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| 型号： | MAX1637EEE |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 100 |
| PWM 型： | 电流模式，混合 |
| 输出数： | 1 |
| 频率 - 最大： | 338kHz |
| 占空比： | 96% |
| 电源电压： | 3.15 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
Miniature, Low-Voltage,
Precision Step-Down Controller
REF, V CC , and V GG Supplies
The 1.100V reference (REF) is accurate to ±2% over
temperature, making REF useful as a precision system
reference. Bypass REF to GND with a 0.22μF (min)
capacitor. REF can supply up to 50μA for external
loads. Loading REF reduces the main output voltage
slightly because of the reference load-regulation error.
The MAX1637 has two independent supply pins, V CC
and V GG . V CC powers the sensitive analog circuitry of
the SMPS, while V GG powers the high-current MOSFET
drivers. No protection diodes or sequencing require-
ments exist between the two supplies. Isolate V GG from
V CC with a 20 Ω resistor if they are powered from the
same supply. Bypass V CC to GND with a 0.1μF capaci-
tor located directly adjacent to the pin. Use only small-
signal diodes for the boost circuit (10mA to 100mA
Schottky or 1N4148 diodes are preferred), and bypass
V GG to PGND with a 4.7μF capacitor directly at the
package pins. The V CC and V GG input range is 3.15V
to 5.5V.
High-Side Boost Gate Drive (BST)
Gate-drive voltage for the high-side N-channel switch is
generated by a flying-capacitor boost circuit (Figure 2).
The capacitor between BST and LX is alternately
charged from the V GG supply and placed parallel to
the high-side MOSFET’s gate-source terminals.
On start-up, the synchronous rectifier (low-side
MOSFET) forces LX to 0V and charges the boost
capacitor to V GG . On the second half-cycle, the SMPS
turns on the high-side MOSFET by closing an internal
switch between BST and DH. This provides the neces-
sary enhancement voltage to turn on the high-side
switch, an action that boosts the gate-drive signal
above the battery voltage.
Ringing at the high-side MOSFET gate (DH) in discon-
tinuous-conduction mode (light loads) is a natural oper-
ating condition. It is caused by residual energy in the
tank circuit, formed by the inductor and stray capaci-
tance at the switching node, LX. The gate-drive nega-
tive rail is referred to LX, so any ringing there is directly
If the circuit is operating in continuous-conduction
mode, the DL drive waveform is simply the complement
of the DH high-side-drive waveform (with controlled
dead time to prevent cross-conduction or “shoot-
through”). In discontinuous (light-load) mode, the syn-
chronous switch is turned off as the inductor current
falls through zero.
Shutdown Mode and Power-On Reset
SHDN is a logic input with a threshold of about 1.5V
that, when held low, places the IC in its 0.5μA shut-
down mode. The MAX1637 has no power-on-reset cir-
cuitry, and the state of the device is not known on initial
power-up. In applications that use logic to drive SHDN ,
it may be necessary to toggle SHDN to initialize the
part once V CC is stable. In applications that require
automatic start-up, drive SHDN through an external RC
network (Figure 5). The network will hold SHDN low
until V CC stabilizes. Typical values for R and C are 1M Ω
and 0.01μF. For slow-rising V CC , use a larger capacitor.
When cycling V CC , V CC must stay low long enough to
discharge the 0.01μF capacitor, otherwise the circuit
may not start. A diode may be added in parallel with
the resistor to speed up the discharge.
Current-Limiting and Current-
Sense Inputs (CSH and CSL)
The current-limit circuit resets the main PWM latch and
turns off the high-side MOSFET switch whenever the
voltage difference between CSH and CSL exceeds
100mV. This limiting is effective for both current flow
directions, putting the threshold limit at ±100mV. The
tolerance on the positive current limit is ±20%, so the
external low-value sense resistor (R1) must be sized for
80mV / I PEAK , where I PEAK is the peak inductor current
required to support the full load current. Components
must be designed to withstand continuous current
stresses of 120mV / R1.
V IN
coupled to the gate-drive output.
R
V GG
V CC
Synchronous-Rectifier Driver (DL)
Synchronous rectification reduces conduction losses in
the rectifier by shunting the normal Schottky catch
diode with a low-resistance MOSFET switch. Also, the
synchronous rectifier ensures proper start-up of the
boost gate-driver circuit. If the synchronous power
MOSFET is omitted for cost or other reasons, replace it
with a small-signal MOSFET, such as a 2N7002.
SHDN
C
MAX1637
R = 1M Ω
C = 0.01 μ F
Figure 5. Power-On Reset RC Network for Automatic Start-Up
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1637EEE+ | 功能描述:DC/DC 开关控制器 Mini Precision Step Down RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1637EEE+T | 功能描述:DC/DC 开关控制器 Mini Precision Step Down RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1637EEE-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1637EVKIT | 制造商:Maxim Integrated Products 功能描述:MINIATURE, LOW-VOLTAGE, PRECISION STEP-DOWN C - Bulk |
| MAX1638BEAG | 制造商:MAX 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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