Datasheet

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LT1619

1619fa

Low Voltage Current Mode

PWM Controller

, LTC and LT are registered trademarks of Linear Technology Corporation.

The LT

1619 is a fixed frequency PWM controller for

implementing current mode DC/DC converters with mini-

mum external parts. The LT1619 operates with input

voltages ranging from 1.9V to 18V and is suitable for a

variety of battery-powered and distributed DC/DC con-

verters. The internal rail-to-rail N-channel MOSFET driver

operates either from the input in the nonbootstrapped

mode or from the output in bootstrapped operation. The

driver is designed to drive a low side power transistor in

boost, SEPIC, flyback and other topologies.

Converter efficiency is improved at heavy loads with a

53mV current sense voltage and at light load with Burst

Mode operation. The operating frequency is internally set

at 300kHz. The oscillator can also be synchronized exter-

nally up to 500kHz. No load quiescent current is 140µA and

shutdown current is 15µA.

The LT1619 is available in 8-lead MSOP and SO packages.

■

Wide V

Range: 1.9V to 18V

■

300kHz Fixed Frequency Current Mode Control

■

1A Rail-to-Rail N-Channel MOSFET Driver

■

Low 53mV Current Limit Threshold Voltage

Improves Efficiency

■

Implements Boost, SEPIC and Flyback Converters

Requiring Low Side Power Transistors

■

Internal Current Sense Amplifier

with Leading Edge Blanking

■

Up to 500kHz External Synchronization

■

Burst Mode

Operation for High Efficiency

at Light Load

■

140µA Quiescent Current

■

15µA Shutdown Current

■

8-Lead MSOP and SO Packages

■

3.3V to 5V DC/DC Converters

■

Distributed Power Supplies

■

Isolated Power Supplies

Figure 1. High Efficiency 3.3V to 5V DC/DC Converter

Burst Mode is a registered trademark of Linear Technology Corporation.

LOAD CURRENT (mA)

EFFICIENCY (%)

1 100 1000

1619 F01a

Efficiency

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

0.1µF

15nF

220pF

3.3V

5.6µH

Si9804

OUT

2.2A

SENSE

0.01Ω

1619 F01

75k

37.4k

12.4k

22µF

C1: PANASONIC EEFCDOK220R

OUT

: KEMET T495X227K010AS (×2)

D1: MBRD835L

L1: COILCRAFT DO5022P-562

OUT

440µF

S/S

GND

DRV

GATE

SENSE

LT1619

Summary of content (20 pages)

