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Linear Technology DC252 Demo Manual

Design-ready switcher

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DESCRIPTIO
Demonstration Circuit DC252 is designed for mobile 5-bit
VID-programmed notebook CPU applications using the
®
LTC
1736 switching regulator controller. A high perfor-
mance, constant frequency current mode architecture
generates a precise low voltage CPU core supply. Protec-
tion features include an externally defeatable overcurrent
latchoff and internal current foldback for overload condi-
tions. A soft-latched crowbar monitors the output voltage
for overvoltage protection. OPTI-LOOP
allows the transient response to be optimized over a wide
range of output capacitance and ESR values. The circuit
was designed for a 5V to 24V input range but allows a 4.5V
to 28V range (limited by the external MOSFETs). Strong
output drivers easily handle large power MOSFETs effi-
PERFOR A CE SU
PARAMETER
Input Voltage Range
Output
V
IN
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTOS
Efficiency
100
EXTV
= 5V
CC
90
V
= 5V
IN
80
70
V
= 15V
IN
V
= 24V
IN
60
50
40
10mA
100mA
1A
LOAD CURRENT (A)
Frequency Synchronous DC/DC Converter
TM
compensation
ARY
CONDITIONS
(Maximum Input Voltage Limited By External MOSFET and Input Capacitor)
Output Voltage (Programmed with a 5-Bit Mobile VID Code)
Max Output Current (Continuous)
Max Output Current (Peak)
Typical Output Ripple Measured with 10MHz Bandwidth (Burst Mode Operation) I
Typical Output Ripple Measured with 10MHz Bandwidth (Continuous) I
Line Regulation 5V to 24V
Component Side
10A
252 TA01
DEMO MANUAL DC252
DESIGN-READY SWITCHER
LTC1736 5-Bit VID Constant
ciently. Output voltages can be configured according to
Intel mobile VID standards of 0.9V to 2.0V. An internal
power-good circuit monitors the output voltage for out-of-
regulation conditions. External frequency synchronization
is provided, as are three modes of operation: Burst Mode
operation to reduce switching losses and maintain high
operating efficiencies, burst inhibit/forced continuous
mode and a low noise pulse-skipping mode that provides
constant frequency operation down to 1% maximum load
currents with low quiescent current. This results in a
power supply that has very high efficiency, low ripple and
fast transient response. Gerber files for this circuit board
are available. Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation.
= 5A
O
VALUE
5V to 24V
0.9V to 2.0V
11.0A
12A
= 100mA
45mV
O
20mV
0.002%/V
Solder Side
1
TM
P-P
P-P

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Summary of Contents for Linear Technology DC252

  • Page 1 28V range (limited by the external MOSFETs). Strong are available. Call the LTC factory. output drivers easily handle large power MOSFETs effi- , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation. PERFOR A CE SU...
  • Page 2 DEMO MANUAL DC252 DESIGN-READY SWITCHER PERFOR A CE SU PARAMETER CONDITIONS VALUE Load Regulation: No Load to Full Rated Output – 0.3% Supply Current (Typical), No Load, V = 15V, FCB = INTV 950µA Supply Current in Shutdown (Typical), V = 15V 15µA...
  • Page 3: Parts List

    DEMO MANUAL DC252 DESIGN-READY SWITCHER PARTS LIST REFERENCE QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE C1, C3 08055A470JAT1A 47pF 50V 5% NPO Capacitor (843) 946-0362 TACR475M010R 4.7µF 10V 20% Tantalum Capacitor (207) 282-5111 0805ZC105MAT1A 1µF 10V 20% X7R Capacitor (843) 946-0362...
  • Page 4: Quick Start Guide

    DEMO MANUAL DC252 DESIGN-READY SWITCHER QUICK START GUIDE This demonstration board is easy to set up to evaluate • If an external 5V supply is used, connect it to EXTV the performance of the LTC1736. Please follow the • Set the jumper JP1 so that FCB selects the desired procedure outlined below for proper operation.
  • Page 5 DEMO MANUAL DC252 DESIGN-READY SWITCHER OPERATIO The operating frequency is set by an external capacitor, as a precision resistor voltage divider sets the output , allowing maximum flexibility in optimizing effi- voltage in 50mV/25mV increments according to Table 1. OSC1 ciency.
  • Page 6 DEMO MANUAL DC252 DESIGN-READY SWITCHER OPERATIO The VID codes (00000-11110) are engineered to be com- sure the maximum voltage on PGOOD is less than 7V. ® patible with Intel Mobile Pentium II Processor specifica- During shutdown, the PGOOD output is pulled low.
  • Page 7 0.8V threshold, the controller operates in the The DC252 demo board has various modification provi- forced continuous operating mode for as long as it takes sions. Additional pad locations are available for adding to bring the secondary voltage above the 0.8V + hysteresis...
  • Page 8 DEMO MANUAL DC252 DESIGN-READY SWITCHER OPERATIO The output capacitors are generally determined by ESR cycle the run pin to start. Refer to the LTC1736 data sheet (effective series resistance) and voltage rating rather than for details. capacitance. The ESR must be small enough that output...
  • Page 9 DEMO MANUAL DC252 DESIGN-READY SWITCHER OPERATIO 100mV/ 100mV/ 5A/DIV 5A/DIV PGOOD PGOOD 5V/DIV 5V/DIV 252 F03a 252 F03b Figure 3a. Dynamic VID Change, Burst Mode Operation Defeated Figure 3b. Dynamic VID Change, Burst Mode Operation Enabled testing, the active load should be initially programmed to voltage rises above 0.1V to 0.8V.
  • Page 10 DEMO MANUAL DC252 DESIGN-READY SWITCHER OPERATIO the otherwise low ESR OS-CON. The I OPTI-LOOP LOOP compensation allows the transient response to be compensation components shown in Figure 1’s circuit will optimized over a wide range of output capacitances and provide an adequate starting point for most applications.
  • Page 11 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
  • Page 12 E E E 0.045 10 PLCS 0.035 0.025 0.020 252 PC Fab Dwg Linear Technology Corporation dc252f LT/TP 1199 500 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear-tech.com © LINEAR TECHNOLOGY CORPORATION 1999...