual N-Channel MOSFET Synchronous Drive
■
Synchronizable/Programmable Fixed Frequency
■
Wide V
IN
Range: 3.5V to 36V Operation
■
5-Bit Digital-to-Analog V
OUT
Selection:
0.925V to 2.00V Range with 50mV/25mV Steps
■
OPTI-LOOP
TM
Compensation Minimizes C
OUT
■
±
1% Output Voltage Accuracy
■
Power Good Output Voltage Monitor
■
Active Voltage Positioning Compatible
■
Output Overvoltage Crowbar Protection
■
Internal Current Foldback
■
Latched Short-Circuit Shutdown Timer
with Defeat Option
■
Forced Continuous Control Pin
■
Optional Programmable Soft-Start
■
Remote Output Voltage Sense
■
Available in 24-Lead SSOP Package
■
Notebook and Palmtop Computers, PDAs
■
Power Supply for Mobile Pentium
®
II and
Pentium III Processors
■
Low Voltage Power Supplies
The LTC
®
1736 is a synchronous step-down switching
regulator controller optimized for CPU power. The output
voltage is programmed by a 5-bit digital-to-analog con-
verter (DAC) that adjusts the output voltage from 0.925V
to 2.00V according to Intel mobile VID specifications. The
0.8V reference is compatible with future microprocessor
generations.
The operating frequency (synchronizable up to 500kHz) is
set by an external capacitor allowing maximum flexibility
in optimizing efficiency. The output voltage is monitored by
a power good window comparator that indicates when the
output is within 7.5% of its programmed value.
Protection features include: internal foldback current lim-
iting, output overvoltage crowbar and optional short-cir-
cuit shutdown. Soft-start is provided by an external capaci-
tor that can be used to properly sequence supplies. The
operating current level is user-programmable via an exter-
nal current sense resistor. Wide input supply range allows
operation from 3.5V to 30V (36V maximum).
Pin defeatable Burst Mode
TM
operation provides high effi-
ciency at low load currents. OPTI-LOOP compensation
allows the transient response to be optimized over a wide
range of output capacitance and ESR values.
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP and Burst Mode are trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
V
OSENSE
I
TH
47pF
C
C1
330pF
C
B
0.22µF
D
B
CMDSH-3
V
IN
5V TO 24V
C
OSC
47pF
RUN/SS
PGND
BG
1000pF
BOOST
SW
VIDV
CC
INTV
CC
4.7µF
M2
FDS6680A
×2
M1
FDS6680A
C
OUT
: PANASONIC EEFUEOG181R
C
IN
: MARCON THCR70EIH226ZT
L1: PANASONIC ETQP6RZIR20HFA
R
SENSE
: IRC LRF2010-01-R004J
D1
MBRS340T3
1736 F01
C
SS
0.1µF
C
C2
47pF
C
OSC
R
C
33k
R
SENSE
0.004Ω
PGOOD
VID4
VID3
VID2
VID1
VID0
SGND
SENSE
–
LTC1736
SENSE
+
TG
V
IN
+
C
OUT
180µF/4V
×4
C
IN
22µF/50V
×2
CERAMIC
V
OUT
1.35V TO 1.60V
12A
+
L1
1.2µH
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC1736
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
Input Supply Voltage (V
IN
).........................36V to –0.3V
Topside Driver Supply Voltage (BOOST)....42V to –0.3V
Switch Voltage (SW) ....................................36V to –5V
EXTV
CC
, VIDV
CC
, (BOOST – SW) Voltages ..7V to –0.3V
SENSE
+
, SENSE
–
..........................1.1(INTV
CC
) to –0.3V
FCB Voltage ............................(INTV
CC
+ 0.3V) to –0.3V
I
TH
, V
OSENSE
, V
FB
Voltage .........................2.7V to –0.3V
RUN/SS, VID0 to VID4, PGOOD Voltages ....7V to –0.3V
Peak Driver Output Current <10µs (TG, BG) .............. 3A
INTV
CC
Output Current ......................................... 50mA
Operating Ambient Temperature Range
LTC1736C ............................................... 0°C to 85°C
LTC1736I............................................ –40°C to 85°C
Junction Temperature (Note 2)............................. 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C
ORDER PART
NUMBER
Consult factory for Military grade parts.
