LT1374CR-5 Linear Technology, LT1374CR-5 Datasheet
LT1374CR-5
Specifications of LT1374CR-5
Available stocks
Related parts for LT1374CR-5
LT1374CR-5 Summary of contents
Page 1
... A shutdown signal reduces supply current to 20µA. Synchro- nization allows an external logic level signal to increase the internal oscillator from 580kHz to 1MHz. , LTC and LT are registered trademarks of Linear Technology Corporation. Protected by U.S. Patents, Including 6111439, 5668493, 5656965 D2 CMDSH3 OR FMMD914 C2 0.27µ ...
Page 2
... BOOST TAB 5 V LT1374CR GND GND 3 V LT1374CR-SYNC SW 2 SYNC OR SHDN* LT1374CR-5 SYNC PACKAGE LT1374HVCR 7-LEAD PLASTIC DD LT1374IR T = 125°C, θ = 30°C/ W JMAX JA LT1374IR-5 WITH PACKAGE SOLDERED TO 0.5 SQUARE INCH COPPER AREA OVER BACKSIDE GROUND PLANE LT1374IR-SYNC OR INTERNAL POWER PLANE. θ ...
Page 3
ELECTRICAL CHARACTERISTICS ture range, otherwise specifications are at T PARAMETER Feedback Voltage (Adjustable) Sense Voltage (Fixed 5V) SENSE Pin Resistance Reference Voltage Line Regulation Feedback Input Bias Current Error Amplifier Voltage Gain Error Amplifier Transconductance V Pin to Switch Current ...
Page 4
LT1374 ELECTRICAL CHARACTERISTICS Note 5: Boost current is the current flowing into the boost pin with the pin held 5V above input voltage. It flows only during switch on time. Note 6: V supply current is the current drawn when ...
Page 5
W U TYPICAL PERFOR A CE CHARACTERISTICS Shutdown Supply Current 25V 10V 0.1 0.2 0.3 0.4 SHUTDOWN VOLTAGE (V) 1374 G07 Frequency Foldback 500 400 ...
Page 6
LT1374 W U TYPICAL PERFOR A CE CHARACTERISTICS BOOST Pin Current 100 DUTY CYCLE = 100 SWITCH CURRENT (A) 1374 G16 ...
Page 7
CTIO S SYNC: (Excludes T7 package) The sync pin is used to synchronize the internal oscillator to an external signal directly logic compatible and can be driven with any signal between 10% and ...
Page 8
LT1374 W BLOCK DIAGRA INPUT 2.9V BIAS BIAS* REGULATOR SYNC SHUTDOWN COMPARATOR – + 0.4V SHDN 3.5µA + – LOCKOUT COMPARATOR 2.38V *BIAS PIN IS AVAILABLE ONLY ON THE S0-8 AND FE16 PACKAGES U U APPLICATIO S I FOR ATIO ...
Page 9
U U APPLICATIONS INFORMATION More Than Just Voltage Feedback The feedback pin is used for more than just output voltage sensing. It also reduces switching frequency and current limit when output voltage is very low (see the Frequency Foldback graph ...
Page 10
LT1374 U U APPLICATIONS INFORMATION MAXIMUM OUTPUT LOAD CURRENT Maximum load current for a buck converter is limited by the maximum switch current rating (I This current rating is 4. 50% duty cycle (DC), decreasing to 3.7A at ...
Page 11
U U APPLICATIONS INFORMATION When choosing an inductor you might have to consider maximum load current, core and copper losses, allowable component height, output voltage ripple, EMI, fault cur- rent in the inductor, saturation, and of course, cost. The following ...
Page 12
... ESL before ESR becomes effective. They are appropriate for input bypassing because of their high ripple current ratings and tolerance of turn-on surges. Linear Technology plans to issue a design note on the use of ceramic capacitors in the near future. OUTPUT RIPPLE VOLTAGE ...
Page 13
U U APPLICATIONS INFORMATION For high frequency switchers, the sum of ripple current slew rates may also be relevant and can be calculated from: Peak-to-peak output ripple voltage is the sum of a triwave created by peak-to-peak ripple current times ...
Page 14
LT1374 U U APPLICATIONS INFORMATION that it can be recharged fully under the worst-case condi- tion of minimum input voltage. Almost any type of film or ceramic capacitor will work fine. WARNING! Peak voltage on the BOOST pin is the ...
Page 15
U U APPLICATIONS INFORMATION Threshold voltage for lockout is about 2.38V, slightly less than the internal 2.42V reference voltage. A 3.5µA bias current flows out of the pin at threshold. This internally generated current is used to force a default ...
