HT7886 datasheet(8/18 Pages) HEROIC

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HT7886

Buck Converter

-8-

8/2023 – V1.2

◼ APPLICATION INFORMATION

1 Hysteresis Current Control with Adaptive Threshold Adjustment

The HT7886 operates in a hysteretic voltage-control mode to

regulate the output voltage. FB is connected to the tap of a

resistor divider, which determines the output voltage. The

power MOSFET is turned on when the FB voltage (VFB) drops

to 185mV and remains on until VFB rises to 215mV. The power

MOSFET is turned off when VFB rises to 215mV and remains

off until VFB falls to 185mV. The two thresholds of 215mV and

185mV are adjusted adaptively to compensate for all the

circuit delays, so the output voltage is regulated with an

average 200mV value at FB.

HT7886 在滞后电压控制模式下工作，以调

节输出电压。

FB 连接到电阻分压器的中间，电

阻分压器决定输出电压。当

FB 电压（VFB）降

至

185mV 时，功率 MOSFET 开启，并保持开

启状态，直到

VFB 升至 215mV。当 VFB 上升到

215mV 时，功率 MOSFET 关闭，并保持关闭状

态，直到

VFB 下降到 185mV。215mV 和 185mV

的两个阈值自适应调整，以补偿所有电路延迟，

因此输出电压在

FB 处以平均 200mV 值调节。

2 Enable (EN) Control

The HT7886 has a dedicated enable control pin (EN) with

positive logic. Its falling threshold is 1.3V, and its rising

threshold is 1.7V.

When floating, EN is pulled up to about 2.5V by an internal

2µA current source, so it is enabled. A current over 2µA is

needed to pull EN down.

HT7886 的 EN 脚高电平有效，控制芯片使

能。其下降阈值为

1.3V，上升阈值为 1.7V。

悬空时，

EN 被内部 2µA 电流源拉高至约

2.5V，芯片使能。需要超过 2µA 的电流才能将

EN 下拉。

3 Floating Driver and Bootstrap Charging

The floating power MOSFET driver is powered by an external

bootstrap capacitor. This floating driver has its own under-

voltage lockout (UVLO) protection. The UVLO rising

threshold is 2.2V with a hysteresis of 150mV.

The bootstrap capacitor is charged and regulated to about 5V

by the dedicated internal bootstrap regulator.

功率

MOSFET 驱动由外部自举电容器供电。

该功率管有其自身的欠压锁定（

UVLO）保护。

UVLO 上升阈值为

。

内部自举调节器通过外部自举电容充电调

节至约

5V。

4 Under-Voltage Lockout (UVLO)

Under-voltage lockout (UVLO) is implemented to protect the

chip from operating at an insufficient supply voltage. The

UVLO rising threshold is about 4V, while its falling threshold

is a consistent 3.6V.

欠压锁定（

UVLO）功能可避免芯片工作在

电源电压不足的条件。

UVLO 上升阈值约为 4.7V，

下降阈值为

4.4V

5 Dimming Function for LED

Because the FB reference of the HT7886 is very low, it is

recommended to use the HT7886 for LED drivers by

connecting the LED current sense resistor between FB and

GND. In such applications, the HT7886 uses DIM for

dimming. To achieve dimming, apply a pulse on DIM. The

high level of the pulse should be >1.5V, and the low level

should be <0.5V. The frequency can be as high as 20kHz.

由于

HT7886 的 FB 参考极低，将 HT7886

用于

LED 驱动器时，建议在 FB 和 GND 之间连

接

LED 电流感应电阻器。在此类应用中，

HT7886 使用 DIM 进行调光。要实现调光，在

DIM 引脚上加脉冲信号。脉冲的高电平应大于

1.5V，低电平应小于 0.5V。频率可高达 20kHz。

6 Thermal Shutdown

Thermal shutdown is implemented to prevent the chip from

operating at exceedingly high temperatures. When the silicon

die temperature is higher than its upper threshold, the entire

chip shuts down. When the temperature is lower than its lower

threshold, the chip is enabled again.

过热关断保护是为了防止芯片在极高的温

度下工作。当芯片温度高于其上限阈值时，整个

芯片关闭。当温度低于其下限阈值时，芯片再次

启用。

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