DC952A - Demo Manual

DEMO CIRCUIT 952
QUICK STARTLTC3810
GUIDE
LTC3810 Current Mode
Synchronous Switching
Regulator Controller
DESCRIPTION
Demonstration circuit 952 is a current mode synchronous switching regulator featuring the
LTC3810. The circuit is configured as a synchronous step-down regulator operating at 230kHz
switching frequency. Output voltage is 12V at 6A
maximum load. The input voltage range is 13V –
80V.
The operating mode can be selected with jumper
JP1. Depending on the position of this jumper, at
low load the circuit will operate in forced continuous mode (for best load transient response at low
current) or in pulse skip mode (for best efficiency
at low current). With jumper JP1 in the mid position
the circuit can synchronize to an external clock
signal on the Mode/Sync pin.
PERFORMANCE SUMMARY
SYMBOL
VIN
VOUT
IOUT
IQ
IIN
PARAMETER
Input Supply Range
Output Voltage
Output Current
Input Current In Shutdown
VIN Current In Pulse Skip Mode
(No Load)
IIN
VIN Current In Forced Continuous Mode
(No Load)
Efficiency Efficiency
A Power Good output is provided. The PGOOD
output is normally high, with a pull up resistor to
VLOGIC. If the output voltage is not within ± 10%
of nominal value the PGOOD signal will go low.
The circuit can be synchronized to an external
clock signal.
Design files for this circuit board are available.
Call the LTC factory.
L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are
registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load,
DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, µModule, Micropower
SwitcherCAD, Multimode Dimming, No Latency ∆Σ, No Latency Delta-Sigma, No
RSENSE, Operational Filter, PanelProtect, PowerPath, PowerSOT, SmartStart,
SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are
trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products.
Specifications are at TA = 25°C
CONDITIONS
VIN = 24V, ILOAD = 100mA
VIN = 24V
VIN = 24V, RUN/SS = 0V
VIN = 24V, VFCB = INTVCC, No Load
VIN = 24V, VFCB = 0V, No Load
VIN = 24V, IOUT = 6A
MIN
13
11.8
0
TYP
12
288
3.5
MAX
80
12.2
6
648
UNITS
V
V
A
µA
mA
26
mA
96.4
%
OPERATING PRINCIPLES
The LTC3810 is a synchronous step-down switching regulator controller that can directly step down
voltages from up to 100V input, making it ideal for
telecom and automotive applications.
cycles with accurate cycle-by-cycle current limit
without requiring a current sense resistor. The current limit is adjustable and the operating frequency
is selected by an external resistor.
The LTC3810 uses a constant on-time valley current control architecture to deliver very low duty
The LTC3810 has a precise (0.5%) internal reference, a 25MHz error amplifier, large gate drivers,
1
LTC3810
programmable softstart, a shutdown pin, a Sync
input and a Power Good output.
The LTC3810 has a flexible bias regulator circuit
that can be configured in many different ways to fit
the application. The 10V bias regulator can control
an external series transistor that allows the bias
voltage to be generated from the input voltage.
The demo board provides different footprints for
this external series transistor.
An internal low dropout regulator can be used to
provide the bias voltage if a 6.7V…15V voltage
source is available. For example, in Demonstration
Circuit 952 the bias voltage is generated from the
input voltage during startup and from the output
voltage during normal operation.
The demonstration circuit can be configured to use
current sense resistor by moving a couple of zero
ohm resistors to different locations.
EQUIPMENT
4 DMMs
1 DC Supply 0-80V capable of delivering at least 85W
1 Adjustable load 0-6A
QUICK START PROCEDURE
Demonstration circuit 952 is easy to set up to evaluate the performance of the LTC3810. Refer to Figure 1
for proper measurement equipment setup and follow the procedure below:
1. Place jumpers in the following positions:
JP1 Forced continuous mode operation
JP2 ON
2. With power off, connect the input power supply to Vin and GND.
3. Set the power supply to 24V and turn on the power at the input.
NOTE. Make sure that the input voltage does not exceed 80V.
4. Check for the proper output voltage. Vout = 11.8V to 12.2V.
NOTE. If there is no output, temporarily disconnect the load to make sure that the load is not set too high.