Page 16
LT1374 U U APPLICATIONS INFORMATION V IN GND CONNECT TO PLACE FEEDTHROUGHS GROUND PLANE AROUND GND PIN FOR GOOD THERMAL CONDUCTIVITY KEEP FB AND V COMPONENTS C AWAY FROM HIGH FREQUENCY, HIGH CURRENT COMPONENTS Figure 5a. Suggested Layout (Topside Only ...
Page 17
U U APPLICATIONS INFORMATION KEEP FB AND V C COMPONENTS AWAY FROM HIGH FREQUENCY, HIGH CURRENT COMPONENTS KELVIN SENSE OUTPUT D2 Figure 5b. Suggested Layout (Topside Only Shown) TSSOP W U SOLDER EXPOSED PAD AND USE FEEDTHROUGHS FOR BETTER THERMAL ...
Page 18
LT1374 U U APPLICATIONS INFORMATION V IN PLACE FEEDTHROUGHS V D2 OUT AROUND GND TAB, C3, D1 FOR GOOD THERMAL C4 CONDUCTIVITY KELVIN SENSE R2 V OUT MINIMIZE LT1374 C3, D1 LOOP CONNECT TO GND PLANE C3 ...
Page 19
U U APPLICATIONS INFORMATION PARASITIC RESONANCE Resonance or “ringing” may sometimes be seen on the switch node (see Figure 7). Very high frequency ringing following switch rise time is caused by switch/diode/input capacitor lead inductance and diode capacitance. Schot- tky ...
Page 20
LT1374 U U APPLICATIONS INFORMATION The term inside the radical has a maximum value of 0.5 when input voltage is twice output, and stays near 0.5 for a relatively wide range of input voltages common practice therefore to ...
Page 21
U U APPLICATIONS INFORMATION THERMAL CALCULATIONS Power dissipation in the LT1374 chip comes from four sources: switch DC loss, switch AC loss, boost circuit current, and input quiescent current. The following formu- las show how to calculate each of these ...
Page 22
LT1374 U U APPLICATIONS INFORMATION Error amplifier transconductance phase and gain are shown in Figure 11. The error amplifier can be modeled as a transconductance of 2000µMho, with an output impedance of 200kΩ in parallel with 12pF. In all practical ...
Page 23
U U APPLICATIONS INFORMATION What About a Resistor in the Compensation Network common practice in switching regulator design to add a “zero” to the error amplifier compensation to increase loop phase margin. This zero is created in the ...
Page 24
LT1374 U U APPLICATIONS INFORMATION current and ripple current variations), output capacitance (±20% to ±50% due to production tolerance, tempera- ture, aging and changes at the load), output capacitor ESR (±200% due to production tolerance, temperature and aging), and finally, ...
Page 25
U U APPLICATIONS INFORMATION likely to be changed in production is the output capacitor, because that is the component most likely to have manu- facturer variations (in ESR) large enough to cause prob- lems. It would be a wise move ...
Page 26
LT1374 U U APPLICATIONS INFORMATION With the conditions above: This duty cycle is close enough to 50% that I assumed to be 4.5A. OUTPUT DIVIDER If the adjustable part is used, the resistor connected to V (R2) should be set ...
Page 27
U U APPLICATIONS INFORMATION This says that discontinuous mode can be used and the minimum inductor needed is found from: In practice, the inductor should be increased by about 30% over the calculated minimum to handle losses and varia- tions ...
Page 28
LT1374 U U APPLICATIONS INFORMATION 6.60 ±0.10 4.50 ±0.10 SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN ...
Page 29
PACKAGE DESCRIPTION .060 .256 (1.524) (6.502) .060 .183 (1.524) (4.648) .075 (1.905) .300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK .420 .050 RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING ...
Page 30
LT1374 PACKAGE DESCRIPTION .050 BSC .245 MIN .030 ±.005 TYP RECOMMENDED SOLDER PAD LAYOUT .010 – .020 (0.254 – 0.508) .008 – .010 (0.203 – 0.254) NOTE: 1. DIMENSIONS IN 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT ...
Page 31
... BSC (1.27) 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 Package 7-Lead Plastic TO-220 (Standard) (LTC DWG # 05-08-1422) .147 – ...
Page 32
... High Efficiency Step-Down Converter LT1765 3A Step-Down Switching Regulator LT1766 1.5A Step-Down Switching Regulator LT1767 1.5A Step-Down Switching Regulator Burst Mode is a registered trademark of Linear Technology Corporation. Linear Technology Corporation 32 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● losses. C4 provides a low impedance path to maintain an equal voltage swing in L1B, improving regulation flyback converter, during switch on time, all the converter’ ...