Datasheet

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Constant Frequency Current-Mode

Step-Down DC-to-DC Controller in TSOT

Data Sheet

ADP1864

Rev. C

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FEATURES

Wide input voltage range: 3.15 V to 14 V

Wide output voltage range: 0.8 V to input voltage

Pin-to-pin compatible with LTC1772, LTC3801

Up to 94% efficiency

0.8 V ± 1.25% reference accuracy over temperature

Internal soft start

100% duty cycle for low dropout voltage

Current-mode operation for good line and load

transient response

7 μA shutdown supply current

235 μA quiescent supply current

Short-circuit and overvoltage protection

Small 6-lead TSOT package

Supported by ADIsimPower™ design tool

APPLICATIONS

Wireless devices

1- to 3-cell Li-Ion battery-powered applications

Set-top boxes

Processor core power supplies

Hard disk drives

GENERAL DESCRIPTION

The ADP1864 is a compact, inexpensive, constant-frequency,

current-mode, step-down dc-to-dc controller. The ADP1864

drives a P-channel MOSFET that regulates an output voltage as

low as 0.8 V with ±1.25% accuracy, for up to 5 A load currents,

from input voltages as high as 14 V.

The ADP1864 provides system flexibility by allowing accurate

setting of the current limit with an external resistor, and the

output voltage is easily adjustable using two external resistors.

The ADP1864 includes an internal soft start to allow quick

power-up while preventing input inrush current. Additional

safety features include short-circuit protection, output overvoltage

protection, and input undervoltage protection. Current-mode

control provides fast and stable load transient performance,

while the 580 kHz operating frequency allows a small inductor

to be used in the system. To further the life of a battery source,

the controller turns on the external P-channel MOSFET 100%

of the duty cycle during dropout.

The ADP1864 operates over the −40°C to +125°C temperature

range and is available in a small, low profile, 6-lead TSOT package.

TYPICAL APPLICATIONS DIAGRAM

05562-001

ADP1864

COMP

GND

PGATE

174kΩ

80.6kΩ

25kΩ

470pF

68pF

47µF

0.03Ω

10µF

2.5V, 2.0A

= 3.15V TO 14V

5µH

Figure 1.

Summary of content (16 pages)

