- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385522 > MAX1802EHJ (MAXIM INTEGRATED PRODUCTS INC) Digital Camera Step-Down Power Supply PDF資料下載
參數(shù)資料
| 型號： | MAX1802EHJ |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Digital Camera Step-Down Power Supply |
| 中文描述： | 0.75 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQFP32 |
| 封裝： | 5 X 5 MM, 1 MM HEIGHT, TQFP-32 |
| 文件頁數(shù)： | 14/28頁 |
| 文件大?。?/td> | 469K |
| 代理商： | MAX1802EHJ |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁當(dāng)前第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁
M
Digital Camera Step-Down
Power Supply
14
______________________________________________________________________________________
Detailed Description
The MAX1802 typical application circuit is shown in
Figure 1. It features two step-down DC-DC converters
(main and core), three auxiliary step-up DC-DC con-
trollers, and control capability for multiple external
MAX1801 slave DC-DC controllers. Together, these
provide a complete high-efficiency power-supply solu-
tion for digital still cameras. Figures 2 and 3 show the
MAX1802 functional block diagrams.
Master-Slave Configuration
The MAX1802 supports MAX1801
“
slave
”
controllers
that obtain input power, a voltage reference, and an
oscillator signal directly from the MAX1802
“
master
”
DC-DC converter. The master-slave configuration
reduces system cost by eliminating redundant circuitry
and controlling the harmonic content of noise with syn-
chronized converter switching.
Main DC-DC Converter
The MAX1802 main step-down DC-DC converter gen-
erates a 2.7V to 5.5V output voltage from a 2.5V to 11V
battery input voltage. When the battery voltage is lower
than the main regulation voltage, the regulator goes
into dropout and the P-channel switch remains on. In
this condition, the output voltage is slightly lower than
the input voltage. The converter drives an external P-
channel MOSFET power switch and an external N-
channel MOSFET synchronous rectifier. The converter
operates in a low-noise, constant-frequency PWM cur-
rent mode to regulate the voltage across the load.
Switching harmonics generated by fixed-frequency
operation are consistent and easily filtered.
The external P-channel MOSFET switch turns on during
the first part of each cycle, allowing current to ramp up
in the inductor and store energy in a magnetic field
while supplying current to the load. During the second
part of each cycle, the P-channel MOSFET turns off and
the voltage across the inductor reverses, forcing cur-
rent through the external N-channel synchronous rectifi-
er to the output filter capacitor and load. As the energy
stored in the inductor is depleted, the current ramps
down. The synchronous rectifier turns off when the
inductor current approaches zero or at the beginning of
a new cycle, at which time the P-channel switch turns
on again.
The current-mode PWM converter uses the voltage at
COMPM to program the inductor current and regulate
the output voltage. The converter detects inductor cur-
rent by sensing the voltage across the source and
drain of the external P-channel MOSFET. The MAX1802
main output switches to Idle Mode at light loads to
improve efficiency by leaving the P-channel switch on
until the voltage across the MOSFET reaches the 20mV
Idle Mode threshold. The Idle Mode current is 20mV
divided by the MOSFET on-resistance. By forcing the
inductor current above the Idle Mode threshold, more
energy is supplied to the output capacitor than is
required by the load. The switch and synchronous rec-
tifiers then remain off until the output capacitor dis-
charges to the regulation voltage. This causes the
converter to operate at a lower effective switching fre-
quency at light loads, thus improving efficiency.
An internal comparator turns off the N-channel synchro-
nous rectifier as the inductor current drops near zero,
by measuring the voltage across the MOSFET. If the N-
channel MOSFET on-resistance is low (less than that of
the P-channel switch), it may cause the MOSFET to turn
off prematurely, degrading efficiency. This is especially
critical for high input voltage applications, such as with
2 series Li+ cells. In this case, use an N-channel MOS-
FET with greater on-resistance than the P-channel
switch, and/or place a Schottky recitifier across the N-
channel MOSFET gate-source.
The voltage at COMPM is typically clamped to
V
COMPM(MAX)
= 2.14V, thereby limiting the inductor
current. The peak inductor current (I
LIM
) and the maxi-
mum average output current (I
OUT(MAX)
) are deter-
mined by the following equations:
where A
VSWM
is the main slope compensation gain
(0.20V/V), A
VCSM
is the voltage gain of the main cur-
rent-sense amplifier (9.3V/V), R
DSP
is the on-resistance
of the external P-channel MOSFET switch, and L is the
inductor value. Note that the current limit increases as
the input/output voltage ratio increases.
I
V
V
V
A
V
IN
A
R
I
I
V
V
f
V
L
LIM
COMPM MAX
REF
OUT
VSWM
VCSM
DSP
OUT MAX
(
LIM
OUT
IN
2
OUT
OSC
=
+
=
(
)
)
1
1
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX1804 | External Four-Input Feedback Integrator for Power Supplies |
| MAX1804EUB | External Four-Input Feedback Integrator for Power Supplies |
| MAX1809 | 3A, 1MHz, DDR Memory Termination Supply |
| MAX1809EEE | 3A, 1MHz, DDR Memory Termination Supply |
| MAX1809ETI | 3A, 1MHz, DDR Memory Termination Supply |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1802EHJ+ | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1802EHJ+T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1802EHJ-T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1804EUB | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| MAX1804EUB+ | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 Feedback Integrator for Power Supply RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。