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參數(shù)資料
| 型號： | MAX8621YETG |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 電源管理 |
| 英文描述： | Dual Step-Down DC-DC Power-Management ICs for Portable Devices |
| 中文描述： | 6-CHANNEL POWER SUPPLY SUPPORT CKT, QCC24 |
| 封裝： | 4 X 4 MM, 0.80 MM HEIGHT, THIN QFN-24 |
| 文件頁數(shù)： | 10/18頁 |
| 文件大?。?/td> | 360K |
| 代理商： | MAX8621YETG |
M
Dual Step-Down DC-DC Power-Management ICs
for Portable Devices
10
______________________________________________________________________________________
Detailed Description
The MAX8621Y/MAX8621Z power-management ICs are
designed specifically to power a variety of portable
devices including cellular handsets. Each device con-
tains two 4MHz high-efficient step-down converters, four
low-dropout linear regulators (LDOs), a 60ms (typ) reset
timer, a 200mA open-drain output driver, and power-
on/off control logic (Figure 3).
Step Down DC-DC Control Scheme
The MAX8621Y/MAX8621Z step-down converters are
optimized for high-efficiency voltage conversion over a
wide load range, while maintaining excellent transient
response, minimizing external component size, and
minimizing output voltage ripple. The DC-DC convert-
ers (BUCK1 and BUCK2) also feature an optimized on-
resistance internal MOSFET switch and synchronous
rectifier to maximize efficiency. The MAX8621Y/
MAX8621Z utilize a proprietary hysteretic-PWM control
scheme that switches with nearly fixed frequency up to
4MHz, allowing for ultra-small external components.
The step-down converter output current is guaranteed
up to 500mA, while consuming 40μA (typ).
When the step-down converter output voltage falls below
the regulation threshold, the error comparator begins a
switching cycle by turning the high-side p-channel
MOSFET switch on. This switch remains on until the mini-
mum on-time (t
ON
) expires and the output voltage is in
regulation or the current-limit threshold (I
LIMP
) is exceed-
ed. Once off, the high-side switch remains off until the
minimum off-time (t
OFF
) expires and the output voltage
again falls below the regulation threshold. During this off
period, the low-side synchronous rectifier turns on and
remains on until either the high-side switch turns on or
the inductor current reduces to the rectifier-off current
threshold (I
LXOFF
= 45mA (typ)). The internal synchro-
nous rectifier eliminates the need for an external
Schottky diode.
Voltage-Positioning Load Regulation
The MAX8621Y/MAX8621Z use a unique step-down
converter feedback network. By taking feedback from
the LX node through R1, the usual phase lag due to the
output capacitor is removed, making the loop exceed-
ingly stable and allowing the use of a very small ceramic
output capacitor. This configuration causes the output
voltage to shift by the inductor series resistance multi-
plied by the load current. This output voltage shift is
known as voltage-positioning load regulation. Voltage-
positioning load regulation greatly reduces overshoot
during load transients, which effectively halves the
peak-to-peak output-voltage excursions compared to
traditional step-down converters. See the Buck1 Load-
Transient Response graph in the
Typical Operating
Characteristics
.
Low-Dropout Linear Regulators
Each MAX8621Y/MAX8621Z contains four low-dropout,
low-quiescent-current, high-accuracy linear regulators
(LDOs). OUT1 and OUT2 supply loads up to 300mA,
while OUT3 and OUT4 supply loads up to 150mA. The
LDO output voltages are set using SEL1 and SEL2 (see
Table 1). The LDOs include an internal reference, error
amplifier, p-channel pass transistor, internal program-
mable voltage-divider, and an OUT1 power-good com-
parator. Each error amplifier compares the reference
voltage to a feedback voltage and amplifies the differ-
ence. If the feedback voltage is lower than the refer-
ence voltage, the pass-transistor gate is pulled lower,
allowing more current to pass to the outputs and
increasing the output voltage. If the feedback voltage is
too high, the pass-transistor gate is pulled up, allowing
less current to pass to the output.
DR Driver
Each MAX8621Y/MAX8621Z includes a 1.3
Ω
n-channel
MOSFET open-drain output that is controlled by ENDR.
This output can be used to drive LEDs (see the
Typical
Operating Circuit
) and allow adjustable output voltages
(see Figure 1).
Programming LDO Output Voltages
(SEL1, SEL2)
As shown in Table 1, the LDO output voltages, OUT1,
OUT2, OUT3, and OUT4 are pin-programmable by the
logic states of SEL1 and SEL2. SEL1 and SEL2 are
trilevel inputs: IN, open, and GND. The input voltage,
V
IN
, must be greater than the selected OUT1, OUT2,
OUT3, and OUT4 voltages. The logic states of SEL1
and SEL2 can be programmed only during power-up.
Once the OUT_ voltages are programmed, their values
do not change by changing SEL_ unless the
MAX8621Y/MAX8621Z power is cycled.
MAX8621Y
MAX8621Z
L1
2.2
μ
H
C6
150pF
R2
115k
Ω
R1
150k
Ω
R5
215k
Ω
DR
FB1
LX1
BUCK1
1.38V OR 1.8V
ENDR
1.38/1.8
Figure 1. Adjusting BUCK1 Output Voltage Using DR
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8621YETG+ | 功能描述:PMIC 解決方案 Dual Step-Down PMIC for Portable Devices RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| MAX8621YETG+T | 功能描述:PMIC 解決方案 Dual Step-Down PMIC for Portable Devices RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| MAX8621YETG-T | 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| MAX8621ZETG | 功能描述:PMIC 解決方案 Dual Step-Down PMIC for Portable Devices RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| MAX8621ZETG+ | 功能描述:PMIC 解決方案 Dual Step-Down PMIC for Portable Devices RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
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