Datasheet LTC3700 (Analog Devices)
| Hersteller | Analog Devices |
| Beschreibung | Constant Frequency Step-Down DC/DC Controller with LDO Regulator |
| Seiten / Seite | 16 / 1 — FEATURES. DESCRIPTIO. Dual Output Regulator in Tiny 10-Pin MSOP. High … |
| Dateiformat / Größe | PDF / 221 Kb |
| Dokumentensprache | Englisch |
FEATURES. DESCRIPTIO. Dual Output Regulator in Tiny 10-Pin MSOP. High Efficiency: Up to 94%. Wide V. IN Range: 2.65V to 9.8V
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LTC3700 Constant Frequency Step-Down DC/DC Controller with LDO Regulator
U FEATURES DESCRIPTIO
■
Dual Output Regulator in Tiny 10-Pin MSOP
The LTC®3700 is a constant frequency current mode step- ■
High Efficiency: Up to 94%
down (buck) DC/DC controller with excellent AC and DC ■
Wide V
load and line regulation. The on-chip 150mA low dropout
IN Range: 2.65V to 9.8V
■
Constant Frequency 550kHz Operation
(LDO) linear regulator can be powered from the buck ■
150mA LDO Regulator with Current Limit and
controller’s input supply, its own independent input supply
Thermal Shutdown Protection
or the buck regulator’s output. The buck controller incor- ■ High Output Currents Easily Achieved porates an undervoltage lockout feature that shuts down the ■ Burst Mode® Operation at Light Load controller when the input voltage falls below 2.1V. ■ Low Dropout: 100% Duty Cycle The buck regulator provides a ±2.5% output voltage accu- ■ Current Mode Operation for Excellent Line and Load racy. It consumes only 210µA of quiescent current in nor- Transient Response mal operation with the LDO consuming an additional 50µA. ■ 0.8V Reference Allows Low Output Voltages In shutdown, a mere 10µA (combined) is consumed. ■ Low Quiescent Current: 260µA Total ■ Shutdown Mode Draws Only 10 For applications where efficiency is a prime consideration, µA Supply Current ■ Common Power Good Output for Both Supplies the buck controller is configured for Burst Mode operation which enhances efficiency at low output current. To fur-
U
ther maximize the life of a battery source, the external
APPLICATIO S
P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High constant operating frequency of ■ Notebook Computers 550kHz allows the use of a small external inductor. ■ Portable Instruments ■ One or Two Li-Ion Battery-Powered Applications The LDO is protected by both current limit and thermal , LTC and LT are registered trademarks of Linear Technology Corporation. shutdown circuits. Burst Mode is a registered trademark of Linear Technology Corporation. The LTC3700 is available in a tiny 10-pin MSOP.
U TYPICAL APPLICATIO
V V IN1 IN2 5V 3.3V
Buck Efficiency vs Load Current
C1 C3 R1 10µF 0.068Ω V 10µF IN VIN2 90 10V 10V VOUT = 1.8V V SENSE– LDO OUT2 86 RSENSE = 0.068Ω VIN = 3.3V 2.5V AT 169k 150mA 82 L1 M1 PGATE C4 V 10µH V OUT1 FB2 2.2µF 78 1.8V 16V 78.7k 74 VIN = 5V AT 1A 100k D1 LTC3700 70 V C2 + IN = 4.2V 47µF 66 6V 80.6k EFFICIENCY (%) C1, C3: TAIYO YUDEN EMK325BJ106MNT 62 VFB PGOOD C2: SANYO POSCAP 6TPA47M C4: MURATA GRM42-6X7R225K016AL 58 10k ITH/RUN GND D1: MOTOROLA MBRM120T3 54 L1: COILTRONICS UP1B-100 220pF M1: Si3443DV 50 R1: DALE 0.25W 3700 F01 1 10 100 1000 LOAD CURRENT (mA) 3700 F01a
Figure 1. High Efficiency 5V to 1.8V/1A Buck with 3.3V to 2.5V/150mA LDO
3700f 1
U FEATURES DESCRIPTIO
■
Dual Output Regulator in Tiny 10-Pin MSOP
The LTC®3700 is a constant frequency current mode step- ■
High Efficiency: Up to 94%
down (buck) DC/DC controller with excellent AC and DC ■
Wide V
load and line regulation. The on-chip 150mA low dropout
IN Range: 2.65V to 9.8V
■
Constant Frequency 550kHz Operation
(LDO) linear regulator can be powered from the buck ■
150mA LDO Regulator with Current Limit and
controller’s input supply, its own independent input supply
Thermal Shutdown Protection
or the buck regulator’s output. The buck controller incor- ■ High Output Currents Easily Achieved porates an undervoltage lockout feature that shuts down the ■ Burst Mode® Operation at Light Load controller when the input voltage falls below 2.1V. ■ Low Dropout: 100% Duty Cycle The buck regulator provides a ±2.5% output voltage accu- ■ Current Mode Operation for Excellent Line and Load racy. It consumes only 210µA of quiescent current in nor- Transient Response mal operation with the LDO consuming an additional 50µA. ■ 0.8V Reference Allows Low Output Voltages In shutdown, a mere 10µA (combined) is consumed. ■ Low Quiescent Current: 260µA Total ■ Shutdown Mode Draws Only 10 For applications where efficiency is a prime consideration, µA Supply Current ■ Common Power Good Output for Both Supplies the buck controller is configured for Burst Mode operation which enhances efficiency at low output current. To fur-
U
ther maximize the life of a battery source, the external
APPLICATIO S
P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High constant operating frequency of ■ Notebook Computers 550kHz allows the use of a small external inductor. ■ Portable Instruments ■ One or Two Li-Ion Battery-Powered Applications The LDO is protected by both current limit and thermal , LTC and LT are registered trademarks of Linear Technology Corporation. shutdown circuits. Burst Mode is a registered trademark of Linear Technology Corporation. The LTC3700 is available in a tiny 10-pin MSOP.
U TYPICAL APPLICATIO
V V IN1 IN2 5V 3.3V
Buck Efficiency vs Load Current
C1 C3 R1 10µF 0.068Ω V 10µF IN VIN2 90 10V 10V VOUT = 1.8V V SENSE– LDO OUT2 86 RSENSE = 0.068Ω VIN = 3.3V 2.5V AT 169k 150mA 82 L1 M1 PGATE C4 V 10µH V OUT1 FB2 2.2µF 78 1.8V 16V 78.7k 74 VIN = 5V AT 1A 100k D1 LTC3700 70 V C2 + IN = 4.2V 47µF 66 6V 80.6k EFFICIENCY (%) C1, C3: TAIYO YUDEN EMK325BJ106MNT 62 VFB PGOOD C2: SANYO POSCAP 6TPA47M C4: MURATA GRM42-6X7R225K016AL 58 10k ITH/RUN GND D1: MOTOROLA MBRM120T3 54 L1: COILTRONICS UP1B-100 220pF M1: Si3443DV 50 R1: DALE 0.25W 3700 F01 1 10 100 1000 LOAD CURRENT (mA) 3700 F01a
Figure 1. High Efficiency 5V to 1.8V/1A Buck with 3.3V to 2.5V/150mA LDO
3700f 1