T
JMAX
= 125°C, θ
JA
= 110°C/W
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
G PACKAGE
24-LEAD PLASTIC SSOP
24
23
22
21
20
19
18
17
16
15
14
13
C
OSC
RUN/SS
I
TH
FCB
SGND
PGOOD
SENSE
–
SENSE
+
V
FB
V
OSENSE
VID0
VID1
TG
BOOST
SW
V
IN
INTV
CC
BG
PGND
EXTV
CC
VIDV
CC
VID4
VID3
VID2
ELECTRICAL CHARACTERISTICS
LTC1736CG
LTC1736IG
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop
V
OSENSE
Output Voltage Set Accuracy (Note 3) See Table 1 ● 1%
∆V
LINEREG
Reference Voltage Line Regulation V
IN
= 3.6V to 30V (Note 3) 0.001 0.02 %/V
∆V
LOADREG
Output Voltage Load Regulation (Note 3)
Measured in Servo Loop; V
ITH
= 0.7V ● 0.1 0.3 %
Measured in Servo Loop; V
ITH
= 2V ● –0.1 –0.3 %
g
m
Transconductance Amplifier g
m
1.3 mmho
V
FCB
Forced Continuous Threshold ● 0.76 0.8 0.84 V
I
FCB
Forced Continuous Current V
FCB
= 0.85V – 0.17 –0.3 µA
V
OVL
Feedback Overvoltage Lockout ● 0.84 0.86 0.88 V
I
Q
Input DC Supply Current (Note 4)
Normal Mode 450 µA
Shutdown V
RUN/SS
= 0V 15 25 µA
V
RUN/SS
Run Pin Start Threshold V
RUN/SS
, Ramping Positive 1.0 1.5 1.9 V
V
RUN/SS
Run Pin Begin Latchoff Threshold V
RUN/SS
, Ramping Positive 4.1 4.5 V
I
RUN/SS
Soft-Start Charge Current V
RUN/SS
= 0V –0.7 –1.2 µA
I
SCL
RUN/SS Discharge Current Soft Short Condition, V
FB
= 0.5V, 0.5 2 4 µA
V
RUN/SS
= 4.5V
UVLO Undervoltage Lockout Measured at V
IN
Pin (V
IN
Ramping Down) ● 3.5 3.9 V
∆V
SENSE(MAX)
Maximum Current Sense Threshold V
FB
= 0.7V ● 60 75 85 mV
I
SENSE
SENSE Pins Total Source Current V
SENSE
–
= V
SENSE
+
= 0.8V 60 80 µA
t
ON(MIN)
Minimum On-Time Tested with a Square Wave (Note 8) 160 200 ns
TG Transition Time: (Note 9)
TG t
r
Rise Time C
LOAD
= 3300pF 50 90 ns
TG t
f
Fall Time C
LOAD
= 3300pF 50 90 ns
3
LTC1736
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN/SS
= 5V unless otherwise noted.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1736CG, LTC1736IG: T
J
= T
A
+ (P
D
• 110°C/W)
Note 3: The LTC1736 is tested in a feedback loop that servos V
FB
to the
balance point for the error amplifier (V
ITH
= 1.2V).
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5: Oscillator frequency is tested by measuring the C
OSC
charge
current (I
OSC
) and applying the formula:
Note 6: With all five VID inputs floating (or tied to VIDV
CC
) the VIDV
CC
current is typically <1µA. However, the VIDV
CC
current will rise and be
approximately equal to the number of grounded VID input pins times
(VIDV
CC
– 0.6V)/40k. (See the Applications Information section for more
detail.)
Note 7: Each built-in pull-up resistor attached to the VID inputs also has a
series diode to allow input voltages higher than the VIDV
CC
supply without
damage or clamping. (See the Applications Information section for more
detail.)
Note 8: The minimum on-time condition corresponds to the on inductor
peak-to-peak ripple current ≥40% of I
MAX
(see minimum on-time
considerations in the Applications Information section).
Note 9: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
f
CpF I I
OSC
OSC CHG DIS
=
+
+
8 477 10
11
11
11
1
.( )
()
–
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
BG Transition Time: (Note 9)
BG t
r
Rise Time C
LOAD
= 3300pF 50 90 ns
BG t
f
Fall Time C
LOAD
= 3300pF 40 80 ns
TG/BG T1D Top Gate Off to Synchronous C
LOAD
= 3300pF Each Driver 100 ns
Gate-On Delay Time
TG/BG T2D Synchronous Gate Off to Top C
LOAD
= 3300pF Each Driver 70 ns
Gate-On Delay Time
Internal V
CC
Regulator
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 30V, V
EXTVCC
= 4V 5.0 5.2 5.4 V
V
LDO(INT)
Internal V
CC
Load Regulation I
CC
= 0mA to 20mA, V
EXTVCC
= 4V 0.2 1 %
V
LDO(EXT)
EXTV
CC
Drop Voltage I
CC
= 20mA, V
EXTVCC
= 5V 130 200 mV
V
EXTVCC
EXTV
CC
Switchover Voltage I
CC
= 20mA, EXTV
CC
Ramping Positive ● 4.5 4.7 V
V
EXTVCC(HYS)
EXTV
CC
Hysteresis 0.2 V
Oscillator
f
OSC
Oscillator Frequency (Note 5), C
OSC
= 43pF 265 300 335 kHz
f
H
/f
OSC
Maximum Sync Frequency Ratio 1.3
f
FCB(SYNC)
FCB Pin Threshold For Sync Ramping Negative 0.9 1.2 V
PGOOD Output
V
PGL
PGOOD Voltage Low I
PGOOD
= 2mA 110 200 mV
I
PGOOD
PGOOD Leakage Current V
PGOOD
= 5V ±1 µA
V
PG
PGOOD Trip Level V
OSENSE
with Respect to Set Output Voltage
V
OSENSE
Ramping Negative –6.0 –7.5 –9.5 %
V
OSENSE
Ramping Positive 6.0 7.5 9.5 %
VID Control
VIDV
CC
VID Operating Supply Voltage 2.7 5.5 V
I
VIDVCC
VID Supply Current (Note 6) VIDV
CC
= 3.3V 0.01 5 µA
R
VFB/VOSENSE
Resistance Between V
OSENSE
and V
FB
10 kΩ
R
RATIO
Resistor Ratio Accuracy Programmed from 0.925V to 2.00V ±0.05 %
R
PULL-UP
VID0 to VID4 Pull-Up Resistance (Note 7) V
DIODE
= 0.6V 40 kΩ
V
IDT
VID Input Voltage Threshold 0.4 1.0 1.6 V
I
VIDLEAK
VID Input Leakage Current (Note 7) VIDV
CC
< VID < 7V 0.01 ±1 µA
V
PULL-UP
VID Pull-Up Voltage VIDV
CC
= 3.3V 2.8 V
VIDV
CC
= 5V 4.5 V
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LTC1736IG#PBF

Mfr. #:
Buy LTC1736IG#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 5-B Adj Hi Eff Sync Buck Sw Reg
Lifecycle:
New from this manufacturer.
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