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General Description

The MAX1800 provides a complete power-supply solu-

tion for digital still cameras and video cameras. The

device integrates a high-efficiency main step-up DC-DC

converter, three auxiliary step-up controllers, and an

uncommitted gain block that drives an external P-channel

MOSFET for a linear regulator. The MAX1800 is targeted

for applications that use either two or three primary cells

or a single lithium-ion (Li+) battery.

The main DC-DC converter accepts inputs from +0.7V to

+5.5V and regulates a resistor-adjustable output from

2.7V to 5.5V. It uses an internal synchronous rectifier to

regulate the output with 95% efficiency. An adjustable

operating frequency facilitates designs for optimum size,

cost, and efficiency.

The auxiliary step-up controllers can be used to power a

digital camera’s CCD, LCD, and backlight. The MAX1800

also features expandability by supplying power, oscillator

signal, and reference to the MAX1801, a low-cost slave

DC-DC controller that supports step-up, SEPIC, and fly-

back configurations.

The MAX1800 is available in a space-saving 32-pin TQFP

package (5mm x 5mm body), and the MAX1801 is avail-

able in an 8-pin SOT package. An evaluation kit

(MAX1800EVKIT) featuring both devices is available to

expedite designs.

________________________Applications

Digital Still Cameras PDAs

Digital Video Cameras DVD Players

Hand-Held Devices

Internet Access Tablets

Features

♦ +0.7V to +5.5V Input Voltage Range

♦ Main DC-DC Converter

95% Efficiency

+2.7V to +5.5V Adjustable Output Voltage

1.5A Load Current

♦ Uncommitted Gain Block for Linear Regulator

♦ Three Independent Auxiliary Step-Up Controllers

Adjustable Maximum Duty Cycle

♦ Oscillator and Reference Outputs to Drive External

Slave Controllers (MAX1801)

♦ Power-Ready Output

♦ Up to 1MHz Switching Frequency

♦ 1µA Supply Current in Shutdown Mode

♦ Internal Soft-Start Control

♦ Overload Protection for all DC-DC Converters

♦ Compact 32-Pin TQFP Package (5mm x 5mm body)

MAX1800

Digital Camera Step-Up

Power Supply

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-1833; Rev 0; 10/00

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

Ordering Information

MAX1800

MASTER

MAX1801

SLAVE

INPUT

0.7V TO 5.5V

OSC REF

MOTOR

TFT

CCD

CCFL

CORE

MAIN

MAX1800

TQFP

TOP VIEW

32 28

293031

ON3

FB3

COMP3

DCON3

DL3

ONA

1611 12

ON2

COMP2

FB2

OUT

DCON2

GND

REF

OSC

RDYM

24 ONM

POUT

PGND

COMPM

FBM

8DL2

POUT

DCON1

COMP1

FB1

ON1

DL1

1PGND

Pin Configuration

PART TEMP. RANGE

PIN-PACKAGE

MAX1800EHJ -40°C to +85°C 32 TQFP

Summary of content (24 pages)