5. Once the proper output voltages are established, adjust input voltage and load within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
2
LTC3810
Figure 1. Proper Measurement Equipment Setup
3
TP3
TP11
SYNC
FORCE
CONTINUOUS
SS/TRACK
INTVCC
TP4
MODE/SYNC
TP10
R6
100K
R2
OPT
0
R3
1000pF
CSS
R17 OPT
2
3
JP1
MODE/SYNC
INTVCC
PULSE SKIP
PGOOD
VLOGIC
4
1
OPT
10K
CC4
RC2
OFF
ON
JP2
2
INTVCC
0.01uF
CC3
SHUTDOWN
R1
OPT
90.9K 1%
220pF
RFB2
1K
1%
RC
33pF
CC2
CC1
R5 OPT
INTVCC R4 0
UVIN
SDB
SGND
1%
OPT
33.2K
1%
OPT
RF
470K
VIN
R8
0
VOUT
SS_TRACK
PLL_LPF
VFB
ITH
MODE_SYNC
PGOOD
VRNG
VON
NC
NC
ION
RUV1
RUV2
RFB1
14K
CF
14
13
12
11
10
9
8
7
6
5
4
3
2
1
U1 LTC3810EG
100pF
CON
R19 OPT INTVCC
RON
274K
1%
15
16
17
18
19
20
21
22
23
24
25
26
27
28
R18 OPT
NDRV
EXTVCC
INTVCC
DRVCC
BG
BGRTN
SENSE-
NC
NC
NC
SENSE+
SW
TG
BOOST
1uF
C1
OPT
C8
R15 0
R14
OPT
R9
VIN
0
VOUT
0
R13
BG
TG
0
R24
Tuesday, February 05, 2008
DESIGNER
ENGINEER
APPROVED
CHECKED
DRAWN MI
APPROVALS
CONTRACT NO.
1uF
0
OPT
C2
0.1uF
C6
Q3
ZXMN10A07F
0.1uF
C5
1
R12
BG
TG
D2
BAS19W
1
INTVCC
3
R16
24.9K
1%
R11 OPT
R10
VIN
4
0
R21
08/22/05
DATE
4
Q5
OPT
4
Q4
OPT
R22
0.012
1%
4
VIN
Q6
OPT
4
REV
Q2
Si7852DP
R23
0.012
1%
Q1
Si7852DP
OPT
R20
1
VIN
3
VIN
3
2
ECO
VIN
+
OPT
OPT
+
VOUT
CIN4
1uF
100V
VCC
VIN
VOUT
GND
12V 6A
TP5
TP2
13V - 80V
TP7
TP6
SHEET
DC952A
FILENAME: 952A-4.DSN
DWG NO
STEP-DOWN CONVERTER
CAGE CODE
1
OF
1
REV
A
APPROVED
GND
TP1
TP8
TP9
COUT2
270uF
16V
OPT
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
0.1uF
C7
OPT
+ COUT6
COUT1
270uF +
16V
CIN6
CIN5
OPT
C3
OPT
COUT5
COUT4
10uF
16V
100V
CIN2
OPT
0.1uF
DATE
10/18/07
VIN
C4
CIN3
1uF
100V
Q8
OPT
C9
+ 68uF
3
TECHNOLOGY
D1
COUT3
10uF
B1100 16V
L1 7.7uH
100V
CIN1
+ 68uF
Q7
OPT
PROD
VIN
REVISION HISTORY
DESCRIPTION
SCH, LTC3810EG, HIGH EFFICIENCY HIGH VOLTAGE
SCALE: NONE
SIZE
TITLE
1
VIN
2
4
3
INTVCC
3
1
2
4
5
6
7
8
1
2
3
5
6
7
8
1
2
3
5
6
7
8
1
2
3
5
6
7
8
1
2
3
4
4
1
2
5
6
This circuit is proprietary to Linear Technology and s upplied
for us e with Linear Technology parts.
Customer Notice:Linear Technology has m ade a bes t effort to
des ign a circuit that m eets custom er-supplied s pecifications ;
however, it rem ains the cus tom ers responsibility to verify proper
and reliable operation in the actual application, Com ponent
s ubstitution and printed circuit board layout m ay significantly
affect circuit perform ance or reliability. Contact Linear
Applications Engineering for as sis tance.
LTC3810
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