PAGE 1
LT1619 Low Voltage Current Mode PWM Controller U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT ®1619 is a fixed frequency PWM controller for implementing current mode DC/DC converters with minimum external parts. The LT1619 operates with input voltages ranging from 1.9V to 18V and is suitable for a variety of battery-powered and distributed DC/DC converters.
PAGE 2
LT1619 W W W AXI U U ABSOLUTE RATI GS (Note 1) Input Voltage (VIN) ................................... – 0.3V to 20V Gate Drive Supply Voltage (DRV) ............. – 0.3V to 20V Shutdown/Synch Voltage (S/S) ................ – 0.3V to 20V Feedback Voltage (FB) .............................................. VIN Compensation Voltage (VC) ...................................... 3V Gate Drive Output Current (GATE) ........................ ±1.5A Current Sense Voltage (SENSE) ................. – 0.
PAGE 3
LT1619 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = VDRV = 2.5V, VS/S = VIN, COMP open, VSENSE = 0V unless otherwise noted.
PAGE 4
LT1619 U W TYPICAL PERFOR A CE CHARACTERISTICS 45 200 IDLE MODE SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 40 35 TA = –40°C 30 TA = 25°C 25 TA = 85°C 20 15 10 2 4 VIN = 2.
PAGE 5
LT1619 U U U PI FU CTIO S S/S (Pin 1): Shutdown and Synchronization. Shutdown is active low with a typical threshold voltage of 0.9V. For normal operation, the S/S pin is tied to VIN. To externally synchronize the controller, drive the S/S pin with pulses. SENSE (Pin 5): The Input of the Current Sense Amplifier. The SENSE pin is connected to the source of the N-channel MOSFET and to a sense resistor to the ground.
PAGE 6
LT1619 U OPERATIO The LT1619 is a fixed frequency current mode switching regulator PWM controller that can be used in boost, SEPIC or flyback modes. The device operates from an input supply range of 1.9V to 18V, and has a separate supply pin (DRV) for the gate driver. The DRV pin can be bootstrapped to VOUT for additional gate enhancement in low voltage applications like 3.3V to 5V boost converters, or connected to the input supply for higher voltage inputs.
PAGE 7
LT1619 U OPERATIO or less than the number specified in Table 1 are acceptable. The maximum duty cycle is essentially unaffected by synchronization. The device will go into shutdown mode if the S/S pin voltage stays below the shutdown threshold of 0.45V for Table 1. Maximum Allowable Rise Time of Synchronization Pulse. Rise Time Can Be Slower if Clock Amplitude is Higher SYNCHRONIZATION AMPLITUDE (V) MAXIMUM ALLOWABLE RISE TIME (ns) 1.2 120 1.5 220 2.0 350 2.5 470 3.0 530 more than 33µs.
PAGE 8
LT1619 U W U U APPLICATIO S I FOR ATIO Power MOSFET MOSFET power dissipation can be separated into frequency independent and frequency dependent components. The RDS(ON) loss in the switch is the product of the mean square switch current and switch RDS(ON) and it does not vary with the operating frequency. The frequency-dependent switching losses consist of 1) switch transition loss due to finite rise and fall times of the drain source voltage and the drain current 2) gate switching loss, i.e.
PAGE 9
LT1619 U W U U APPLICATIO S I FOR ATIO Diode Schottky diodes are recommended for low output voltage applications because of their low forward voltage. Since Schottky diodes have negligible stored charge, charge dumping loss is also reduced. The reverse breakdown voltage of the diode should exceed the maximum reverse voltage stress of the topology used. The diode should also be able to carry the peak diode current with acceptable foward voltage.
PAGE 10
LT1619 U W U U APPLICATIO S I FOR ATIO fCORNER = 1 ≈ 5fS 2πROSCS VIN VZ (The input impedance of the sense amplifier at the SENSE pin is 2500Ω and ROS is typically less than 137Ω.) Typical values for ROS and CS are 100Ω and 1nF. The 100Ω value for ROS reduces Burst Mode threshold; use 10Ω and 10nF when this is not desireable.