PAGE 1
9-1833; Rev 0; 10/00 KIT ATION EVALU E L B AVAILA Digital Camera Step-Up Power Supply Features ♦ +0.7V to +5.5V Input Voltage Range ♦ Main DC-DC Converter 95% Efficiency +2.7V to +5.5V Adjustable Output Voltage 1.
PAGE 2
MAX1800 Digital Camera Step-Up Power Supply ABSOLUTE MAXIMUM RATINGS OUT, POUT, ON_, DCON_, FB_, RDYM to GND .....-0.3V to +6.0V PGND to GND ......................................................-0.3V to +0.3V OUT to POUT_ ......................................................-0.3V to +0.3V LX, DL_, AO to PGND .............................-0.3V to (POUT + 0.3V) REF, OSC, AI, COMP_ to GND..................-0.3V to (OUT + 0.
PAGE 3
Digital Camera Step-Up Power Supply (Circuit of Figure 1, VOUT = VPOUT = 3.3V, PGND = GND, VONM = 3.3V, VON1 = VON2 = VON3 = VONA = 0, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS LOGIC INPUTS (ONM, ON1, ON2, ON3, ONA) Input Low Level VIL Input High Level VIH 1.1V < VOUT < 1.8V (ONM only) 0.2 1.8V < VOUT < 5.5V 0.4 1.1V < VOUT < 1.8V (ONM only) 1.8V < VOUT < 5.5V Input Leakage Current VOUT 0.
PAGE 4
MAX1800 Digital Camera Step-Up Power Supply ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VOUT = VPOUT = 3.3V, PGND = GND, VONM = 3.3V, VON1 = VON2 = VON3 = VONA = 0, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 1.23 1.25 1.27 V ANALOG GAIN BLOCK AI Feedback Regulation Voltage VAO = VOUT - 1.25V AI Input Common-Mode Range -0.1 AI Input Current VAI = 1.
PAGE 5
Digital Camera Step-Up Power Supply MAIN OUTPUT EFFICIENCY vs. LOAD CURRENT MAIN OUTPUT EFFICIENCY vs. LOAD CURRENT VIN = 2.0V 70 VIN = 1.5V 60 50 40 80 VIN = 1.5V 40 30 20 10 VOUT = 2.7V VOUT = 3.3V 0 1 10 100 10 100 1000 LOAD CURRENT (mA) MAIN OUTPUT EFFICIENCY vs. LOAD CURRENT MINIMUM STARTUP CURRENT vs. INPUT VOLTAGE VIN = 2.5V 70 VIN = 2.0V 60 VIN = 1.5V 50 500 STARTUP CURRENT (mA) 80 40 30 MAX1800 toc04 600 MAX1800 toc03 VIN = 3.
PAGE 6
Typical Operating Characteristics (continued) (Circuit of Figure 1, VINPUT = 2.4V, TA = +25°C, unless otherwise noted.) AUXILIARY CONTROLLER MAXIMUM DUTY CYCLE vs. VDCON_ FB_ TO COMP_ SMALL-SIGNAL OPEN-LOOP FREQUENCY RESPONSE 60 40 20 MAX1800 toc08 50 40 30 20 10 0 0 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1 VDCON_ (V) 100 1000 OSCILLATOR FREQUENCY vs.
PAGE 7
Digital Camera Step-Up Power Supply AUXILIARY CONTROLLER STARTUP RESPONSE STARTUP SEQUENCE MAX1800 toc14 MAX1800 toc13 3.3V VON_ 5V/div 0V VONM 5V/div 0V MAIN OUTPUT VOLTAGE 2V/div VOUT 2V/div 0V 0V IIN 0.5A/div LDO OUTPUT VOLTAGE 2V/div 0V AUXILIARY OUTPUT VOLTAGE 2V/div 0A 0V 1.
PAGE 8
Digital Camera Step-Up Power Supply MAX1800 Pin Description PIN NAME 1, 19 PGND 2 DL1 External MOSFET Gate Drive Output for Auxiliary Controller 1. DL1 swings between POUT and GND with typical 500mA drive current. Connect DL1 to the gate of the external switching N-channel MOSFET for auxiliary controller 1. 3 ON1 Enable Input for Auxiliary Controller 1. Connect ON1 to POUT to automatically start auxiliary controller 1. 4 FB1 Feedback Input for Auxiliary Controller 1.
PAGE 9
Digital Camera Step-Up Power Supply PIN NAME FUNCTION 24 ONM Main Converter Enable Input. High level turns the main converter on. Connect ONM to POUT to automatically start the main converter. When the main converter is off, all other outputs are disabled. 25 AI Analog Gain Block Input. AI is the positive input to the gain block. The negative input is internally connected to the 1.25V reference. 26 AO Analog Gain Block Output. AO is a push-pull output driven between GND and POUT.
PAGE 10
MAX1800 Digital Camera Step-Up Power Supply INPUT 0.7V TO 5.5V +15V POUT 4 DCON +5V 8 6 5 DL POUT 7 IN OSC MAXIM MAX 1801 CCD BIAS LX ROSC 1 16 OSC DL1 MAX1800 REF -7.5V 2 COSC FB COMP 20, 21 14 3 0.1µF GND 2 6 12 28 FB1 4 REF +18V LCD BIAS DCON1 +12V DCON2 DCON3 +7V 32 30 DL2 DL3 FB3 FB2 RCM RC1 RC2 RC3 18 COMPM 5 COMP1 11 COMP2 COMP3 29 AO 8 10 26 LDO 1.8V AI 25 INPUT CCM CC1 ON CC3 7, 22 24 OFF 27 3 POUT MAIN 3.
PAGE 11
Digital Camera Step-Up Power Supply MAX1800 UNDERVOLTAGE LOCKOUT OUT MAX1800 IC POWER 2.35V EN EN STARTUP OSCILLATOR POUT POUT MAIN PWM CONTROLLER Q Q1 D P LX ONM REF GND OSC 1.25V EN RDY ON REFERENCE REF EN OSCILLATOR FBM LX OSC FB Q2 N PGND PGND COMP COMPM FB1 COMP1 DCON1 AUX1 EN OSC Q FB COMP DUTY DL1 FB2 COMP2 DCON2 AUX2 EN OSC Q FB COMP DUTY DL2 FB3 COMP3 DCON3 AUX3 EN OSC Q FB COMP DUTY DL3 AI GAIN BLOCK ON1 ON2 VREF AO EN RDYM N ON3 ONA 0.9VREF Figure 2.
PAGE 12
MAX1800 Digital Camera Step-Up Power Supply FB COMP R Q DL_ LEVEL SHIFT REFI SOFTSTART* REF S DCON CLK OSC *SOFT-START RAMPS REFI FROM 0V TO VREF IN 1024 CLK CYCLES. FAULT PROTECTION ENABLE Figure 3. PWM Auxiliary Controller Block Diagram Analog Gain Block The MAX1800 analog gain block is a voltage amplifier with a gain of 100 and a push-pull output stage with 2.5mA drive capability.