PAGE 1
Constant Frequency Current-Mode Step-Down DC-to-DC Controller in TSOT ADP1864 Data Sheet FEATURES GENERAL DESCRIPTION Wide input voltage range: 3.15 V to 14 V Wide output voltage range: 0.8 V to input voltage Pin-to-pin compatible with LTC1772, LTC3801 Up to 94% efficiency 0.8 V ± 1.
PAGE 2
ADP1864 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Soft Start .........................................................................................9 Applications ....................................................................................... 1 Applications Information .............................................................. 10 General Description ...............................................
PAGE 3
Data Sheet ADP1864 SPECIFICATIONS VIN = 5 V, TJ = 25°C, unless otherwise noted. Table 1.
PAGE 4
ADP1864 Data Sheet ABSOLUTE MAXIMUM RATINGS Table 2. Parameter IN to GND CS, PGATE to GND FB, COMP to GND θJA 2-Layer (SEMI Standard Board) θJA 4-Layer (JEDEC Standard Board) Operating Junction Temperature Range Storage Temperature Range Lead Temperature Rework Temperature (J-STD-020B) Peak Reflow Temperature, (20 sec to 40 sec, J-STD-020B) Rating −0.3 V to +16 V −0.3 V to (VIN + 0.3 V) −0.
PAGE 5
Data Sheet ADP1864 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS COMP 1 6 PGATE ADP1864 5 TOP VIEW (Not to Scale) FB 3 4 IN CS 05562-003 GND 2 Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1 Mnemonic COMP 2 GND 3 FB 4 CS 5 IN 6 PGATE Description Regulator Compensation Node. COMP is the output of the internal transconductance error amplifier. Connect a series RC from COMP to GND to compensate for the control loop.
PAGE 6
ADP1864 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS 0.810 0.8 VIN = 5V 0.805 COMP RISING 0.6 COMP (V) 0.5 0.800 0.4 COMP FALLING 0.3 0.795 0.1 –20 0 20 40 60 80 100 0 –40 120 05562-007 0.790 –40 0.2 05562-004 REFERENCE VOLTAGE (V) 0.7 –20 0 20 TEMPERATURE (°C) 40 60 80 100 120 TEMPERATURE (°C) Figure 3. Reference Voltage vs. Temperature Figure 6. COMP Shutdown Threshold vs. Temperature 2.52 600 VIN = 5V 2.50 2.48 580 VOUT (V) 570 2.46 2.
PAGE 7
Data Sheet ADP1864 650 12 TEMPERATURE = 25°C 630 11 620 610 FREQUENCY (kHz) 10 VIN = 16V 9 8 VIN = 5V 7 590 580 570 560 550 530 VIN = 3.15V 5 –40 –20 0 20 40 60 80 100 520 510 500 3 120 VIN = 16V VIN = 12V VIN = 7V 270 250 VIN = 5V VIN = 4V 230 VIN = 3.1V 05562-011 210 190 –40 –20 0 20 40 60 7 9 11 Figure 11. Oscillator Frequency vs. Input Voltage Figure 9. Shutdown Supply Current vs.
PAGE 8
ADP1864 Data Sheet THEORY OF OPERATION positive input to the error amplifier is driven by a 0.8 V band gap reference. An increase in the load current causes a small drop in the feedback voltage, in turn causing an increase in the COMP voltage and, therefore, the duty cycle. The resulting increase in the on time of the FET provides the additional current required by the load. The ADP1864 is a constant frequency (580 kHz), current-mode buck controller. PGATE drives the gate of the external P-channel FET.
PAGE 9
Data Sheet ADP1864 SHORT-CIRCUIT PROTECTION OVERVOLTAGE LOCKOUT PROTECTION (OVP) If there is a short across the output load, the voltage at the feedback pin (FB) drops rapidly. When the FB voltage drops below 0.35 V, the ADP1864 reduces the oscillator frequency to 190 kHz. The increase in the oscillator period allows the inductor additional time to discharge, preventing the output current from running away. Once the output short is removed and the feedback voltage increases above the 0.
PAGE 10
ADP1864 Data Sheet APPLICATIONS INFORMATION ADIsimPower DESIGN TOOL RSENSE ( MIN ) = 0.95 To determine the worst-case inductor ripple current, output voltage ripple, and slope compensation factor, establish the system maximum and minimum duty cycle. The duty cycle is calculated by the equation Duty Cycle (DC ) = 0.85 0.75 0.65 0.55 05562-014 0.45 0.35 0 0.1 0.2 0.3 (1) VIN + VD (4) 1.
PAGE 11
Data Sheet ADP1864 MOSFET INPUT CAPACITOR Choose the external P-channel MOSFET based on the following: threshold voltage (VT), maximum voltage and current ratings, RDS(ON), and gate charge. The minimum operating voltage of the ADP1864 is 3.15 V. Choose a MOSFET with a VT that is at least 1 V lower than the minimum input supply voltage used in the application. The input capacitor provides a low impedance path for the pulsed current drawn by the external P-channel FET.
PAGE 12
ADP1864 Data Sheet LAYOUT CONSIDERATIONS R2 1 All noisy nodes (P-channel drain, power diode cathode, and inductor terminal) are located along the bottom portion of the evaluation board on the top layer (see Figure 16). A substantial amount of copper has been allocated for this area with ample track spacing to minimize coupling (crosstalk) effects during switching.
PAGE 13
Data Sheet ADP1864 EXAMPLE APPLICATIONS CIRCUITS 25kΩ 1 470pF COMP PGATE 6 ADP1864 68pF 2 GND VIN = 4.5V TO 5.5V 0.03Ω 10µF IN 5 3.3µH 80.6kΩ 3 FB CS 4 3.3V, 2.0A 47µF 255kΩ 05562-018 RSENSE LRC-LR1206-01-R030-F MOSFET FAIRCHILD SEMI FDC638P INDUCTOR TOKO FDV0630-3R3M DIODE SYNSEMI SK22 CIN LMK325BJ106KN COUT SANYO POSCAP 6TPB47M Figure 18. Application Circuit for VOUT = 3.3 V, 2 A Load 1 470pF COMP 68pF 80.6kΩ PGATE 6 2 GND 3 FB VIN = 3.15V TO 14V 0.
PAGE 14
ADP1864 Data Sheet OUTLINE DIMENSIONS 2.90 BSC 6 5 4 2.80 BSC 1.60 BSC 1 2 PIN 1 INDICATOR 3 0.95 BSC 1.90 BSC *1.00 MAX SEATING PLANE 0.10 MAX 0.50 0.30 0.20 0.08 8° 4° 0° 0.60 0.45 0.30 *COMPLIANT TO JEDEC STANDARDS MO-193-AA WITH THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS. 102808-A *0.90 0.87 0.84 Figure 20.
PAGE 15
Data Sheet ADP1864 NOTES Rev.