PAGE 11
LT1619 U W U U APPLICATIO S I FOR ATIO Here the input voltage ripple is filtered with R3, R4 and C1 so as to prevent the input ripple from falsely tripping the LT1619 synchronization circuit. It is recommended that: and 1 R4 ≈ R3 5 1 ( Trickle Current Start from High Voltage Supplies ) 2π R3 || R4 C1 << fOSC Implementation of Hysteretic UVLO with External Synchronization The UVLO circuit shown in Figure 10 operates down to 0.9V supply voltage.
PAGE 12
LT1619 U W U U APPLICATIO S I FOR ATIO Increasing Ramp Compensation While Synchronizing The LT1619 is synchronized by forced discharge of the internal timing ramp. The timing ramp amplitude decreases as the synchronization frequency increases. Since the internal compensation ramp is derived from the timing ramp, reduced timing ramp results in diminished compensating ramp.
PAGE 13
LT1619 U W U U APPLICATIO S I FOR ATIO CDRV CIN2 R1 RC 1 8 2 7 S LT1619 R2 CZ CP 3 6 4 5 G M1 D G S M1 D RSENSE CIN1 GND COUT1, 2 VOUT D1 L1 VIN 1619 F14 Figure 14.
PAGE 14
LT1619 U W U U APPLICATIO S I FOR ATIO VIN 3.3V 1 2 3 CP 150pF RC 75k 4 S/S VIN FB DRV LT1619 VC GND GATE SENSE 8 CIN2 1µF CERAMIC 7 CDRV 0.1µF CERAMIC 6 L1 1µH + CIN1 300µF 5 CZ 15nF M1 D1 FDS6680A ×2 COUT1 RSENSE 220µF ×4 5V 8A + COUT2 10µF CERAMIC R1 37400Ω R2 12400Ω 1619 F15a CIN1: SANYO POSCAP 6TPB150M ×2 COUT1: SANYO POSCAP 10TPB220M ×4 D1: MOTOROLA MBRB1545CT L1: SUMIDA CEPH149-1R0 RSENSE: PANASONIC 0.002Ω 1W Figure 15a. 3.3V to 5V/8A Boost Converter 89 VIN = 3.
PAGE 15
LT1619 U W U U APPLICATIO S I FOR ATIO VIN 5V 1 2 3 CP 47pF RC 68.1k 4 S/S VIN FB DRV LT1619 VC GND GATE SENSE 8 CIN2 1µF CERAMIC 7 CDRV 0.1µF CERAMIC 6 L1 1.8µH + CIN1 100µF 5 CZ 2200pF M1 D1 FDS6690A ×2 COUT1 RSENSE 600µF 12V 5A + COUT2 10µF CERAMIC R1 107k R2 12400Ω 1619 F15a CIN1: SANYO OS-CON 10SA100M COUT1: SANYO OS-CON 16SA150M ×4 D1: MOTOROLA MBRB1545CT L1: SUMIDA CDEP149-1R8 RSENSE: PANASONIC 0.002Ω 1W Figure 16a.
PAGE 16
LT1619 U TYPICAL APPLICATIO S VIN 4.75V TO 5.25V T1 –48V/0.5A • • 470µF 35V SANYO MV-GX + • + MBRS340T3 470µF 35V SANYO MV-GX 1µF + 1500µF 6.3V SANYO MV-GX • 1N749 4.3V • 4.7µF FILM 15Ω • 1 1.1k 2 3 2.2nF 36k 4 S/S VIN FB DRV LT1619 VC GATE GND SENSE 8 4.7µF FILM MBRS340T3 7 6 10µF SUD45N05-20L 50V, 0.018Ω 43nC 1M 30Ω 5 12k 220pF 2N5210 10.5k 1% 0.007Ω 22nF 2N5210 432k 1% 1619 F17a T1: COILTRONICS CTX02-14261, EFD20-3F3, 6 WINDINGS EACH, 12µH Figure 17a.
PAGE 17
LT1619 U TYPICAL APPLICATIO S 10k CNY17-3 6.2V VIN 10.5V TO 13.7V 330pF 100V 43Ω 1/4W T1 • 0.22µF 50V 8.1V 1k 1W 43Ω W1 2.2µF 40V 470pF • • MBRS1100T3 330pF W4 50V 1 –32.5V 82k 2 10k 150µF 20V SANYO 20SV150M (OS-CON) 3 100Ω 4 FB DRV LT1619 VC GND GATE SENSE 1µF 50V 2.2µF 40V • 470Ω 2.49k 121Ω LT1431 1 8 COLL REF 2 7 NC NC 3 6 V+ FGND 4 5 NC SGND –65V MBRS1100T3 8 7 6 10µF T1 PHILIPS EFD20-3F3-A100-S CORE SET (0.013" GAP, AI = 100nH/T2 IRLR024N 55V, 0.
PAGE 18
LT1619 U PACKAGE DESCRIPTION MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.2 – 3.45 (.126 – .136) 0.42 ± 0.04 (.0165 ± .0015) TYP 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 8 7 6 5 0.52 (.206) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.90 ± 0.15 (1.93 ± .006) DETAIL “A” 0° – 6° TYP GAUGE PLANE 0.53 ± 0.015 (.021 ± .006) DETAIL “A” 1 2 3 4 1.10 (.043) MAX 0.86 (.
PAGE 19
LT1619 U PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 7 6 5 N N .245 MIN .160 ±.005 1 .030 ±.005 TYP .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 2 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.
PAGE 20
LT1619 U TYPICAL APPLICATIO VIN 4V TO 28V T1 7 C4 1.5µF 100V R3 5.6k 9 10 • • 12 2 1 5• •4 8 3 6• • 11 C5 1.5µF 100V VOUT 5V 0.5A D3 MBRS0530T1 Q1 FMMT3904 D4 1N4687 4.3V LOW LEVEL (IZT = 50µA) D2 MBRS340T3 8 7 Q3 MMFT3055VL 6 VIN DRV GATE 5 R7 30Ω SENSE LT1619 2 FB S/S GND 1 4 C8 1µF 16V R5 100Ω R6 3.74k 1% C1 0.022µF C6 10µF 10V VC 3 R9 2.2k C9 2.2nF C7 220pF R8 0.015Ω R10 1.