PAGE 13
Digital Camera Step-Up Power Supply Ready-Main (RDYM) Output ROSC The MAX1800 power-ready RDYM comparator opendrain output sinks up to 1mA if the main output drops 10% below its regulation voltage. When FBM exceeds the RDYM trip level, the RDYM output becomes high impedance to indicate that the main output is within the limits of regulation. The RDYM comparator has 1% hysteresis to prevent oscillations near the trip threshold. Connect RDYM to POUT with a 1MΩ pullup resistor. OSC COSC VREF (1.
PAGE 14
MAX1800 Digital Camera Step-Up Power Supply Setting the Output Voltages Set the MAX1800 output voltages by connecting a resistive voltage-divider from the output voltage to the corresponding FB_ input. The FB_ input bias current is less than 100nA, so choose RL1 (the low-side FB_-toGND resistor) to be 100kΩ. Choose RH1 (the high-side output-to-FB_ resistor) according to the relation: V  RH1 = RL1  OUT − 1  1.
PAGE 15
Digital Camera Step-Up Power Supply VRIPPLE ≈ IL(PEAK) ✕ ESR where IL(PEAK) is the peak inductor current. Ceramic capacitors typically have lower ESR than tantalum capacitors, but with relatively small capacitance that dominates the impedance at the switching frequency. In turn, the output ripple is approximately: VRIPPLE ≈ IL(PEAK) ✕ ZC where IL(PEAK) is the peak inductor current, and ZC ≈ 1 / (2 π fOSC COUT ).
PAGE 16
MAX1800 Digital Camera Step-Up Power Supply To determine the compensation components: 1) Find the frequency of the right-half-plane zero: V (1 − DM )2 fRHPZ = POUT 2π ILOAD(MAX) L where VPOUT is the output voltage, ILOAD(MAX) is the maximum load current, L is the inductor value, and D M is the duty-cycle under maximum load, specifically: DM = [ ] VPOUT − VIN + ILIM (RPCH + ESRL ) VPOUT + ILIM (RPCH + RNCH ) where I LIM is the average inductor current under maximum load, ESRL is the equivalent series re
PAGE 17
Digital Camera Step-Up Power Supply Discontinuous Inductor Current For discontinuous inductor current, the PWM converter has a single pole.
PAGE 18
MAX1800 Digital Camera Step-Up Power Supply 4) Place the compensation zero at the same frequency as the maximum output pole frequency (in Hz): ZC = 1 2π RCCC = 2(VOUT - VIN) 2π(VOUT - VIN ) RLOAD(MIN) COUT Solving for CC:   VOUT - VIN CC = COUT VOUT    RC IOUT(MAX) 2(VOUT - VIN )  Use values of CC less than 10nF. If the above calculation determines that the capacitor should be greater than 10nF, use CC = 10nF, skip step 4 , and proceed to step 5.
PAGE 19
Digital Camera Step-Up Power Supply MAIN GAIN AVDC MAX1800 180° PC INPUT 1-CELL LITHIUM-ION L1 L2 PHASE ZC=PO 90° GAIN (dB) IN DCON PHASE O dB C2 DL Q1 PART OF MAX1800 PHASE MARGIN ZO GAIN MARGIN OUTPUT 3.3V D1 R1 FB 0° COMP ZrRHP R2 FREQUENCY RC Figure 7. MAX1800 Continuous-Current, Voltage-Mode, Step-Up Converter Bode Plot The Bode plot of the loop gain of this control circuit is shown in Figure 7.
PAGE 20
MAX1800 Digital Camera Step-Up Power Supply Applications Information Using the MAX1801 with the MAX1800 Step-Up Master The MAX1801 is a slave DC-DC controller that can be used with the MAX1800 to generate additional output voltages. It does not generate its own reference or oscillator. Instead, it uses the reference and oscillator of the MAX1800 step-up master converter controller (Figure 1). The MAX1801 controller operation and design are similar to that for the MAX1800 auxiliary controllers.
PAGE 21
Digital Camera Step-Up Power Supply MAX1800 D3 INPUT VOLTAGE (FROM MAIN OUTPUT) VOUTC3 INPUT 1-CELL LITHIUM-ION D1 MAIN PART OF MAX 1800 C1 L Q1 D2 IN AI VOUT+ DCON DL COUT C2 Q1 PART OF MAX1800 R1 R1 LOAD RESISTOR (RL) AI FB VREF COMP R2 R2 ONA ON OFF RC CC Figure 11. Linear Regulator Figure 10. Auxiliary Charge-Pump Configuration V  R1 = R2  OUT − 1 V  REF  Choose the MOSFET for low dropout.
PAGE 22
MAX1800 Digital Camera Step-Up Power Supply up/step-down DC/DC converter. One way of making such a circuit is to add a low-dropout linear regulator after a step-up converter. When the battery voltage is below the output voltage, the step-up converter generates the higher voltage, and the LDO regulator is in dropout. When the battery voltage is greater than the output voltage, the LDO drops the voltage to the required output voltage.
PAGE 23
Digital Camera Step-Up Power Supply 32L TQFP, 5x5x01.0.
PAGE 24
Digital Camera Step-Up Power Supply MAX1800 Package Information (continued) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.