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PDF MAX1800 Data sheet ( Hoja de datos )
| Número de pieza | MAX1800 | |
| Descripción | Digital Camera Step-Up Power Supply | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1833; Rev 0; 10/00
EVAALVUAAILTAIOBNLEKIT
Digital Camera Step-Up
Power Supply
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
Digital Video Cameras
PDAs
DVD Players
Hand-Held Devices
Internet Access Tablets
Features
o +0.7V to +5.5V Input Voltage Range
o Main DC-DC Converter
95% Efficiency
+2.7V to +5.5V Adjustable Output Voltage
1.5A Load Current
o Uncommitted Gain Block for Linear Regulator
o Three Independent Auxiliary Step-Up Controllers
Adjustable Maximum Duty Cycle
o Oscillator and Reference Outputs to Drive External
Slave Controllers (MAX1801)
o Power-Ready Output
o Up to 1MHz Switching Frequency
o 1µA Supply Current in Shutdown Mode
o Internal Soft-Start Control
o Overload Protection for all DC-DC Converters
o Compact 32-Pin TQFP Package (5mm x 5mm body)
PART
MAX1800EHJ
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
32 TQFP
TOP VIEW
Pin Configuration
32 31 30 29 28 27 26 25
Typical Operating Circuit
INPUT
0.7V TO 5.5V
MAX1800
MASTER
CCD
TFT
CCFL
CORE
MAIN
OSC REF
MAX1801
SLAVE
MOTOR
PGND 1
DL1 2
ON1 3
FB1 4
COMP1 5
DCON1 6
POUT 7
DL2 8
MAX1800
24 ONM
23 RDYM
22 POUT
21 LX
20 LX
19 PGND
18 COMPM
17 FBM
9 10 11 12 13 14 15 16
TQFP
________________________________________________________________ Maxim Integrated Products 1
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.
1 page  
Digital Camera Step-Up
Power Supply
Typical Operating Characteristics
(Circuit of Figure 1, VINPUT = 2.4V, TA = +25°C, unless otherwise noted.)
MAIN OUTPUT
EFFICIENCY vs. LOAD CURRENT
100
VIN = 2.5V
90
80
70 VIN = 2.0V
60 VIN = 1.5V
50
40
MAIN OUTPUT
EFFICIENCY vs. LOAD CURRENT
100
90 VIN = 3.0V
80
70 VIN = 2.5V
60 VIN = 2.0V
50 VIN = 1.5V
40
30 30
20 20
10 VOUT = 2.7V
0
1 10 100 1000
LOAD CURRENT (mA)
10
0
1
VOUT = 3.3V
10 100
LOAD CURRENT (mA)
1000
MAIN OUTPUT
EFFICIENCY vs. LOAD CURRENT
100
90 VIN = 3.0V
80
70 VIN = 2.5V
60 VIN = 2.0V
50 VIN = 1.5V
40
30
20
10 VOUT = 5V
0
1 10 100 1000
LOAD CURRENT (mA)
MINIMUM STARTUP CURRENT
vs. INPUT VOLTAGE
600
500
400
300
200
100
0
0 0.5 1.0 1.5 2.0 2.5
INPUT VOLTAGE (V)
REFERENCE VOLTAGE vs.
TEMPERATURE
1.260
1.255
1.250
1.245
1.240
-40 -20
0 20 40 60
TEMPERATURE (°C)
80
1.253
1.252
1.251
1.250
1.249
1.248
1.247
0
REFERENCE VOLTAGE
vs. REFERENCE CURRENT
50 100 150 200
REFERENCE CURRENT (µA)
250
_______________________________________________________________________________________ 5
5 Page 
Digital Camera Step-Up
Power Supply
OUT
IC POWER
2.35V
ONM
REF
GND
OSC
FBM
COMPM
FB1
COMP1
DCON1
1.25V
FB2
COMP2
DCON2
FB3
COMP3
DCON3
AI
ON1
ON2
ON3
ONA
UNDERVOLTAGE LOCKOUT
EN
ON RDY
REFERENCE
REF
MAX1800
EN
STARTUP
OSCILLATOR
Q
MAIN PWM
CONTROLLER
D Q1
EN
OSCILLATOR
EN
OSC Q2
FB COMP
EN AUX1
OSC
FB Q
COMP
DUTY
EN AUX2
OSC
FB Q
COMP
DUTY
EN AUX3
OSC
FB Q
COMP
DUTY
GAIN
BLOCK
VREF EN
0.9VREF
POUT
POUT
P
LX
LX
N
PGND
PGND
DL1
DL2
DL3
AO
RDYM
N
Figure 2. Simplified Functional Diagram
the output voltage. The controller forces the inductor cur-
rent to rise above the 300mA Idle Mode threshold to
ensure pulse skipping and improved efficiency at light
loads.
Auxiliary DC-DC Controllers
The MAX1800 auxiliary controllers operate in a low-noise,
fixed-frequency, PWM mode, with output power limited by
the external components. The controllers regulate their out-
put voltages by modulating the pulse width of the drive sig-
nal for an external N-channel MOSFET switch. The auxiliary
controllers are inactive until the main output has started.
Figure 3 shows a block diagram for a MAX1800 auxil-
iary PWM controller. A sawtooth oscillator signal at OSC
governs the internal timing. At the beginning of each
cycle, DL_ goes high to turn on the external MOSFET
switch. The MOSFET switch turns off when the internally
level-shifted sawtooth rises above COMP_ or when the
maximum duty cycle is exceeded. The switch remains
off until the beginning of the next cycle. An internal
transconductance amplifier establishes an integrated
error voltage at COMP_, thereby increasing the loop
gain for improved regulation accuracy.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet MAX1800.PDF ] | |
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